98 SPX only firing on 1 cylinder (I think)

[Gone Fishing]

The machine seems to be down appox 50% on power with a top end of approx 25 - 30 mph and is not revving up to normal RPM.
Started off checking the spark plugs and 1 looks fine and the other was very clean with the exception of the porcelain which was black rather than a normal tan color and was wet when I removed it. There does not appear to be any heat in that cylinder. Checked compression and had 120 psi in both cylinders so the engine does not appear to be hurt. Before getting into carburetion, I would like to verify that the ignition system is working properly. The MPEM was recently replaced so that should be good with the exception of the timing may be slightly off but I wouldn’t think that would kill 50% power. I changed spark plugs with no effect. If the ignition coil was the problem, since there is only one coil, wouldn’t it affect both cylinders or could that still be the culprit? I haven’t checked the plug wires yet but plan to tonight. Any thoughts on other components that may be not firing 1 cylinder? I sure appreciate any help!
John

 

[kustomkarl]

John, it sounds like a carburetor problem.It sounds like you need to remove the carburetors and clean them. If you're careful and don't tear or damage the diaphragms you won't need to buy a rebuild kit. Pay attention to the internal filters too.

Karl

 

[derek]

there are 2 coils. put plug on the coil wire that isn't running. ground the other one on the ground lug. crank starter. see spark? got spark. no see? no gots. now you can look into the carbs.