The most common reason for the fuel combustion system to cause carbon build-up on the spark plug is a failed mixture of fuel and oxygen.Thanks for the advice so far. So with an intake leak I should be lean But my plugs say I'm running rich.If the spark plug is fouling because of a carbon build-up, the reason is likely due to the combustion system of the lawn mowerвЂ™s engine. Also have a poping coming from the rear cylinder exhaust. Also my plugs are carbon fouled I pulled them, cleaned them, put them back in, then let it idle for about 20 minutes pulled the plugs again and they're covered in black carbon.

Sorry about the detail-trying to eliminate every possibility. The garage put it back together and again I can't think of any way that should affect the ignition. The only recent change to the bike was a) changing the oil using car oil which wouldn't really affect the ignition even if it caused other problems (the fouling is dry sooty carbon not sticky oil) I also b) accidentally removed a bolt on the engine that held parts of the kickstart assembly. Should I adjust the carburettor next to make the feed leaner? I haven't done this before and I don't know if it's necessary normally? I don't think the battery power is a problem as the lights and electric start work normally (the electric start did fail a few months ago, but after I kick started it the electrics worked normally since then). I cleaned the air filter but it wasn't really dirty and might not be the cause of the problem. I notice a bit of sputtering when I use more revs, but not every time.

Keep engine operating temperature around 180 degrees.The adapter harness is designed to plug straight into the stock JZX100 harness. You should have 10-12 degree initial timing with 36-38 degrees total by 2,500 rpm. Check your distributor advance curve. Here are some things to do to solve that: Keep idle speed around 880-900 rpm in drive.

Thanks to you all I might be getting good at this stuff!The last post was made 10 years, 60 days ago. Maybe I'll put in another new spark plug to see if it gets fouled again.

Carbon Fouling Plug