Revs staying high...

[gavba]

Having trouble with rev's on my CB125 staying high for about 5-10 seconds after opening and closing the throttle. The left side spark plug seems to be a 'good' colour but the right side one is black and sooty. Also, it doesn't matter how much I adjust the carb on the right side, the plug either comes out dry or black and sooty.

I've checked and cleaned both carbs (polished the seats, checked float height, cleaned jets, made sure float needles are returning etc..) and have replaced the old jets on the right side carb with new ones (the correct sizes). The choke is operating as it should be.

I'm going to check tomorrow more thoroughly for air leaks but I haven't found any so far. I have used a mirror to make sure the throttle is actually operating correctly when inside the carb and it seems to be rising and returning fine.

I have recently replaced the exhaust and there seems to be a slight leak at the cylinder head gasket on the right hand side (the side with the fouled plug). Could this have anything to do with it?

I'm not sure what else to look for, unless it's an air leak as the carbs seem fine. Could this be an engine problem of some kind? Sticking valves or something like that?

Any suggestions would be appreciated as I'm almost out of ideas myself.

Cheers!

[bensmith]

Sticking valves? Looks like the mixture isnt quite right either. Replace air filter see if it helps.

[gavba]

It just seems like something is sticking and letting too much fuel/air in when the throttle is opened. Although if the valves were sticking I'd presume there would be no combustion at all.

The air filter seems fine, the trouble seems to persist with or without it.

I'll thoroughly check for air leaks and check the throttle operation again tomorrow.

[bensmith]

Sticking valves does seem like the culprit, could maybe be a vacuum leak. Clutch slipping, throttle cable might be getting stuck.

[DRZ4Hunned]

Sounds like a sticky throttle cable to me.
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