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Discussion Starter · #1 ·
Hello Everyone,

I am new to this site and have been using it as a valuable resource while I rebuild my motorcycle. So let me dive right in. I bought a 1973 Honda CB350 Twin and after the rebuild I am having some idling issues. I calibrated the intake and exhaust valves, timed the motor and ignition, and gapped the spark plugs. I also synced the carbs and throttle cables.


Issues:
The motorcycle will idle between 2000-3000 rpms. If I apply the choke, the engine idle increases. The right tailpipe is hotter than the other. I was able to run the bike with only one spark plug at a time (so i know the spark plug is working in both cylinders). Has anyone had similar issues? I am currently scratching my head at this one.

Thank you.
 

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If everything is adjusted properly it is normal for the idle speed to increase as the choke is closed, at least up until the point that the choke makes it too rich to keep running. Unless the idle adjustment screws or the throttle cables are preventing the throttle plates from closing, I'd be checking for vacuum leaks.
 

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Richen up the idle mixture and adjust the throttle plates down. Sounds like the throttle is open so far, at idle, that the carbs are trying to run on the main circuit.
 

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If the left tailpipe isn’t hot, I don’t think you’re firing at all on the left cylinder. Just to clarify, you can run the bike for several minutes and comfortably grab the left header? Your points may be shorting or faulty, or a bad plug wire.
 

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Lots of threads on this site about "thoroughly" cleaned carbs. Sounds like the passages in the carb are still clogged. Carb cleaner will not flow through a completely blocked passage.
 

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Discussion Starter · #10 ·
Update....I was idling the motorcycle and realized that there is a vacuum leak in the intake manifold. I sprayed carb cleaner near the manifold and the RMPs shot right up. I will be ordering manifolds for both sides. Could i vacuum leak at the manifold be a result of the issues that i was having? Also, what is the chain size for a 1973 honda cb350, 530x96?
 
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