Differences

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

--- techtalk:evo:carb02 [2019/11/10 03:38]
ixl2relax [Enrichener Function (Choke)]
+++ techtalk:evo:carb02 [2020/01/22 05:46]
ixl2relax [Why Not Dynojet Kits?]
@@ Line 100: / Line 100: @@
 {{  :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))
+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))
@@ Line 114: / Line 116: @@
 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))
-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))
@@ Line 309: / Line 311: @@
 **Main Jet** - The Main Jet itself does not begin to limit fuel delivery to the carb operation until the vacuum slide is 75-90% wide open and the engine is revving. Until then, other parts & factors (such as the idle mixture screw, slow-jet and needle position in the needle jet) are controlling the fuel utilized by the carb.
-**Needle & Needle Jet** - The needle is a tapered, nail-like, rod that operates from the bottom of the slide into the needle jet. It does not affect the flow of fuel until the throttle plate opens sufficiently to create an active vacuum in the outer section of the venturi, which will lift the slide and move the needle in the needle jet. The fuel mix supplied thru the needle jet, by your selected needle and the emulsion tube, will combine with the transfer fuel mix of the slow jet as the carb operation moves out of the transfer period into the mid-range of the throttle/slide function.\\ The main jet, located at the bottom of the emulsion tube, is way below where the needle rides and has no relationship with what the needle does other than to create an eventual upper fuel limit at WOT. ((wedge of the XLFORUM http://xlforum.net/forums/showthread.php?t=1820463&page=9)) The needle rides in the needle jet which is the silver jet (hollow cylinder) that sticks up from the bottom of the throat of the carb and the needle moves up and down thru it during operation.\\ The tapered needle and needle jet together control fuel flow coming out of the emulsion tube into the throat. After the needle is almost up and out of the needle jet, then the main jet will become the limiting factor for the fuel flow at the wide open throttle position (WOT). Until the needle gets out of the way, the main jet is doing nothing to limit the needed fuel.\\ ( See this [[http://xlforum.net/forums/showthread.php?t=165259|XLForum Thread]] on needle dimensions)
+**Needle & Needle Jet** - The needle is a tapered, nail-like, rod that operates from the bottom of the slide into the needle jet. It does not affect the flow of fuel until the throttle plate opens sufficiently to create an active vacuum in the outer section of the venturi, which will lift the slide and move the needle in the needle jet. The fuel mix supplied thru the needle jet, by your selected needle and the emulsion tube, will combine with the transfer fuel mix of the slow jet as the carb operation moves out of the transfer period into the mid-range of the throttle/slide function.
+The main jet, located at the bottom of the emulsion tube, is way below where the needle rides and has no relationship with what the needle does other than to create an eventual upper fuel limit at WOT. ((wedge of the XLFORUM http://xlforum.net/forums/showthread.php?t=1820463&page=9)) The needle rides in the needle jet which is the silver jet (hollow cylinder) that sticks up from the bottom of the throat of the carb and the needle moves up and down thru it during operation.
+The tapered needle and needle jet together control fuel flow coming out of the emulsion tube into the throat. After the needle is almost up and out of the needle jet, then the main jet will become the limiting factor for the fuel flow at the wide open throttle position (WOT). Until the needle gets out of the way, the main jet is doing nothing to limit the needed fuel.
+( 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.
-**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. (If by chance, for any reason, you have the throttle plate completely off, be aware that there is 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.)
+**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.
+(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|}}

Trace:

Differences

Navigation

Search

Toolbox