View Full Version : Two stroke help

June 12th, 2015, 10:00 PM
I need some help! My son's Kawasaki 65cc dirt bike is acting up and I can't figure it out.

When over 2/3 throttle or more, even under almost no load, it bogs, sputters, and occasionally backfires.

I'm running the same jetting as I have been for the last 3-4 months with no issues. I did a top end about 2 months (20 engine hours) ago. I'm seeing about 105 psi of compression but I haven't validated the gauge at all. I dumped the fuel tank and flushed out the dirt I found with fresh fuel. I installed a fuel filter to prevent any possible problems. I pulled the carb and main jet and hosed down all the passages with choke/carb cleaner. I replaced the spark plug. I made sure the exhaust pipe was free of blockages.

After all that it is slightly better but is still having problems. I'm at my wit's end and my son is supposed to race on Sunday. Is there anything else I should look at?

June 16th, 2015, 04:39 PM
i would try dropping a size or 2 on the main jet and see how it does. in general for jetting the first 1/4 of throttle is controlled by the pilot jet, fro 1/4-3/4ish is mostly the needle, 3/4-wide open is the main jet. each will effect the other slightly as well. other things to look at are the air filter and silencer packing.

June 16th, 2015, 09:15 PM

Jim B
July 7th, 2015, 11:29 AM
Ever get this resolved?