Question81 yamaha 400 special 11
I have cleaned and cleaned the carbs, I have traced my idle problem back to the carbs. Valves good ignition good. I have taken the caps off now on the idle airmixture screws and still cant get my left cylinder to fire consistantly to idle right. I beleive the mix in left cylinder is to lean because I can mist gasoline in the left aircleaner and it will fire correctly. After 1200 rpms the both cylinders fire fine all the way through the upper rpm range. It is just at 1200 rpm "idle" the left cylinder is not getting the proper fuel mix. I heard I may be able to move my slide needle to adjust the mix but will this affect my idle or just mid and upper rpm range. Please help direct me on this if you will. Thanks
Fred
Answerhttp://www.powersportspro.com/partsfish/login.asp to find more illustrations about your bike.
Be sure that your float levels are both correct.
Check idle jets for any restrictions. The holes are very tiny and the crossdrilled passages must be clear.
Check intake manifold for leaking gasket or the manifold for cracks, leading to air leaks.
Weak sparks can cause misfiring. Be sure that the spark plug caps are both around 3-5K ohms and not cracked or showing track marks inside.
Verify that the ignition timing is correct on both sides. Any variances will cause different vacuum signals to the metering circuits.
Yes, raising the needle with a small washer can help off idle response, but at closed throttle the idle circuits are doing most all the work. Raising the needle will affect 1/4 throttle up to 3/4 throttle settings. Synchronize the carbs with a vacuum gauge set or at least eyeball the throttle shafts to see that both are set to open at the same time and amount. Be sure that you have a snug fit on the vacuum port plug fittings on the intake manifolds. Check for excessive shaft play at the throttle butterflies, where you could get an air leak.
Is the compression the same on both sides?
Make sure that all mechanical/electrical issues are resolved, before you tackle final carb idle settings.
Bill "MrHonda" Silver
