spark plug

[kevinsudd]

ok besides oil coming up into the cylinder and bad air mixture. what would make plugs get a black flaky residue on them. i have tried everything i can think of. turning the air flow scre 1/8 turns. readjusting floats. carbs wont sync becuase of this fowling. i look at the spark and the inside cylinders seem weak. yes i can probably bring it to a yamaha dealer. but i hate to since i bought this bike for $350 and its a hobby fixing it myself. this is what i have doen. replaced exhaust, stage 1 carb kit and cleaned them while i had them out. all new intakes and breather is tight and new air filter. the only thing i havent done is igniton. all is original parts

[Redbaron]

Spark plug

That sounds like gas fouling, you may have gone too big with your main jets, or you may need to reclean that carb. Is it only the one or do all load up like this? I had one fouling in the same manner, i went to one step hotter plug, no this didn't fix the problem but it did stop fouling the plug. Am working further toward a final solution. I run indy filters and harley fat boy mufflers, set up on a four to two configuration. Fouled number 4 several times before i went to hotter plug. HTH

[kevinsudd]

it fowls 3 of the four. i had to go to a 4 into 1 exhaust

[Mike Hart]

"stage 1 carb kit"? What manufacturer?

If you replaced your pilots w/ ones from that kit, put the stock pilots back in. If that helps at all but you're still fouling, put ALL the stock jets back in.

[tiel]

I had the same problem, I re-jetted according to the thread about jetting. I went up on the mains (4 sizes) and followed the suggestion about going up one size on the pilots for every three on the mains, I found that while the main jetting was great the pilot jetting was all wrong. I put the "stock" size pilots back in and re-adjusted the mixture screws and all was good again. I did go to a one step hotter plug as well.

As far as three of the four fouling, I woud look at the passage in the one that isn't fouling it may be partially clogged? I would also really check your ignition closely. If it was all four the same then it could be as simple as jetting, but since you have problems two fold. You need to get all four the same then fine tune!