wouldn't be the tors. the tors would make the bike cut off.....
it is most likely an air leak somewhere. this means that your charge is running VERY lean due to air getting sucked into the engine somewhere and that is creating excess heat which will make the charge combust even w/o spark. it will also increase rev speed.
set up a fan to keep the engine cool while you test it. start the bike w/ a can of carb cleaner spray in hand. w/ the bike running, gingerly spray the carb cleaner around the carb boots, reed cage, exhaust, head, cylinder base and spark plug. these are all the exposed areas where you can have an air leak.
if the engine changes revs when you spray, you've found your leak, just check the area to make sure all the nuts are in place and torqued to the proper spec. if they are, then you should replace the gasket.
if the engine doesn't change revs, then the leak is probably in one or both of the crank seals. replace those and you should be good.