CB500K1 Hanging idle

[exelbyt]

Hello All, 

I once again need you help and guidance!

I am experiencing a hanging idle at 3000rpm.  When warm the engine hangs at 3000 if rev'd, or rises on its own once hot to hang at 3000.  I have been searching through different configurations but am yet to be successful.  Once rolling she rides well with lots of power but at idle and slow speeds hangs at 3000.

Current setup;
Open exhaust
Air pods (i understand this is a big part of the issue but they are staying)

Keihin carbs; 130 main jet, 42 slow jet, needle clip 4(one up from bottom)

I have tested using the air screw - 0, 1/4, 1/2, 3/4, 1, 1 1/4, 1 1/2, 1 3/4 and 2 turns out.  It seems to run best at 1 turn out but still hangs with all turns.

The plugs after idle are normal - not sooty.  They is no smoke coming from the exhaust but i do think that it may still be running lean at idle hence the hang.

You thoughts would be welcome!

Tom


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[Johnwebley]

air leak when hot,

 could be the carb to inlet rubbers,and/or the "O" rings between the manifolds and head,

  how old are the inlet rubbers?

 

[exelbyt]

Not sure how old they are but ive had them off and inspected them and they seem in good nick.  I have also checked with wd40 while running and the revs still stick.

I have also checked the throttle cables and understand its not the idle screw.


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[Nurse Julie]

That's the problem i had with my CB400/4. To cut a very long story short, I had resisted plug caps and I  fitted resisted plugs in error. Once I had changed the plugs for non resisted, problem solved immediately. Now, I wouldn't expect anyone else to do such a silly thing as I did but thought I would just mention it. In my defence D Sliver advertises the resisted plugs as the correct ones.....WRONG!!!

[exelbyt]

Carbs haven't been dismantled by me fully only cleaned as a bank.

The head gasket is leaking oil.  Could this be effecting the situation or is it likely to not contribute.  I am thinking it may be best to rebuild the head first and then work backwards.

Thoughts?


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[JamesH]

I'm assuming you've carefully synced the carbs?

Do as hairy says and remove the throttle cables completely and run the bike from a slave tank so you have full access to the carbs.
You can then eliminate then throttle cable setup as a cause of the hanging idle. Then report back...