How do I know which stroke sparks on my 96 Suzuki 250 2 wheel drive quad. I am putting the cam in as pictured but how do you know when you are at true TDC when its firing and the valves should be shut? You are supposed to set the cam at TDC but it has to be the right one . . . so how can you tell when its the one that fires?  

I may be talking completely out of my rear here - I don't have a Suzuki anything.  If anyone in the know differs please set the record straight.

My four cycle quad fires at the top of every stroke including exhaust.  Why not?  If everything is working there is nothing left to burn on the exhaust stroke anyway.

In order to prevent sparking on the exhaust stroke there would have to be a divide by two scheme somewhere since the magneto is mounted on the crankshaft.  A divide by two ignition system would have to be more complex with no real additional benefit.