My '94 EX500 trackbike has a serious stumble in acceleration at around 6500 rpm under hard acceleration and thereafter is not as smooth as it should be. (Not fun at all in a corner) Bike was stumbling worse at 5000-5500 before I pulled the carbs, corrected the floats,cleaned and synched the carbs. Setup is 135 main jets, NGK D9EA plugs, Yoshimura pipe. When I pulled the plugs they looked a little sooty... My first guess is go back to 130 or 132.5 main jets, second is a hotter plug D8EA's (can someone tell me the difference between D8EA's and DR8EA's while we are at it?), third is new coils and plug wires. Any suggestions?
i had one that did that. i just kept it twirled up tight and rode around it it seemed to be a byproduct of jet kit / pipe
The DR is a resistor plug. Doesn't make a real difference unless you have a stereo installed. I had a simlar problem but lower in the rpm range. It turned out to be a blocked carb vent tube.
