Motorcycle Repair: Evolution engine problem, drag pipes, evolution engine

Question
I have a 99 evo engine, points ignition, HSR42 carb. The engine runs fine until it starts warming up. As it warms the engine begins to misfire. (it feels as if the engine stops for a revolution then starts running again). As the engine gets warmer the problem gets worse, until it is a continuous misfire, I believe it is the front cylinder that has the problem. I have replaced the points, condensor, coil, wires, gas cap. Nothing seems to make a difference. I ran a compression test after the problem happened and with a hot engine I had equal pressur in both cylinders (just over 90 on the guage.

Th engine is in a hard tail frame, I am running drag pipes with a short baffle. I had mufflered pipes before and the same thing happened.

Can you help, please.

Jim

Answer
First off I would do a Leak down test on both cylinders. if good then replace the points with a electronic Compu-fire ignition system, Change the plugs to a set of NGK BPR8ES spark plugs gapped at .040" and torqued to 22 ft lbs. Cleanr the mikuni low speed jet out and drop one size on the main jet. Check your groung wire and battery cables and battery ground to Frame cable. Johnny