Cannondaleriders

Hey guys, went out to St. Anthony's for a week last week and had a killer time. Half way through the trip, my quad started acting up. When its hot, over half throttle and it will pop and die, sometimes I can pull in the clutch and save it and it will idle. Whats weird is that I can start it back up fine and idle it back to the parking lot, but anything over half throttle and it will pop and cut out and die. The quad also has to be very hot for it to do this, after sitting in the parking lot for an hour or so, I can go out and beat on it for 5-10 minutes, and it runs perfect, but after a while it will start popping again...

I of course had a bin of spare parts, I've had a similar issue in the past and it was the voltage regulator, changed it not a thing. Also put a fresh fuel filter and changed the fuel pump, didn't fix it. Strangely, all this happened after I pulled the tank to do a plug check, so I thought maybe I kinked a fuel line some how, but its not. To me it just seems like its fuel related, because it only does it when its hot, I don't think the heat would make an electrical issue show up.

It almost seems like its vapor locking (had issues with that in past also), but whats weird is that I can idle it back fine, plus I have gutted fittings, heat shield wrapped tank, and my header is wrapped. Definitely shouldn't be vapor locking... Any ideas??? Sorry for long post, I just got back the other day and I have a race tomorrow, and would like to get it figured out.

What does the air filter look like? I've had a filter that was so old that it got plugged up (even after cleaning it) that the motor wouldn't accept any throttle after idle but it would idle all day long. So I put a new filter in and it ran as good as new. Sounds strange but that was the problem. Had this happen while trail riding.

Filter is good, I changed it out in Idaho thinking some how that might make it act up. It has something to do with heat, I'm clueless, but I need to figure it out soon, race tomorrow...

Sparkplugs can also act crazy when they get hot. We had that once with a KTM, ran like crap when the engine was hot, new sparkplug and the problem was solved.

Guess I never thought of that. I'll try that, thanks.

I've had a coil do similar. It was tough to diagnose, but when I went to check the plug again - the coil came out in two pieces...

Your flywheel my have started to spin. If you marked it with a scratch or marker, check it. It may have spun just a hair.

Actualy, you can see on the oustide of the flywheel when it is about to spin. You will see small lines (cracks) from the center steel part going into the aluminum. I can post a picture of it, have a flywheel here like that.

And bad coil is also possible. Crazy stuff can happen with coils and sparkplugs.

For a plug reference run an NGK CR8EK or CR8EIX (Iridium)...