Stumble at RPM
 

I have a strange problem going on with my 2007 163fml (200cc) engine. It slightly stumbles at a certain RPM. From WOT it pulls hard until about 3/4 of Max RPM, it stumbles a little until the rpms go higher, then it clears up and pulls hard again to redline. It does the same on all 4 gears.

WOT pulls hard in all gears except for a small stumbling in upper RPM range
1/4 throttle 1/2 throttle and WOT it runs great. Doesn't seem like a jetting issue

Any Ideas? Maybe something electrical? CDI is new

Have you changed the spark plugs? As ignition coils age, they can fail to completely charge after the last spark is sent off to the plug. This usually shows up from mid range into the top end running. Also, check for a weak battery and charging system. The CDI usually fail and completely quit running. There have been a few oddities with some giving crazy running issues before failing completely.

Some great ideas! When I replaced the CDI it ran a hell of alot better. And now I have this issue. I have a brand new ignition coil I'll try and swap it along with a new spark plug and report back tomorrow.

The coil is gonna be a pain....

The ignition coil fixed the problem completely! Its strange that both parts went bad at the same time, but i did go through alot of water for a prolonged period when i was riding in a creek. i hope this helps someone. If you have an issue at a certain RPM, and not related to throttle, its may be the ignition coil and/or CDI