Loss of Power and Hesitating at Higher RPM's

[backtrackbug]

At higher rpm's it really bogs and hesitates. I have checked my valves, they are set at .003 and .004. It has a brand new spark plug cap, cleaned the spark plug, tried two different cdi's, carb id fairly new and seems to be okay.

Only thing I can think of is the coil is starting to go bad??

Any suggestions on what else to check?

[albongo]

Running rich?

[backtrackbug]

No, the plug looked good. Ive had the carb dialed in pretty good for awhile now. For some reason my gut feeling is telling my either the coil is going bad or the plug wire is bad.
Im wondering if I can cut and use a plug wire from a car instead of the stock wire....

Also, it feels like there is a over all power loss through out the throttle range, but it only starts to bog and hesitate at higher rpm's.

[walleye1963]

Have you done any upgrade? Bbk? Might need a bigger jet size.mine did the same thing had to use open air filter.

[backtrackbug]

Its a 50mm bbk and a #90 jet. Stock airbox, no airflow restrictions, ported manifold spacer to match new intake on head. It was running great, then lost my insides to the spark plug cap, bought new one, but had wire strand stuffed into cap to get to store and back for about two weeks.
Maybe the 20 miles I did in those two weeks on a rigged up cap was a little too much for the coil somehow. Or maybe the 5 strands of wire in that "high quality" chinese plug wire is broken up enough somewhere that it is arcing at higher rpm's.

But just for backyard diagnoses purposes, I want to get ahold of a a car/truck plug wire and install it. Unfortunately I threw my old Jeep wires away last winter after a tune up. They sat around for awhile, then went to trash.

[walleye1963]

Just remamberd when mine did it I had to lower the jet size.just a thought.

[Deleted]

If you suspect it might be arcing...wait until it is very dark outside and run the engine while looking all along the plug wire, from the cap to the coil. Rev it up on the center stand and look very closely. If there is any arcing, you will see it. Make sure you know where to look as it will be dark or, use a flashlight to get ready, and then turn it off.

I have found many a bad plug wire on my vehicles this way...one was even a brand new wire but was leaking to the exhaust manifold! (Car engine)

This may or may not be it but at least you can eliminate it as a possibility for free and in just a few minutes.

Bill

[scooterpimp]

Adding a water squirt bottle (mist) to plug wire while under load will show up a bad wire quickly.

[Fox]

Did it do the same thing before you changed out the plug cap?

Possible suspects:

Cracked spark plug
New plug cap is no good/arcing as suggested earlier
Weak/broken valve spring(s)
Float level too low
Minor vacuum leak somewhere

If the plug porcelain is cracked then you could be getting arcing inside the fan shroud where you can't see it.

[iwiketuddlz]

I doubt it is arch kin ..... Think about how far a spark will actually jump when you hold the plug away from the head and turn it over???right??? Eh maybe im barking up wrong tree??