black sooty plug

Ok im at my witts end here...ive tryed 2 carbs original 12mm with original jet...new carb 17.5 with 80 jet 90 i fid start at 100 & worked my way down.Ive tryed original air filter open air filter no filter nothings working...bike is idling fine & not bad upto half throttle even 3 quarter throttle..tried going down a plug as mechanic said the 8 wasn't burning fuel quick enough i have no air leaks,c,mon someone what can i try next tegards david...

 

A black sooty plug would suggest it's running too rich, vacuum tap leaking into the carb?

 

Hi & many many thanks for your reply I will have a go at looking into that cheers

 

Marsh i cannot thank you enough your right the vacuum tap most have bern loos because when i went to vheck it,it fell into the tank,bike is now running much better although i still dont know for sure on full throttle, can i use the sooty plugs again as i hsve no spares & best way to clean them up......thankyou.....

 

Give them a wire brushing and they'll be fine.

 

You need a blast cleaner to clean effectively, any problem fouling will be inside the threaded metal shell where a brush won't reach. As long as it runs and the carb is set up correctly the plug will clean itself when it gets hot enough...