Originally Posted by
YellowBlueBird
Have finally gotten around to taking the valve covers off of my saito 125a that has been backfireing. It appears that the exhaust valve is still closing as the intake valve opens. How many degrees of rotation should there be between one closing and the other opening?
That is normal, it's called valve overlap.
To visually check that the cam timing is correct roll the engine over to TDC of the exhaust stroke. In this crank position both valves should be open equal amounts, therefore the rocker arms should appear to be level with one another, as viewed from the front of the engine.