Friday, July 10, 2009

Lean/Rich Carburetor Adjustments

From the best threads at : http://www.vtxcafe.com

So for the past week I have been reading dozens of threads and pages of posts. I have found tons of great pieces of advice that have worked for members, but nothing seemed to be located in one thread (you have to read...sometimes...10-20 pages before you come to an answer). PLEASE CHECK END OF THREAD FOR CURRENT SYMPTOMS/SOLUTIONSWhen members post new/edited or other symptoms/solutions, I'll add to this this thread quote and continue what has been started to prevent reading all the postings.This is what I have gathered thus far (please correct any mistakes I make because I know that I will make them) and these are by far "typical" symptoms from users:Is my bike LEAN?
Very white plugs
Popping/backfiring from exhaust on deceleration
Bike wants to die or almost dies in slow maneuvers
Blip on the throttle causes the engine speed to hang slightly before recovering
Excess fuel in Airbox (from Carburetor spitting fuel to compensate for lack there of)
Hesitation or stuttering while starting from a stop in the low rpm range (goes away when higher rpm's are achieved) Is my bike RICH?
Black/oily plugs (also caused from the dreaded Choke)
Bike hesitates when heavy throttle is applied or is slow to "speed up" (not to be confused with the 1/8-1/4 throttle turn while your bike is at a stop...the A/F screw affects the 1/8-1/4 turn while the needle/shim affects the mid to higher range)
Blip on throttle causes the engine speed to drop below idle and then it recovers
Significant gas odor while riding Solutions for LEAN:
Turn out (counterclockwise) A/F screw (start with 1/8 turn increments)
Add shim(s) to the needle Solutions for RICH:
Turn in (clockwise) A/F screw (start with 1/8 turn increments)
If shim(s) exist, try removing them if A/F screw did fix the problem Idle Speed:
900rpm +/- 100rpm
May need to be set slightly higher for colder temps Shimming Heights (per SCAR):
"Open" style airbox and after market "free flow" pipes... usually about 2or 3 shims.
Airbox flowing more air than stock design, but not in the "heavy breathing" class and/or pipes either free flow or somewhat restricted... usually about 1or 2 shims
Stock airbox (K&N filter in stock box is still "stock") and after market pipes... usually 0 or 1 shims
Stock airbox and stock pipes...tune the A/F screw for maximum performance. Shimming note (per Charlie D):
Clip positions on after market are the same as shimming up or down ( a shim for half clip position). Helpful Links:Link to help understand the workings of Carburetor. http://www.factorypro.com/tech_tunin...m_engines.htmlHere's another good read, talks about jetting, needle shimming and plug chops ect: http://crapmods.com/phpBB/viewtopic.php?t=3604

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