2007 Yamaha Raptor 80 wont run at all

[MoMike]

07 Raptor 80. Had old fuel in it. Got it running on the old stuff and left it idleing while I ate dinner. I looked out and it had a lot of smoke coming out of the exhaust. By the time I got out to it, it had stalled and would not restart. Drained the old fuel and still wont run. Not even a backfire. Rebuilt the carb. Still nothing. I'm not an idiot but this thing sure makes me feel like one. Almost seems like no compression. I cranked it while the carb was off and there does appear to be vaccuum. Definately not the starter clutch.

Any help is greatly appreciated.

Thank you,

Mike

[DirtDemon]

Have you tried a new spark plug? You say it feels like it has no compression, a compression test would not be a bad idea. When you rebuilt the carb, did you make sure to clean all the jets and passages in the carb and make sure the float is moving properly? If the float valve is stuck in the inlet, no fuel will enter the carb. You also want to make sure that the fuel petcock and fuel filter (if any) are not plugged. Have you checked for spark? Have you tried starting fluid?

Edited September 19, 2010 by DirtDemon

[MoMike]

Yes it has spark. I don't have a compression tester small enough to see what it actually is. Float is not stuck. When I rebuilt it I have the NAPA 1 gallon carb soaker can with basket. It does a real nice job. I guess my next question is this. Can that cam chain slip and throw the valve timing off and if so how do you set it?

Thanks,

Mike

[DirtDemon]

I appologize for the long wait for a reply, I have been without my internet connection for a few days.

The cam chain can slip and throw the valve timing off, but if it did, it is not as simple as re-setting it. If it did slip, there was a cause and that cause needs to be fixed, possible causes would be worn sprockets, stretched chain, faulty, weak or improperly adjusted chain tensioner. There are two vavle inspection covers, one on each side of the head. You can remove these and check the vavle lash, get a ballpark idea of where the valve timing is by making sure that both vavles are completely shut when the motor is at TDC. I would recommend checking the valve adjustment, also. However, before you start looking into the valve timing, I would rule out the possibility of there still being a problem with the carb. Dipping the carb in a bucket may not get all the gunk out of the jets and passages. These places often need to be manually cleaned out, poked through with something and then maybe blown out with compressed air. Did you look and make sure the jets are clear? Have you tried getting it to start using starting fluid? If it will start and run for a sec using starting fluid, then your problem is that you aren't getting fuel. If it will not start even with starting fluid, then obviously your problem is something else. Another possibility is that the timing key has sheared off, and the spark timing is off.

[MoMike]

I really appreciate your in depth reply. No it doesn't run on starting fluid. I am a mechanic by trade, just not on motorcycles. Theory is still the same, fuel, squish and fire something has to happen. Problem is no squish. I had the head off. Cylinder is not scored and valves seem to be seated. Metal head gasket so i'm assuming it's reusable? Sprayed a coat of copper on it and and re-installed. Cranked it over without the carb on, just trying to get the squish back. Has vaccum on the intake tho I don't have a way to measure how much and when I put some oil in the cylinder it pushed it out the exhaust port. This is why I think the cam timing is off. At TDC there's a mark on the cam gear and it lines up with a mark on the cover. I know i'm missing something, just don't know what it is.

Thanks,

Mike

[DirtDemon]

When you line the mark on the cam up, is there a flywheel mark to reference so you know the crank is at TDC as well? Many machines will have a plug that you take out to give you a view of the flywheel for timing purposes. Obviously, if the crank is not at TDC as well, then the cam marks lining up don't mean anything. Given everything you have said, I am inclined to agree with you, if there is no squish, and the vavles, piston/rings and cylinder are fine, the most likely culprit is valve timing. I have heard of people re-using metal head gaskets without issue, most of them do the same thing you did, spray copper on it. As a general rule though, it is not really recommended.