I have been working on sleds alot of years, and do it as a side business, but I have never ran across a problem like this. I am hoping someone has and can give me a little help.

This machine is a 93 750 storm. For some reason it seems to loose the pto cylinder off and on. It will not fire when idling, and will pick up as the rpm increases. It is very hit and miss. I have been through this thing a hundred times. The last time I had it running and idling good. I drove it from the front of my house to the back, let it sit for a few days, and then it started doing it again.
Carbs are clean, it seems to spark on the head, compression is good. I just can't figure it out. I mean air, spark, compression, and fuel. That is all it should need. The only thing I can think of is a weak coil. They seem to check out, but I don't have the proper manual, so I can't be sure. If anyone has any ideas at all, please fire away. Thanks.

Are you sure that the spark plug wire boot is always making good contact. I am just thinking that maybe once the coil is making more juice, it may be more able to jump the gap of an ill fitting plug boot. I would check it out very closely, or replace the boot in question. If I remember correctly, they are not real expensive.
Might be worth a try. Had to replace one on my buddie's Indy 500. His was occasionally dropping one cylinder for no reason. Turned out to be the plug boot.

Our F5 was dropping a cylinder at idle.

Compression, spark, fuel was all good.

Tore it down and something went through the motor,broke the bottom ring and scuffed the piston n cylinder. so it wouldnt idle (sometimes) on 2 cylinders, but it would run fine once over idle.

Thanks, unfortunately I put a new cap on.... No luck. I also tried a different wire from the coil to the cap. Same thing. I tell you this has really got me scratching my head.

check crank indexing. if not 120 deg apart can do very strange things.

could be one of the following:
1. cracked reed, especially at the tip
2. too small jet or screw adjusted too lean, or dirt
plugging up the idle circuit some.
3. idle speed too low

My dads 93 Storm does the same thing. I think it is just how they are. Cold blooded bastards those Storms are, but they run like a bat out of hell when everything's right.

Well, I finally got it up and running. I am not sure what it was. I think it may have been a bad ground. That is the problem when you work on about 10 things at once. You are never sure what exactly the problem was. Anyhow, thanks to all that helped. It is great to brainstorm ideas when you are stumped.