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techtalk:evo:carb02 [2020/01/12 20:04]
ixl2relax [The Idle/Transfer Ports Operation & Tuning]
techtalk:evo:carb02 [2020/07/23 21:25] (current)
ixl2relax [Accelerator Pump and Fuel Float Bowl]
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 This is from an [[http://​xlforum.net/​forums/​showthread.php?​t=30748|XLForum thread]]: chrishajer wrote - CBAS5 and I were talking about what it should sound like, good, and we filmed that one. Then he said "you know, we should show a bad one too" so we did that. I think the [vacuum] sound and the speed that the slide comes down are the two most important things. Those things you can't describe to someone really. I can't anyway. But it's absolutely the best way to verify that the diaphragm is seated properly. This is from an [[http://​xlforum.net/​forums/​showthread.php?​t=30748|XLForum thread]]: chrishajer wrote - CBAS5 and I were talking about what it should sound like, good, and we filmed that one. Then he said "you know, we should show a bad one too" so we did that. I think the [vacuum] sound and the speed that the slide comes down are the two most important things. Those things you can't describe to someone really. I can't anyway. But it's absolutely the best way to verify that the diaphragm is seated properly.
  
 +
 +** Youtube Videos of:\\
 <font 16px/Arial, , ;;#​ffffff;;#​00FFF0>​ <font 16px/Arial, , ;;#​ffffff;;#​00FFF0>​
-[[http://​www.youtube.com/​watch?​v=L4knwjlNC1o|YouTube Video of GOOD working slide]]</​font>​ .........+[[http://​www.youtube.com/​watch?​v=L4knwjlNC1o|The Sound of GOOD working slide]]</​font>​ .........
 <font 16px/Arial, , ;;#​ffffff;;#​FFFF00>​ <font 16px/Arial, , ;;#​ffffff;;#​FFFF00>​
-[[http://​www.youtube.com/​watch?​v=k1YOkoekIeA|YouTube Video of MALFUNCTIONING slide]]</​font>​\\+[[http://​www.youtube.com/​watch?​v=k1YOkoekIeA|The Sound of MALFUNCTIONING slide]]</​font>​**
  
  
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 {{  :​techtalk:​evo:​carb:​cv40-needle-em-jets.jpg?​360| Photo by IXL2Relax at the XLForum}} {{  :​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))
 +
 +More info & links here: [[:​techtalk:​evo:​carb02c|SubDoc - Why Not Dynojet Kits?]]
  
 **__To check for DynoJet parts, look at these 4 things:__** ((Identify DJ vs Keihin - http://​xlforum.net/​forums/​showpost.php?​p=5238545)) **__To check for DynoJet parts, look at these 4 things:__** ((Identify DJ vs Keihin - http://​xlforum.net/​forums/​showpost.php?​p=5238545))
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   * 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}} {{  :​techtalk:​evo:​carb:​cv40-needle-jet.jpg?​200| Annotated by IXL2Relax at the XLForum}}
-  * 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+  * 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
  
 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'​.
  
-More info & links here: [[:​techtalk:​evo:​carb02c|SubDoc - Why Not Dynojet Kits?]]+\\
  
 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))
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   * Check IMS seat (Has the screw needle tip deformed the hole?)   * Check IMS seat (Has the screw needle tip deformed the hole?)
   * Set initial IMS to 2-1/2 turns out from lite seat   * Set initial IMS to 2-1/2 turns out from lite seat
 +
 +==== Inspecting Float Level - 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.
 +  * 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 tube to the same level as that in the bowl itself.
 +  * A carburetor with a properly adjusted float level will have the level the same height as the float bowl 0-ring surface.
  
 \\ \\
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-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 valid. Since 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 valid.
  
-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.+Start the engine and use the enrichener ​if the engine is cold, for the first minute or so, 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) ====
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 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 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 between the Idle Port & the Transfer Ports).
  
-Now carefully reach under the carb and adjust the IMS in 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 falteringSTOP adjusting the screw. Now 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.+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.
  
-(Note: If you can't find a fall off until below 1/2 turn out, you need smaller Slow Jet. If you can't find a fall off in idle until beyond 3-1/2 turns outyou need a larger Slow Jet.)+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 rangefrom too rich to too lean.
  
-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.+ 
 +| **Note - Trouble Finding A Change** - If you can't find a fall off until below 1/2 turn outyou 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. If the IMS setting appears to make no difference, you may have other issues. You may have an intake leak or exhaust leak. You 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)) Or, you may have the throttle plate too far open, thereby running on the Transfer Ports instead of the Idle Port. | 
 + 
 + 
 +**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.
  
 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.
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 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.
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 | 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 (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.
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 **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.
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 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.
  
  
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 {{:​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}}
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 {{:​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** - Be very careful removing the hinge pin on which the fuel float operates. The pin is to ONLY be inserted in one direction. That direction is shown by an arrow embossed in the carb body. To remove the pin, press it out 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.