EVO strumbles off idle
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From: Indiana
EVO stumbles off idle
Purchased a 2000 FXR4 in May, 2010. Stock motor, Dyna2000p ignition, V&H drag pipes w/baffles, Doherty Power-Pacc A/C. Developed a rocker box leak so in the process of removing the rocker covers, I decided to replace the cam with a VT-3010. Used James Genuine Gaskets throughout.
While I had the carb off I decided to clean and rebuild it. Found out the original owner put a DynaJet kit in it. The rubber diaphragm had been pinched in the cover and had a tear in it. Replaced with a new one. Also replaced the emulsion tube with stock, inserted 185 main, 46 pilot jet, and needle.
Bike starts fine, idles nicely at 1000 RPM. HOWEVER, if I twist the throttle gently, trying not to engage the accelerator pump, the bike stumbles badly until it dies. I can keep it running as long as I rapidly twist the throttle, spraying gas from the accelerator pump.
I replaced the main with a 180, 175, 165, changed the pilot with a 45, changed spring and needle with another I had lying around. The bike idles good with all these changes, but as soon as it comes off idle it stumbles and dies. I took the carb off the bike and verified all was clean and everything correctly in place. Also checked the fuel height in the bowl by using a clear drain tube, taping it up the side of the carb and opened the drain screw. The fuel height was right on the top of the bottom bowl.
I am going to check the timing tonight and also check the operation of the VOES switch. Can anyone else recommend anything else to check? Thanks in advance.
--
Kevin
While I had the carb off I decided to clean and rebuild it. Found out the original owner put a DynaJet kit in it. The rubber diaphragm had been pinched in the cover and had a tear in it. Replaced with a new one. Also replaced the emulsion tube with stock, inserted 185 main, 46 pilot jet, and needle.
Bike starts fine, idles nicely at 1000 RPM. HOWEVER, if I twist the throttle gently, trying not to engage the accelerator pump, the bike stumbles badly until it dies. I can keep it running as long as I rapidly twist the throttle, spraying gas from the accelerator pump.
I replaced the main with a 180, 175, 165, changed the pilot with a 45, changed spring and needle with another I had lying around. The bike idles good with all these changes, but as soon as it comes off idle it stumbles and dies. I took the carb off the bike and verified all was clean and everything correctly in place. Also checked the fuel height in the bowl by using a clear drain tube, taping it up the side of the carb and opened the drain screw. The fuel height was right on the top of the bottom bowl.
I am going to check the timing tonight and also check the operation of the VOES switch. Can anyone else recommend anything else to check? Thanks in advance.
--
Kevin
Last edited by kemiha; Sep 22, 2010 at 11:56 AM. Reason: Added information
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
When you take a CV carb apart there is a little silver piece called the "needle Jet". It is radiused on the inside on the end that goes up and the needle goes in. the other end is square and goes down against the brass needle jet holder. Look closely at it as the radius is not very much. If this is installed with the radius down, square end up, you will get the symptoms you describe. Also a defective diaphragm/ diaphragm seal will cuase a similar problem. Hope this helps. P.S. Make sure your enrichner is fully seated.
Last edited by miacycles; Sep 22, 2010 at 07:11 PM.
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From: Indiana
Thanks miacycles, that was the issue. I turnd the needle jet over, placing the cupped end into the carb throat, and it runs well now. I wonder how many people have done this bonehead mistake like me 
. Thanks again!
. Thanks again!
Elite HDF Member
Joined: Sep 2007
Posts: 4,468
Likes: 12
From: Bluffton, South Carolina
Quite a few, including me many, many years ago!!! It's one of those mistakes you only make once !!! Glad to be of help.
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