Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
techtalk:evo:carb02 [2020/01/22 05:54]
ixl2relax [Diagnosing CV Carb Issues]
techtalk:evo:carb02 [2020/09/18 03:14] (current)
ixl2relax [Enrichener Function (Choke)]
Line 9: Line 9:
 **Design Info** **Design Info**
  
-From 1989-later, the carburetor installed on Sportsters was made by Keihin. It has a 40mm maximum venturi, but the design of the constant-velocity carb utilizes a vacuum-operated slide to vary the venturi opening to help maintain a good air velocity throughout the carbs operating range.+From 1989-later, the carburetor installed on Sportsters was made by Keihin. It has a 40mm maximum venturi, but the design of the constant-velocity carb utilizes a vacuum-operated slide to vary the venturi opening to help maintain a proper ​air velocity throughout the carbs operating range.
  
-The CV40 uses a gravity-fed fuel supply through a float controlled inlet valve to fill a fuel supply bowl, from which the internal jets obtain fuel. It also has an enrichment system ​(mislabeled choke) that provides a pathway for fuel to bypass the carb and be supplied directly into the manifold for better starting.+The CV40 uses a gravity-fed fuel supply through a float controlled inlet valve to fill a fuel supply bowl, from which the internal jets obtain fuel. It also has an enrichment systemmislabeled ​choke. This provides a pathway for fuel to bypass ​most of the carb operation ​and be supplied directly into the manifold, at the rear of the carb, for better starting.
  
 There are a number of parts that operate in combination to control the mixing of fuel & air into a combustible fuel mixture. The vacuum slide, needle, main jet, slow jet, idle mixture screw, idle ports, tranfer ports and accelerator pump, all assist in this mixing operation over the range of operating conditions. There are a number of parts that operate in combination to control the mixing of fuel & air into a combustible fuel mixture. The vacuum slide, needle, main jet, slow jet, idle mixture screw, idle ports, tranfer ports and accelerator pump, all assist in this mixing operation over the range of operating conditions.
  
-The constant-velocity system provides a partial means of compensating for operation at different altitudes. In a fixed system, as altitude increases, the fuel mixture becomes richer due to the thinner air. But the CV system partially compensates for this fact because the vacuum-slide oparation is also affected by the thiner ​air, thereby supplying less fuel into the mix.+The purpose of the carburetor is to atomize fuel into the incoming air such that a proper air-fuel-ratio (AFR) is achieved for varying conditions. The Pilot & Main Jets each use an emulsion tube with a fuel orifice & air holes. Each emulsion tube pulls fuel from the float bowl reserve and is fed air thru small air ports (called air jets) on the face of the carb (filter side). In each case, the emulsion tube produces an air/fuel mixture that is further mixed with the air flowing into the venturi (carburetor throat). 
 + 
 +The air flow is generally controlled by the Throttle Plate along with the vertically moving slide that essentially varies the venturi size to create a Constant Velocity of air (from which it gets it's name). By selecting various Pilot and Main Jets, the AFR can be altered to produce a preferred ratio. Air flowing into the venturi creates a vacuum which pulls the air/fuel mixture from the emulsion tubes into the air stream. 
 + 
 +To create a proper idle operation, the Idle Port (on the engine side of the throttle plate) has a separate adjustable screw that allows some of the mixture from the Pilot Jet emulsion tube to be bled directly into the manifold, bypassing the throttle plate. 
 + 
 +As the throttle plate is opened, fuel is pulled from the Transfer Ports. With more throttle, fuel is pulled thru the needle jet, in greater quantity as the tapered needle is lifted out of the needle jet opening by the vacuum-operated slide. 
 + 
 +The constant-velocity system provides a partial means of compensating for operation at different altitudes. In a fixed system, as altitude increases, the fuel mixture becomes richer due to the thinner air. But the CV system partially compensates for this fact because the vacuum-slide oparation is also affected by the thinner ​air, thereby supplying less fuel into the mix.
  
 The CV40 (1989-later) has an accelerator pump, controlled by a rod attached to the throttle cable cam, to provide additional fuel when the throttle is quickly opened for acceleration. It squirts raw fuel into the venturi throat to enhance the fuel mixture along with the quickly added air. The CV40 (1989-later) has an accelerator pump, controlled by a rod attached to the throttle cable cam, to provide additional fuel when the throttle is quickly opened for acceleration. It squirts raw fuel into the venturi throat to enhance the fuel mixture along with the quickly added air.
  
-The carb has been adjusted to control exhaust emissions. The idle mixture is set at the factory and the adjusting screw is capped because it is not to be adjusted except by factory technicians.+The carb has been adjusted to control exhaust emissions. The idle mixture is set at the factory and the adjusting screw is capped because it is not to be adjusted except by factory technicians. The cap can be removed and adjustments can be made.
  
-Note from the service manual: Adjusting mixture setting by procedures other than specified in this section may be in violation of local regulations.+However, note this from the service manual ​(FYI): Adjusting mixture setting by procedures other than specified in this section may be in violation of local regulations.
  
 \\ \\
Line 100: Line 108:
 ==== Why Not Dynojet Kits? ==== ==== Why Not Dynojet Kits? ====
  
-{{  :​techtalk:​evo:​carb:​cv40-needle-em-jets.jpg?​360| Photo by IXL2Relax at the XLForum}} 
 The "​DynoJet"​ kits (and many equivalent ones) can be an issue. Typically, they replace the factory needle, emulsion tube, main jet & diaphragm/​slide spring. They also recommend that you drill the slide vacuum hole out for quicker throttle response. The DynoJet emulsion tube and main jets are not compatible with the Keihin emulsion tube/jets - they use different threads. There are even FAKE Dynojet kits that have shown up on the market, presumably from China ((Fake DJ Kit - https://​www.dynojet.com/​warnings/​PressReleaseKnockOffJetKits.pdf)) The "​DynoJet"​ kits (and many equivalent ones) can be an issue. Typically, they replace the factory needle, emulsion tube, main jet & diaphragm/​slide spring. They also recommend that you drill the slide vacuum hole out for quicker throttle response. The DynoJet emulsion tube and main jets are not compatible with the Keihin emulsion tube/jets - they use different threads. There are even FAKE Dynojet kits that have shown up on the market, presumably from China ((Fake DJ Kit - https://​www.dynojet.com/​warnings/​PressReleaseKnockOffJetKits.pdf))
  
Line 110: Line 117:
   * Check the Slide Vacuum Port Hole (not the center hole): Stock is .097" - DJ is .136" (Is the hole smaller or larger than 7/64" drill bit?)   * Check the Slide Vacuum Port Hole (not the center hole): Stock is .097" - DJ is .136" (Is the hole smaller or larger than 7/64" drill bit?)
   * Check the Main Emulsion Tube : Stock has 2x2Hi+4x3Lo Emulsion Holes - DJ uses only 2Lo Holes   * Check the Main Emulsion Tube : Stock has 2x2Hi+4x3Lo Emulsion Holes - DJ uses only 2Lo Holes
-{{  :​techtalk:​evo:​carb:​cv40-needle-jet.jpg?​200| Annotated by IXL2Relax at the XLForum}} +  ​* The stock Keihin Emulsion Tube uses 6mm-threaded ​Main Jets - The DJ one takes only 5mm-threaded ​jets, which are incompatible with the Keihin tube and only available from DJ
-  ​* The stock Keihin Emulsion Tube uses 6mm Main Jets - The DJ one takes only 5mm jets, which are incompatible with the Keihin tube and only available from DJ+
  
 Here's the Dynojet Fraud Alert Press Release regarding counterfeit jet kits:\\ Here's the Dynojet Fraud Alert Press Release regarding counterfeit jet kits:\\
 {{ :​techtalk:​evo:​carb:​dynojet-pressrelease-knockoffjetkits.pdf |}} {{ :​techtalk:​evo:​carb:​dynojet-pressrelease-knockoffjetkits.pdf |}}
  
-While some people have had satisfactory results with the DJ kits, if you are having trouble getting a good tune on the carb, remove all DJ items and restore the carb to Keihin parts including buying another slide if it's been drilled. The stock parts are good quality and will provide excellent operation if the carb is tuned properly. ((the opinion of many on the XLForum))+While some people have had satisfactory results with the DJ kits, if you are having trouble getting a good tune on the carb, remove all DJ items and restore the carb to Keihin parts including buying another slide if it's been drilled. The stock parts are good quality and will provide excellent operation if the carb is tuned properly. ((the opinion of many on the XLForum)) ​See the paragraphs above about 'Some Tuning Considerations'​.
  
 \\ \\
 +
 +==== CV40 Needle, Jets & Idle Mixture Screw Parts ====
 +
 +|  **Here are the genuine Keihin CV40 parts.\\ \\ Check your parts to be sure they match.** ​ | Be sure the Needle Jet is installed with\\ the long side up into the carb throat. | These are the parts for the\\ Idle Mixture Screw (IMS).\\ Install in correct order. |
 +| {{:​techtalk:​evo:​carb:​cv40-needle-em-jets.jpg?​360| Photo by IXL2Relax at the XLForum}} | {{:​techtalk:​evo:​carb:​cv40-needle-jet.jpg?​200| Annotated by IXL2Relax at the XLForum}} | {{:​techtalk:​evo:​carb:​cv-idlemixscrew.jpg?​150| }} |
  
 From the factory, there is a cap over the Idle Mixture Screw. This needs to be removed to make IMS adjustments during tuning. It does not need to be replaced when done, but the cap is available as HD P/N 28015-01 if you would like to replace it when done making changes.((IMS Cap - http://​xlforum.net/​forums/​showpost.php?​p=595622&​postcount=9)) From the factory, there is a cap over the Idle Mixture Screw. This needs to be removed to make IMS adjustments during tuning. It does not need to be replaced when done, but the cap is available as HD P/N 28015-01 if you would like to replace it when done making changes.((IMS Cap - http://​xlforum.net/​forums/​showpost.php?​p=595622&​postcount=9))
  
-{{  :​techtalk:​evo:​carb:​cv-idlemixscrew.jpg?​150| }} 
 The Idle Mixture Screw "​packing"​ (spring, washer, o-ring) and the screw itself was never meant to be removed or tampered with, according to the MoCo, due to EPA regulations. This was adjusted and the screw covered with a soft aluminum cap at the factory before initial installation on your bike. None of these packing items are offered as replacement parts from your HD dealer, so you will need to look to the aftermarket suppliers for parts. The Idle Mixture Screw "​packing"​ (spring, washer, o-ring) and the screw itself was never meant to be removed or tampered with, according to the MoCo, due to EPA regulations. This was adjusted and the screw covered with a soft aluminum cap at the factory before initial installation on your bike. None of these packing items are offered as replacement parts from your HD dealer, so you will need to look to the aftermarket suppliers for parts.
  
Line 205: Line 215:
     * Be sure to reinstall pump rod correctly     * Be sure to reinstall pump rod correctly
   * Be sure you have removed each part, cleaned the ports & reinstalled correctly   * Be sure you have removed each part, cleaned the ports & reinstalled correctly
-  * Set the Idle Set Screw (located on the right side of the carb, near the throttle cables)\\ so that the Throttle Plate is between the Idle Port (one hole in the carb throat) and the\\ Transfer Ports (which consists of 5 holes nearby)+  * Set the Idle Set Screw (located on the right side of the carb, near the throttle cables)\\ so that the Throttle Plate is closed as much as possible. Try getting it between the Idle Port\\ (one hole in the carb throat) and the Transfer Ports (which consists of 5 holes nearby).\\ Don't obssess over it if you can'​t. 
 + 
 +\\ 
 + 
 + 
 +==== Setting The Float Level =====
  
-**Click on the small image below for the detailed instructions regarding setting the float level:**\\ 
 (Using a 1/2-inch spacer to lift the float side of the carb will approximate the 15°-20° angle needed.)\\ (Using a 1/2-inch spacer to lift the float side of the carb will approximate the 15°-20° angle needed.)\\
-{{:​techtalk:​evo:​carb:​hd-cv40-floatlevel-instructions.jpg?​100|}}{{:​techtalk:​evo:​carb:​hd-cv40-floatlevel.jpg|}}+{{:​techtalk:​evo:​carb:​hd-cv40-floatlevel-instructions.jpg?​250|}}{{:​techtalk:​evo:​carb:​hd-cv40-floatlevel.jpg|}}\\ 
 +**Click on the small image above for the detailed**\\ 
 +**instructions regarding setting the float level:** 
 + 
 +{{:​techtalk:​evo:​carb:​cv40-floatvalve-02.jpg?​300|}}{{:​techtalk:​evo:​carb:​cv40-floatvalve-01.jpg?​400|}} 
 + 
 +In [[http://​xlforum.net/​forums/​showthread.php?​t=2074492|This XLForum Thread]] there is a discussion of the float bowl overflowing and the possibility that it is caused by aftermarket float valves that are not of the proper design.((Images above by Hippysmack of the XLForum)) 
 + 
 +** Tip for Inspecting Float Level - With Carb Installed ** 
 +  
 +HD advised of a tip for adjusting the float level thru Tech Tip #36 dated September 1993. \\ 
 +However, this only works if you have an overflow fitting on the bowl (carbs for 1200S models don't have this fitting). \\  
 +  * Checking carburetor float level can be easily done without even removing the carburetor from the motorcycle. 
 +  * Simply attach a section of clear model airplane fuel line to the float bowl overflow fitting. 
 +  * A small diameter fuel line, which is compatible with gasoline, can be found in most hobby supply shops. 
 +  * Route the hose upward alongside the carburetor body. 
 +  * The motorcycle must be held level and be running to perform this test. 
 +  * Open the float bowl drain screw and fuel will rise in the hose to the same level as that in the bowl itself. 
 +  * In a carb with a properly adjusted float level the fuel level in this hose will be at the joint between the carb body and the float bowl face. 
 + 
 +\\
  
  
Line 216: Line 250:
   * Check intake seals on manifold (at heads) - replace now while it's apart   * Check intake seals on manifold (at heads) - replace now while it's apart
   * Check intake seal between manifold & carb - replace now   * Check intake seal between manifold & carb - replace now
-  * Minimize Throttle Plate opening at idle - Set it between Idle Port & Transfer Ports [[http://​xlforum.net/​forums/​showthread.php?​t=1635658|(See this XLForum thread)]]+  * Minimize Throttle Plate opening at idle - Set it between Idle Port & Transfer Ports if possible ​[[http://​xlforum.net/​forums/​showthread.php?​t=1635658|(See this XLForum thread)]]
   * Check Idle Mixture Screw (IMS) screw/​spring/​washer/​o-ring condition - clean port   * Check Idle Mixture Screw (IMS) screw/​spring/​washer/​o-ring condition - clean port
   * Check IMS seat (Has the screw needle tip deformed the hole?)   * Check IMS seat (Has the screw needle tip deformed the hole?)
Line 222: Line 256:
  
 \\ \\
 +
  
 ==== Change the Screws ==== ==== Change the Screws ====
Line 321: Line 356:
 ( See this [[http://​xlforum.net/​forums/​showthread.php?​t=165259|XLForum Thread]] on needle dimensions) ( See this [[http://​xlforum.net/​forums/​showthread.php?​t=165259|XLForum Thread]] on needle dimensions)
  
-**Emulsion ​Tubes** ((stevo of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2876)):​ - As the throttle plate is opened further the main circuit comes into play. Fuel enters the bottom of the emulsion tube thru the main jet. Air enters thru the main air bleed jet in the front of the carb. The air and fuel are mixed into an emulsion ​in the emulsion tube before ​it passes up the tube past the needle jet and needle into the carb venturi and down the intake chasing after (combining with) the idle circuit fuel. The size, number and position of the holes in the emulsion tube effect the fuel delivery. More holes = more air = leaner mixture. More holes at the top = leaner mixture at low speeds. More holes at the bottom = leaner mixture at high speeds. If you change emulsion tubes you need to use a compatible needle. It will also have an effect on the main jet size (at WOT) and quite often the pilot circuit thru the just-off-idle response. Needles, needle jet, emulsion tube (size, position and amount of holes), main air bleed size and main jet are all closely linked. Changing one can affect the others and all have an affect on the fuel delivery to differing amount at different throttle positions.+**Emulsion ​Tube** ((stevo of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2876)):​ - As the throttle plate is opened further the main circuit comes into play. Fuel enters the bottom of the emulsion tube thru the main jet. Air enters thru the main air bleed jet in the front of the carb. The air and fuel are mixed in the emulsion tube before ​this fuel mixture ​passes up the tube past the needle jet and needle into the carb venturi and down the intake chasing after (combining with) the idle circuit fuel mix. The size, number and position of the holes in the emulsion tube effect the fuel delivery. More holes = more air = leaner mixture. More holes at the top = leaner mixture at low speeds. More holes at the bottom = leaner mixture at high speeds. If you change emulsion tubes you need to use a compatible needle. It will also have an effect on the main jet size (at WOT) and quite often the pilot circuit thru the just-off-idle response. Needles, needle jet, emulsion tube (size, position and amount of holes), main air bleed size and main jet are all closely linked. Changing one can affect the others and all have an affect on the fuel delivery to differing amount at different throttle positions.
  
  
-**Throttle Plate** - To assure the throttle plate is capable of closing completely, back out the idle set screw (on the side of the carb near the throttle cable cam) so that it is not limiting the closing of the throttle plate. ​Carefully loosen the two throttle plate mounting screws, slightly. After the throttle plate is fully closed and has centered itself in the venturi, retighten the two mounting screws (don't overtighten & strip the threads). ​Make sure the throttle plate rotates smoothly with the throttle cable cam. Set the position of the throttle plate, with the idle set screw, so that the bottom edge of the plate is closed just past the transfer port holes and is thus located between the single idle port hole and the multiple holes of the transfer ports. In practice, this is easier on some CV40 carbs than others. Do what you can to keep the plate as closed as possible, but don't obssess ​on getting it exactly between those port holes. Your viewing angle is skewed when looking in there, anyway.+**Throttle Plate** - To assure the throttle plate is capable of closing completely, back out the idle set screw (on the side of the carb near the throttle cable cam) so that it is not limiting the closing of the throttle plate.Make sure the throttle plate rotates smoothly with the throttle cable cam. Set the position of the throttle plate, with the idle set screw, so that the bottom edge of the plate is closed ​as much as possible for setting the idle operation. Try getting it just past the transfer port holes and thus located between the single idle port hole and the multiple holes of the transfer ports. In practice, this is easier on some CV40 carbs than others. Do what you can to keep the plate as closed as possible, but DON'T OBSSESS ​on getting it exactly between those port holes. Your viewing angle is skewed when opening the throttle plate and looking in the venturi, anyway, so you see the hole before the plate is completely beyond it.
  
-(If by chance, for any reason, you have the throttle plate completely off, be aware that there is a right & wrong way to reinstall it. Be sure the plate is remounted with the right orientation because the top & bottom have an angled edge that needs to properly meet the carb venturi.)+(* It doesn'​t happen often, but if the throttle plate appears not to close fully with the idle screw fully wound out, it may need to be recentered in the throat. Carefully loosen the two throttle plate mounting screws, slightly. After the throttle plate is fully closed and has centered itself in the venturi, start to retighten the two mounting screws (don't overtighten & strip the threads) while opening & closing the throttle so the plate squares up with the shaft but also recenters in the venturi. ​If by chance, for any reason, you have the throttle plate completely off, be aware that there is a right & wrong way to reinstall it. Be sure the plate is remounted with the right orientation because the top & bottom have an angled edge that needs to properly meet the carb venturi.)
  
 {{ :​techtalk:​evo:​carb:​cv40-imscap-drillbit.jpg?​200|}} {{ :​techtalk:​evo:​carb:​cv40-imscap-drillbit.jpg?​200|}}
Line 335: Line 370:
 **INTERACTIONS OF JETS & PORTS - A balancing act** **INTERACTIONS OF JETS & PORTS - A balancing act**
  
-The Slow Jet (AKA: Pilot Jet) along with the Idle Mixture Screw (IMS) determine ​the quantity & quality of the Idle Fuel Mix, while the Slow Jet alone determines the Transfer Fuel Mix. It is an important balancing chore to get all the parts involved in the Idle & Transfer functions to work well together to meet the needs of the engine operating range. As you change one part or setting, it may require making changes in other settings in order to keep or find the proper balance of the different fuel circuits. This balancing concept also applies to the mid-range and wide-open-throttle operations.+The Slow Jet (AKA: Pilot Jet or Idle Jet) along with the Idle Mixture Screw (IMS) determines ​the quantity & quality of the Idle Fuel Mix, while the Slow Jet alone determines the Transfer Fuel Mix. It is an important balancing chore to get all the parts involved in the Idle & Transfer functions to work well together to meet the needs of the engine operating range. As you change one part or setting, it may require making changes in other settings in order to keep or find the proper balance of the different fuel circuits. This balancing concept also applies to the mid-range and wide-open-throttle operations.
  
 The Transfer Ports rely on the properly sized Slow Jet for the Transfer Fuel Mix, especially since there is no other adjustment available to control that mix. This is an important consideration because the Transfer Fuel Mix is not only active during the brief period of transition between idle and acceleration,​ but is also active during the much longer period of minimal speed cruising, where the throttle plate is mostly-closed. The Transfer Ports rely on the properly sized Slow Jet for the Transfer Fuel Mix, especially since there is no other adjustment available to control that mix. This is an important consideration because the Transfer Fuel Mix is not only active during the brief period of transition between idle and acceleration,​ but is also active during the much longer period of minimal speed cruising, where the throttle plate is mostly-closed.
Line 351: Line 386:
 Having gained access to the IMS, it is recommended that you start by opening the IMS from GENTLY seated to 2-1/2 turns CCW. This setting is likely to be larger than the factory setting, which is often in the 1 to 1-1/2 turns range. By opening the IMS more, we are richening the Idle Fuel Mix to provide addition fuel during idle & transfer operations.This may also help the engine run cooler. Having gained access to the IMS, it is recommended that you start by opening the IMS from GENTLY seated to 2-1/2 turns CCW. This setting is likely to be larger than the factory setting, which is often in the 1 to 1-1/2 turns range. By opening the IMS more, we are richening the Idle Fuel Mix to provide addition fuel during idle & transfer operations.This may also help the engine run cooler.
  
-**Thus far,** the throttle plate has been positioned between the Idle Port & the Transfer Ports, the Slow Jet has been chosen as stock or a 45 if the engine is 1200 or Stage One, the IMS cap was removed and the IMS was adjusted to 2-1/2 turns out from GENTLY seated. In addition, a selected needle was installed in the slide along with a reasonable choice for the Main Jet. These parts and settings were selected to provide a valid STARTING POINT for further, more accurate, adjustments.+**Thus far,** the throttle plate has been positioned ​(as much as possible) ​between the Idle Port & the Transfer Ports, the Slow Jet has been chosen as stock or a 45 if the engine is 1200 or Stage One, the IMS cap was removed and the IMS was adjusted to 2-1/2 turns out from GENTLY seated. In addition, a selected needle was installed in the slide along with a reasonable choice for the Main Jet. These parts and settings were selected to provide a valid STARTING POINT for further, more accurate, adjustments.
  
 While the proper idle rpm will be set AFTER adjusting the IMS setting (using the Idle Speed Screw), it is important to isolate the Idle Port operation from the Transfer Ports. While the proper idle rpm will be set AFTER adjusting the IMS setting (using the Idle Speed Screw), it is important to isolate the Idle Port operation from the Transfer Ports.
Line 358: Line 393:
  
  
-At this point, we need the engine to be warmed up to normal operating temperature to continue tuning the carb. A cold engine may operate quite differently once warmed up, therefore, tuning the carb while the engine is cold is not validSince we set the idle screw very low, you may need to use the throttle or enrichener ​to keep the bike running...+At this point, we need the engine to be warmed up to normal operating temperature to continue tuning the carb. A cold engine may operate quite differently once warmed up, therefore, tuning the carb while the engine is cold is not usually successful. 
 + 
 +Start the engine and use the enrichener ​(since the engine is cold) for the first 30-90 seconds, while you take the bike for a 10-15 minute ride to warm the engine fullyThen be careful of the burn potential while working around a hot engine and even hotter exhaustMake sure you have no intake leaks in the manifold seals by using an unlit propane torch to flow propane around all three manifold seals. The engine idle will alter if an intake leak allows propane into the manifold.
  
-Start the engine and use the enrichener for the first 1-3 minutes while you take the bike for a 10-15 minute ride to warm the engine fully. Then be careful of the burn potential while working around a hot engine. Make sure you have no intake leaks in the manifold seals by using an unlit propane torch to flow propane around those seals. The engine idle will alter if an intake leak allows propane into the manifold. 
  
 ==== The Idle Drop Method (IDM) ==== ==== The Idle Drop Method (IDM) ====
Line 366: Line 402:
 The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM. The Idle Drop Method (IDM) will help find the right setting for the Idle Mixture Screw (IMS)((see the chrishajer thread link below)). At idle, the engine will have difficulty if the idle fuel mix is too lean or if the idle fuel mix is too rich. There is a small range between those excesses, which is the point of this adjustment. This procedure does require the correct Slow Jet, so you may need to change the Slow Jet if you cannot find the described idle range while performing the IDM.
  
-With the engine ​idling, set the idle speed as low as the possible ​for smooth engine operation. Lock the idle speed with the throttle grip lock rather than changing the setting of the Idle Set Screw (which should still be between the Idle Port & the Transfer Ports).+If you have previously set the throttle plate, between the idle port and the transfer ports, using the Idle Set Screw, you may need to roll the throttle slightly (at the beginning of this process) to keep the engine ​idle. With the throttle grip, set the idle speed as low as possible, yet still smooth engine operation. Lock the idle speed with the throttle grip lock (rather than changing the setting of the Idle Set Screwwhich should still be (as close as possible) ​between the Idle Port & the Transfer Ports). 
 + 
 +Now carefully reach under the carb and adjust the IMS with very small increments, turning it counter-clockwise (as if looking up from below). This is enrichening the fuel mix. Listen for the engine speed to begin faltering, then STOP adjusting the screw. Now begin turning the IMS clockwise with very small movements. Listen for the engine speed to return to running well and then begin faltering as you continue to turn the screw clockwise, which will create a lean condition. When it falters, STOP adjusting the screw. 
 + 
 +Do this several times to be sure of your results and to calculate the amount of movment in 1/8 turn increments (1/2 of a 1/4 turn = 1/8 turn) that represents this range, from too rich to too lean. 
  
-Now carefully reach under the carb and adjust ​the IMS in very small incrementsturning it counter-clockwise (as if looking up from below)This is enrichening the fuel mixListen for the engine speed to begin falteringSTOP adjusting the screwNow begin turning ​the IMS clockwise in very small movements. Calculate ​the amount ​of movment in 1/8 turn increments ​(1/2 of a 1/4 turn = 1/8 turn)Listen for the engine speed to begin faltering due to a lean condition. STOP adjusting ​the screw.+| **Note - Trouble Finding A Change** - You may still have the throttle plate too far open, thereby running on the Transfer Ports instead of the Idle Port. But, if you have carefully set the throttle plate & still can't find a fall off until below 1/2 turn out, you need a smaller Slow JetIf you can't find a fall off in idle until beyond 3-1/2 turns out, you need a larger Slow Jet. However, it is not recommended to use a smaller size than 42 nor larger size than 46If the IMS setting appears ​to make no difference, you may have other issuesYou may have an intake leak or exhaust leakYou may have fuel leaking into the carb thru the vacuum hose because ​of a defective petcock diaphragm or thru a defective Accelerator Pump diaphragm.((oldboy at Post#7 - http://xlforum.net/forums/​showthread.php?​t=2076811)) Be sure to double check the throttle plate position |
  
-(Note: If you can't find a fall off until below 1/2 turn out, you need a smaller Slow Jet. If you can't find a fall off in idle until beyond 3-1/2 turns out, you need a larger Slow Jet.) 
  
-Now, use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well.+**Once you have found the range,** use the counting you made (of the number of 1/8 turns) in order to make a setting of the IMS in the near center of the range you moved the screw from TOO RICH to TOO LEAN. For instance, if after finding the TOO RICH (CCW) setting, you then counted turning the screw SIX 1/8 turns (going CW) when you found the TOO LEAN condition, you would NOW turn the screw back (CCW) THREE 1/8 turns in order for it to be in the center of the range that operated well. In fact, to be on the safe side of that setting, you  might want to go an extra 1/16 to 1/8 turn more rich.
  
 You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again. You can try this several times to assure yourself that you found the TOO RICH condition (CCW), then found the TOO LEAN condition (CW) and then were able to set the IMS (CCW) at the center between those. If the idle increases significantly during the adjustment, turn the throttle down to lower the RPMs and do the check again.
Line 378: Line 418:
 The goal is to have the engine properly idle from the Slow Jet & the Idle Mixture Screw rather than by opening the throttle plate with the Idle Set Screw or throttle grip. Once you are satisfied that you did find the proper setting, you can turn the bike off. The goal is to have the engine properly idle from the Slow Jet & the Idle Mixture Screw rather than by opening the throttle plate with the Idle Set Screw or throttle grip. Once you are satisfied that you did find the proper setting, you can turn the bike off.
  
-Now check to see how many turns you must go (clockwise) until you GENTLY seat (closed) the IMS. WRITE DOWN THIS SETTING. That's it - You completed the Idle Mixture Screw setting using the Idle Drop Method.+Now check to see how many turns you must go (clockwise) until you GENTLY seat (closed) the IMS. **__WRITE ​DOWN THIS SETTING.__** Now put the IMS back to where it belongs. That's it - You completed the Idle Mixture Screw setting using the Idle Drop Method.
  
-You can now release the throttle lock. Start the engine & adjust the Idle Set Screw (it should require very little adjustment) for the proper idle speed, typically, between 950 & 1050 RPMs.+You can now release the throttle lock. Start the engine & adjust the Idle Set Screw (it should require very little adjustment) for the proper idle speed, typically, ​it should be set between 950 & 1050 RPMs.
  
 If you blip the throttle a few times, the engine should respond crisply. If you roll the throttle open, it should respond smoothly, increasing the RPMs without hesitation. If you blip the throttle a few times, the engine should respond crisply. If you roll the throttle open, it should respond smoothly, increasing the RPMs without hesitation.
Line 399: Line 439:
 | When blipping the throttle, two things happen:\\ \\ 1. You are shooting some fuel in with the accelerator pump.\\ 2. When you blip the throttle, you are actually opening the throttle plate, and that larger opening causes a very [quick/​temporary] minor drop in velocity through the carb and reduces the signal (vacuum, pull) across the fuel jets, so you flow less fuel for an instant. The accelerator pump is supposed to compensate for that somewhat. The problem is, with a very short stroke of the accelerator pump rod, like a blip does, not much if any fuel is actually shot, so the pump is not doing its job, in some cases. | | When blipping the throttle, two things happen:\\ \\ 1. You are shooting some fuel in with the accelerator pump.\\ 2. When you blip the throttle, you are actually opening the throttle plate, and that larger opening causes a very [quick/​temporary] minor drop in velocity through the carb and reduces the signal (vacuum, pull) across the fuel jets, so you flow less fuel for an instant. The accelerator pump is supposed to compensate for that somewhat. The problem is, with a very short stroke of the accelerator pump rod, like a blip does, not much if any fuel is actually shot, so the pump is not doing its job, in some cases. |
  
-The second thing to say is that **YOU MUST** get a great tune from everything else before addressing the farts, because fixing other issues may eliminate or minimize the farts anyway. So, get your **timing** set correctly, get your **fuel flow** maximized and make certain you have no **air intake leaks.** Get your **throttle plate** set right (between idle & transfer ports), choose the right idle jet and use the Idle Drop Method to get the **Idle Mixture Screw** (IMS) set correctly. Make sure the bike is thoroughly warmed up before tuning. Each of these areas will need specific settings to match your engine build, whether stock, stage one, 1200 conversion, cams, etc. __BE SURE YOU READ ALL OF THE CARB TUNING INFORMATION IN THIS SECTION.__+The second thing to say is that **YOU MUST** get a great tune from everything else before addressing the farts, because fixing other issues may eliminate or minimize the farts anyway. So, get your **timing** set correctly, get your **fuel flow** maximized and make certain you have no **air intake leaks.** Get your **throttle plate** set right (as much as possible ​between idle & transfer ports), choose the right idle jet and use the Idle Drop Method to get the **Idle Mixture Screw** (IMS) set correctly. Make sure the bike is thoroughly warmed up before tuning. Each of these areas will need specific settings to match your engine build, whether stock, stage one, 1200/​1250/​1275 ​conversion, cams, etc. __BE SURE YOU READ ALL OF THE CARB TUNING INFORMATION IN THIS SECTION.__
  
 The third thing to say is that it should be obvious that to correct a lean condition we need to add fuel to the mix (unless an air leak is the cause of the lean condition). But we need to add fuel carefully to address this quick, temporary, lean condition without drowning the entire carb operating range in extra fuel. A typical response is to increase the idle jet, but if you increase the idle jet larger than a size 45 or 46 you are flooding too much fuel into the transfer ports and the overall mix. The third thing to say is that it should be obvious that to correct a lean condition we need to add fuel to the mix (unless an air leak is the cause of the lean condition). But we need to add fuel carefully to address this quick, temporary, lean condition without drowning the entire carb operating range in extra fuel. A typical response is to increase the idle jet, but if you increase the idle jet larger than a size 45 or 46 you are flooding too much fuel into the transfer ports and the overall mix.
Line 405: Line 445:
 **Some considerations:​** **Some considerations:​**
  
-A) Even when tuned correctly, cold engines are more likely to have carb farts than after they warm up. It is easier to create a lean condition when you open the throttle and gulp a large amount of cold air. If you ride off while the engine is still cold, expect to have farts. When the outside temperature is cold, you may also notice more carb farts for a longer period for the same reason. Trying to set your tune to eliminate carb farts that occur under cold conditions is likely to lead to excess fueling. ​Be sure to warm up the engine.+A) Even when tuned correctly, cold engines are more likely to have carb farts than after they warm up. It is easier to create a lean condition when you open the throttle and gulp a large amount of cold air. If you ride off while the engine is still cold, expect to have farts. When the outside temperature is cold, you may also notice more carb farts for a longer period for the same reason. Trying to set your tune to eliminate carb farts that occur under cold conditions is likely to lead to excess fueling. ​Instead, be sure to fully warm up the engine ​before tuning.
  
 B) You __should__ need the enrichener to start a cold engine. If you don't need it, your carb settings are too rich from the start. Go back to the general tuning stage and get this corrected before looking at carb farts. You may not have carb farts if you are that rich (which is not a good solution). B) You __should__ need the enrichener to start a cold engine. If you don't need it, your carb settings are too rich from the start. Go back to the general tuning stage and get this corrected before looking at carb farts. You may not have carb farts if you are that rich (which is not a good solution).
  
-C) HD added an Accelerator Pump on the CV40 in 1989 to help minimize carb farts by squirting extra fuel into the carb when you first twist the throttle. However, the EPA settings on the carb create a general lean condition which tends to increase the problem. This is another reason to do a proper tune on the carb, getting the overall Air-Fuel-Ratio (AFR) right, before addressing carb farts. Be sure the Accerator Pump is squirting a good spray into the carb, directed at the needle.+C) HD added an Accelerator Pump on the CV40 in 1989 to help minimize carb farts by squirting extra fuel into the carb when you first twist the throttle. However, the EPA settings on the carb create a general lean condition which tends to increase the problem. This is another reason to do a proper tune on the carb, getting the overall Air-Fuel-Ratio (AFR) right, before addressing carb farts. Be sure the Accerator Pump is squirting a good spray into the carb, directed at the needle ​to break up the stream into a spray.
  
 Every carb and engine is slightly different. Pay close attention to when & how you are getting carb farts. Use a thorough and patient approach to finding where the problem is located and choosing the right solution. Every carb and engine is slightly different. Pay close attention to when & how you are getting carb farts. Use a thorough and patient approach to finding where the problem is located and choosing the right solution.
Line 484: Line 524:
 The Accelerator Pump (AP) is part of the Transfer function of the carburetor, providing additional fuel when the carb transitions from the Idle operation up to the acceleration and/or cruising operation. The Accelerator Pump (AP) is part of the Transfer function of the carburetor, providing additional fuel when the carb transitions from the Idle operation up to the acceleration and/or cruising operation.
  
-The AP is attached to the Float Bowl. The pump utilizes a diaphragm bladder & spring that is operated by a rod connected to the throttle cam on the side of the carb. When the throttle is quickly opened, the Idle & Transfer ports are too small to supply enough fuel to keep the carb from starving. To prevent this lean condition, the AP sends fuel thru a supply channel in the bowl body up thru a protruding tube into the venturi. This sprays additional fuel out of its nozzle into the carb air flow to help richen the mixture during the transition off idle (or whenever the throttle is closed & reopened).+The pump is attached to the Float Bowl. It utilizes a diaphragm bladder & spring that is operated by a rod connected to the throttle cam on the side of the carb. When the throttle is quickly opened, the Idle & Transfer ports are too small to supply enough fuel to keep the carb from starving. To prevent this lean condition, the Accelerator Pump sends fuel thru a supply channel in the bowl body up thru a protruding tube into the venturi. This sprays additional fuel out of its nozzle into the carb air flow to help richen the mixture during the transition off idle (or whenever the throttle is closed & reopened).
  
-There is a check valve utilized to keep the fuel from being pulled from the nozzle tube when the pump rod is released and the AP cavity expands, creating a vacuum. In the 2003-earlier models, the check valve is in the nozzle tube (sold as part of the float bowl). When the AP rod is released, the pump sucks more fuel from the bowl (through a bleed hole in the supply channel) to refill its reservoir and is ready for another transition event.+There is a check valve utilized to keep the fuel from being pulled from the nozzle tube when the pump rod is released and the AP cavity expands, creating a vacuum. In the 2003-earlier models, the check valve is in the nozzle tube (sold as part of the float bowl). When the pump rod is released, the pump sucks more fuel from the bowl (through a bleed hole in the supply channel) to refill its reservoir and is ready for another transition event.
  
-In the 2004-2006 models, the check valve was moved to the AP body. This required a separate hole in the bowl to allow fuel into the check valve and then to the pump. When the pump rod is activated, the pump output pushes fuel thru the fuel supply channel as it travels to the nozzle tube. A small bleed hole is still utilized in the supply channel but is no longer used to refill the AP reservoir.+In the 2004-2006 models, the check valve was moved to the pump body. This required a separate hole in the bowl to allow fuel into the check valve and then to the pump. When the pump rod is activated, the pump output pushes fuel thru the fuel supply channel as it travels to the nozzle tube. A small bleed hole is still utilized in the supply channel but is no longer used to refill the AP reservoir.
  
  
Line 505: Line 545:
 {{:​techtalk:​evo:​carb:​xl1200s_keihin_cv_float_bowl_-_49_state_by_hippysmack.jpg?​direct&​300|}} ((photo by Hippysmack)) \\ {{:​techtalk:​evo:​carb:​xl1200s_keihin_cv_float_bowl_-_49_state_by_hippysmack.jpg?​direct&​300|}} ((photo by Hippysmack)) \\
  
-There are 3 types checks for the accel pump jets: ball, needle and calibrated orifice-(no check at all). ((buster of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2024981)) ​\\ +There are 3 types of flow checks ​(on different versions of the CV40) for the accelerator ​pump jets: ball, needle and calibrated orifice-(no check at all). ((buster of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2024981))((Older units had change-able jets to calibrate the squirt, newer ones are fixed and can only adjust the timing of the squirt.)) \\
-Older units had change-able jets to calibrate the squirt, newer ones are fixed and can only adjust the timing of the squirt. \\+
  
 {{techtalk:​evo:​carb:​cv40-accelpump-ckvalve.jpg |Annotated by IXL2Relax at the XLForum}} {{techtalk:​evo:​carb:​cv40-accelpump-ckvalve.jpg |Annotated by IXL2Relax at the XLForum}}
Line 514: Line 553:
 {{:​techtalk:​evo:​carb:​91_keihin_cv_accelerator_pump_jet_by_blackbikedave.jpg?​direct&​400|}} ((photos by BlackBikeDave,​ cropped-annotated by Hippysmack http://​xlforum.net/​forums/​showthread.php?​t=2024981)) \\ {{:​techtalk:​evo:​carb:​91_keihin_cv_accelerator_pump_jet_by_blackbikedave.jpg?​direct&​400|}} ((photos by BlackBikeDave,​ cropped-annotated by Hippysmack http://​xlforum.net/​forums/​showthread.php?​t=2024981)) \\
  
-**Float Bowl Overflow** - Notice the Overflow Tube in the above picture. The channel for the escape of that float bowl overflow was also used for a float bowl drain. ​This is shown at the beginning of this page on the picture of the bottom of the float bowl. This overflow was a safeguard against the failure of the float bowl valve from not closing. Should that happen, the fuel would be expelled onto the ground rather than being pushed into the intake manifold and filling the cylinders (and eventually the crankcase) with raw fuel.+**Fuel Float Hinge Pin - CAUTION!** - Be very careful removing the hinge pin on which the fuel float operates. The pin should ONLY be REMOVED in one direction - the direction as shown by an arrow embossed in the carb body. To REINSERT the pin, press it into place in the opposite direction from the embossed arrow. Be careful not to stress or break the mounting posts nor twist & damage the float arms. 
 + 
 +**Float Bowl Overflow** - Notice the Overflow Tube on the bottom of the float bowl, in the [[techtalk:​evo:​carb02#​working_with_cv40_carburetors|above picture]]. The channel ​used for the escaping ​overflow ​fuel was also used for a float bowl drain. ​The overflow was a safeguard against the failure of the float bowl valve from not closing. Should that happen, the fuel would be expelled onto the ground rather than being pushed into the intake manifold and filling the cylinders (and eventually the crankcase) with raw fuel.
  
 Note, however, that the 1998-2003 1200S carbs have no float bowl overflow tube protection. They also have no drain plug & hose to empty float chamber for off riding season or extended storage. Note, however, that the 1998-2003 1200S carbs have no float bowl overflow tube protection. They also have no drain plug & hose to empty float chamber for off riding season or extended storage.
Line 546: Line 587:
 {{:​techtalk:​evo:​carb:​cv40-enrichener-assy.jpg|}}((Pics from Phillober t=848307\\ & gm1ll t=1553245))((Annotated by IXL2Relax at the XLForum)) {{:​techtalk:​evo:​carb:​cv40-enrichener-assy.jpg|}}((Pics from Phillober t=848307\\ & gm1ll t=1553245))((Annotated by IXL2Relax at the XLForum))
  
-An XLForum Thread ​showing ​the replacement of the cable is here: http://​xlforum.net/​forums/​showthread.php?​t=848307+An XLForum Thread ​discussing ​the replacement of the cable is here (but pics are missing): http://​xlforum.net/​forums/​showthread.php?​t=848307
  
 \\ \\
Line 557: Line 598:
 Reversion is created in the engine combustion cycle by the relationship between the cams and the exhaust system. Specifically,​ between the harmonic waves created in the exhaust pipes and the overlap of the exhaust valve about to close while the intake valve is already opening. This overlap period, where both valves are open at the same time, is usually extended in high lift cams, causing the exhaust system to have a great affect on the cylinder fill operation. The exhaust functioning can have a positive or negative affect. Reversion is created in the engine combustion cycle by the relationship between the cams and the exhaust system. Specifically,​ between the harmonic waves created in the exhaust pipes and the overlap of the exhaust valve about to close while the intake valve is already opening. This overlap period, where both valves are open at the same time, is usually extended in high lift cams, causing the exhaust system to have a great affect on the cylinder fill operation. The exhaust functioning can have a positive or negative affect.
  
-If/when reversion is occuring, the intake charge ends up passing through the carb three times: pulled in, pushed out, and pulled back in again. Each time it is picking up fuel making the mixture richer. ((Based on info from Aaron Wilson from the XLForum (aswracing) - http://​xlforum.net/​vbportal/​forums/​showthread.php?​t=1028905 - Post#12))+If/when reversion is occuring, the intake charge ends up passing through the carb three times: pulled in, pushed out, and pulled back in again. Each time it is picking up fuel making the mixture richer. ((Based on info from Aaron Wilson from the XLForum (aswracing) - http://​xlforum.net/​vbportal/​forums/​showthread.php?​t=1028905 - Post#15))
  
 You can read more in the REF Section on [[techtalk:​evo:​carb04#​exhaust_pipes_cams_-_power_or_reversion|Exhaust Pipes & Cams - Power or Reversion.]] ​ You can read more in the REF Section on [[techtalk:​evo:​carb04#​exhaust_pipes_cams_-_power_or_reversion|Exhaust Pipes & Cams - Power or Reversion.]] ​