Re: Strange Carbon Pattern on Piston

• Author: babooze (---.hawaii.res.rr.com)
• Verified User: babooze
• Date Posted: 05-13-08 06:48

not too sure about this but, check to see where you start to spark… if it’s too soon then it may cause it to have deposit build up only on the bottom half of the piston….because fuel is not fully compressed when spark occurs, too advance timing can also cause your idle to be erratic or not idle at all (only if your timing is extremely advanced this could occur)
....also you may be running too lean(meaning too much oil)...leaving you with unburned oil/gas mixture causing deposit to build up. how’s your spark plug is it black, wet and sooty or nice, dry and brown?....not sure about this, just guessing….

but then again carbon build up may just be normal(deposit shouldn’t be caked on, but deposit will exist).

“There was A LOT of carbon buildup on the piston.”
crappy/too much oil could be reasons you have a lot of deposit.
jetting could be wrong. and your idle problem may be your idle jet…. does screwing in/out your air/fuel mixture screw have an effect(rpm’s) on your bike?

also as Paz stated a photo would be really helpful

here’s what you can do on your idle problem, if your idle screw is turned in all the way and still no idle. have someone crack the throttle open just enough to keep your bike running on the stand. while holding it at a steady rpm try adjusting the air/fuel mixture screw by turning it in/out and see if it has an effect(rpm’s) on your bike. if there’s no change in rpms at all, my guess is your too rich and you need a leaner idle jet or something may wrong with your idle circuit. your idle circuit may be clogged. if this doesn’t cure your idle blues then idk what it could be =(