I just got through redneck rebuilding the entire bike from the frame up.
I painted the frame and all pieces I could get my hands on.

Well today I got my head gasket and my clutch cover gasket changed and now the bike hesitates to start. (took five minutes cranking the starter and about five more pulling the rope) She starts and still smokes but I realized that my cylinder to crankcase gasket is shot.

The problem I'm having is that when it does start it goes crazy and revs up to what would be about 1/2 normal throttle and won't go down. The air/fuel mixture screw and the idle set screws don't have any effect on the idle at all. I tried them both all the way in, both all the way out, and one in and one out but no change... I know I'm going to have to change the jug gasket but whats up with the carb?

 

If the cylinder gasket is bad its sucking air there and can cause the problem you discribe, try spraying carb cleaner on the gasket , see if engine speeds up or slows down, that will confirm your leak.

 

And it was a 40 cent part. The flywheel woodruff key had moved not even the thickness of my fingernail. I burnt the starter clutch up figuring it out. If it doesn't start the first 3 to 4 cranks somethings not right, look again. Whatever you do, don't keep cranking it over and over with the electric start hoping a miracle will happen and it will just run right, check that key. Mine fired up after rebuild, after countless cranking and backfiring, idled to the moon, wouldn't matter what kind of adjustments I made to the carb, ran HOT HOT HOT. I'm still amazed after all the years i've worked on these things i've never seen one do that in that fashion but a cheap enough fix i guess. I've seen them sheer keys but not move a hair and not run, they are picky. Still cost me a starter clutch though. Make sure you use an impact when you put that magneto back on or i'm willing to bet it will sheer the key again after changing it. It took me going through three of them keys to get it right but the quad seems solid now. I bought some from the hardware store and filed them down to fit right, I didn't buy the ones from the dealer. Probably should have.