arcs between exhaust and an engine mount

[LittleTimmy52]

I have a standard rujn of the mill cheap 100cc kit on a bike jsut with different head and pipe, the pipe didnt fit to wel but its on there, it goes down past the front mount up to the head it goes past and back, the pipe is paper thin clearence between the mount and its touching the big cnc compression head. by the mount it is sparking like the spark plug at basicaly the same time as the plug. It still runs fine, i think anyways. why would it be sparking? and how do I stop it? also the boot is cracked but i dont see arcing at the head.

 

[wrench]

Could be a few things going on, Here's some things you can check

Replace that cracked S/P boot, Current might be getting thru and you see the spark jump from the head to the exhaust pipe

If your using the cheap China S/P that came with the engine, Throw it away and buy NGK

If you have rubber on your engine mounts ground the frame to the engine

Make sure the S/P threads are the correct length
If the S/P threads are short and the S/P hole in the head is long, It'll cause the spark to jump to the head, thus spark jumping to the exhaust pipe

Also if the S/P gap is too big the spark can jump from the electrode to threaded part of the S/P causing the spark voltage to travel thru the head Then you see it jump from the head to the exhaust pipe
S/P gap .025" - .030"

Maybe a couple other things having to do with the magneto that I'm not aware of