I was riding my banshee down the road one day and i let off the gas and i heard a loud wine and it made a loud pop like a backfire and just died. Well the same thing happend to me before on my blaster so i knew the sound. My flywheel key sheared off and then it backfired. It was a crappy vitos 4 degree timing key. Well i put a new flywheel key on it and it wouldnt start still so i just assumed that it blew out the reeds when it backfired so i spend 200$ for delta 3-reeds and i changed the plugs and everything and then i started it right up and then it ran for a second or 2 and then died. then i got it started again and it was like one side would just keep fouling out and it wouldnt idle at all. finally after i did that awhile it popped really loud and a ball of fire came out of my tailpipe. i have black burnt oil on my pipe where it goes into the silencer. i pulled out the plugs and they are wet and have black oil on them. After i change them it starts right up and runs for a couple seconds and dies. My second guess was crank seal but i still have all my trans fluid and everything and the entire motor is barely broken in. i re did the top end and put all new bearings and seals in the bottum. my mods are as follows

toomy t-6's
stage 4 port
trinity 2 into 1 carb
35mm carb with 50 pilot jet and 175 i think main jet.
k&n filter
b-cool head with 20cc domes
v-force delta 3 reeds

My fuel is 93 octane with 32:1 klotz oil.

Any ideas? Im clueless!

 

Maybe something happened to the CDI pickup? Do you still have good compression on both sides?

 

I think i have pretty good compression. i dont have a compression tester but it feels ok. I was messing with it today and i got it running on the right side with no problems and had no trouble and would just fire on the left every now and then. and then all of a sudden its a big pop out the left exhaust. Well i pulled both plugs out and cleaned them and checked the spark. I got a great big blue spark on the right, then nothgin on the left. So i put in another plug on the left and got a pretty small blue spark. So i checked my power to the coil and it was liek 133 volts or something like that. So would that mean i have a bad coil? But why would that just happen all of a sudden after i sheered the key? thanks alot!

 

did u check and see if maybe your flywheel wiggled and maybe smacked your stator.

 

i checked everything out and there doesnt seem to be any damage. i checked the resistance and it all meets specs. im getting power to the coil when i kick it over. the right has a big blue spark and the left has a tiny almost gone spark. So i checked the resistance to the coil and it reads its open. so i just ordered a new coil. Hopefully itll take care of it. if not i think it must be the stator.

 

Well, on most CDI based 2 strokes, the CDI fires both plugs at the same time. The Banshee is also setup this way. You can swap plug cables between the cylinders and the other side should start running. I am about 99% sure that the new coil will fix your problem.