My sled started acting up the other day by missing a bit and backfiring,the last time out previous to this it worked fine but I topped up the gas at a different spot this time.The last time it did this it had a broken ring and cost me an engine rebuild so I started checking plug color,it was fine,plug caps and any other electrical connection easy to get at.Today I went over these things again and even replaced the cdi with a spare I bought a year ago,checked the connections with the coils and any other thing I could think of.After doing this it seemed to work fine I tried the sled around a field and it was fine so I loaded it up and took it to where I store it in between runs.I started it up and backed it off the truck and as I was putting it inside it did it again but by that time I did'nt feel like screwing with it any more.The TORS is bypassed from before so it is'nt affecting anything and I went over the wiring harness the last time the engine was out and retaped any chaffing I found and put some automotive wire loom over the whole works so I think I'm ok there.The only things I can think of that I have'nt done yet is drain the gas and try new stuff or check the connections on the mag or do a compression check.The symptoms seem to be most present at low revs or partial throttle and as I use more it almost seems to be less frequent.Anyone got any ideas as to what I may have missed?The engine is stock.Thanks.
yamaholic22
Active member
try cleaning the carbs
What are your air screws set at? You could try adusting them out a bit. I'd try them at 1 1/2 turns out.
Thanks for the input guys but I found the problem today it was a wire from the mag half chafed through and grounding against the jackshaft.I only found it because I was in the process of removing the carbs to clean them and noticed that the wires were awfully close to the shaft and wondered if this was where my problem was and sure enough.Thanks. 
yamaholic22
Active member
glad you found the problem, always good to get lucky and find it before you get too involved