Topic: 350F Carb Tuning

[sfhurst]

I installed a rebuild kit on each carb.  I manually adjusted the throttle plates before mounting.  I vacuum balanced the carbs.  There is no binding of the throttle cable.  The engine starts easily.  Nevertheless, I have the following problems.

Even after being warmed up the RPM fluctuates at idle. 

The engine responds immediately to input from the throttle but will not return to idle when the throttle is released.  The control linkage immediately returns to the idle position when the throttle is release, but the RPM does not drop, or drops very slowly.

Any suggestions will be greatly appreciated.

[newday777]

How/in what way, did you clean the carbs?
Did you clean the original brass or put in aftermarket brass parts?
Did you test for vacuum leaks around the intake to the head? How did you test? This is critical and the mist likely cause of your surging.
Are you running the stock air filter or pods?

[newday777]

BTW, you should have continued with this on your 350F Surging thread rather than starting this new thread.
http://forums.sohc4.net/index.php/topic,193493.msg2258930.html#msg2258930
I just looked through some of your posts(just click on your screen name so you can find your posts)and your replies are short and little information given by you as to how you went about checking for vacuum leaks. Asking for help also includes you replying back with full information as to what and how you have done and the results you got. We are here to try to help, but without you replying back until good results happen, forums won't work for anyone. We don't know what your capabilities are or how you do the work you've done without your input. These carbs are intricate and need to be rebuilt properly.

Did you remove the the intake bungs from the head and put in new O-rings(#9 in the fiche)? If not you probably have leakage there.

[sfhurst]

Thanks for the replies.  I replaced the internal brass pieces with new after-market pieces from the rebuild kit.  Running stock air filter and original airbox.  I blew out all of the internal passages with pressurized carb cleaner.  I did remove the intake manifolds from the head and replace the O rings.  I did not conduct a vacuum test (don't know how to do that) because I thought the new O rings would have sealed that connection.

I believe I have all of the mechanical skills and tools required, but this is my first multi-carb motorcycle restoration.  I obviously still have a lot to learn.

[Bodi]

"I replaced the internal brass pieces with new after-market pieces from the rebuild kit."
This is usually a mistake. They are not equal to Keihin parts.

[sfhurst]

I get aftermarket does not equal OEM.  I pulled the airbox and carbs (I'm getting pretty good at that), replaced the manifold O rings and reinstalled everything.  Success, or at least MUCH better idle and throttle response.  Thanks for everyone's help.  I now have a timing question, which is continuation of a previous post.