Cutting out/Sputtering

[ZillaRider02]

I rebuilt the top end over the winter and changed my setup. Now running a Passion Aggressive dune port, stock stroke, NOSS Head w/19cc domes, Fireball Intake, 34PJ's (160 mains/52 pilots), clamp on K&N's, V-Force 3's. I replace both crank seals and bearings when I did the top end. Got it all put together and fired the engine only to find it was running on one cylinder. Tested the coil, it was out of spec, replaced it and was running fine. Took it to the dunes this weekend, it ran really hard for the first couple of hours, then started cutting out in the upper RPM's, 3/4 throttle or more. Replaced the spark plugs, did another plug chop, which showed the plugs a shade darker than a perfect tan. Bike was still cutting out, and then heading to the truck through the trails, it died twice. Both times it acted like you hit the kill switch. Kick it once, it fired up and ran. I'm thinking I've got electrical issues. Maybe a bad CDI? I still haven't determined what caused the first coil to take a crap. The stator is of unknown brand/wattage, but has been lightened. My next step is to check connections on the CDI, etc. Any more ideas???

[shanYE west]

I had a similar problem with mine. It ended up being the pickup coil gap was set wrong. With weak spark the bike will tend to favor one side over the other for some reason. Maybe the new coil bandaided the problem for a bit. :shrug:

[sheefreak]

Have seen failing stator act that way before. Sometimes when one component in the electrical system goes, it takes others w/it. I would check all your grounds and connections of course, then look into swapping out stator/cdi w/known good ones.

[J-Madd]

Have seen failing stator act that way before. Sometimes when one component in the electrical system goes, it takes others w/it. I would check all your grounds and connections of course, then look into swapping out stator/cdi w/known good ones.

 

 

I had a stator fail and cause your same problem also. Only cuts out a high rpms. Good luck. Looks like your on the right track to narrowing this problem down.

Edited May 16, 2007 by J-Madd

[Screaming Yellow Zonker]

one other thing you might want to check is the spark plug caps. Ohm them out. there should be resistance. 0 would be bad.

[ZillaRider02]

I had a similar problem with mine. It ended up being the pickup coil gap was set wrong. With weak spark the bike will tend to favor one side over the other for some reason. Maybe the new coil bandaided the problem for a bit. :shrug:

 

I was considering the pickup coil as a source of problem. I'll look at it for sure.

 

 

I had a stator fail and cause your same problem also. Only cuts out a high rpms. Good luck. Looks like your on the right track to narrowing this problem down.

 

The stator had some rust/crud on it where it had been cut down, and where the pickup coil reads the magnet. I sanded the crud off and seems to run a little better.

 

one other thing you might want to check is the spark plug caps. Ohm them out. there should be resistance. 0 would be bad.

 

The spark plug caps were new with the coil I bought straight from Yamaha. I would think they would be good, but it wouldn't hurt to check. Thanks Guys.

[blowit]

I was considering the pickup coil as a source of problem. I'll look at it for sure.

The stator had some rust/crud on it where it had been cut down, and where the pickup coil reads the magnet. I sanded the crud off and seems to run a little better.

The spark plug caps were new with the coil I bought straight from Yamaha. I would think they would be good, but it wouldn't hurt to check. Thanks Guys.

 

 

I would say if you have rules out the ignition coil, that sure sounds like a CDI problem. Just swap with someone and try it. You will not damage your buddies if something else is wrong. As stated above, check the plug gap. Set it at .020 and see if it changes, if not set it back and look elsewhere.

 

 

Brandon