You can't check timing with a timing light. Most bikes have fixed timing, it is not adjustable (at least not in the way a car's timing is adjustable). The only way to adjust the timing on a bike is to change the relationship between the cam and the crank by moving the timing chain on the sprokets. To check the timing you need to remove the cover on the left engine case (round aluminum with slot in it) and put a socket on the nut and turn the motor (counterclockwise I believe) while looking to see the timing marks. You need to see that the piston is at TDC (on the compression stroke) when the TDC marks are aligned in the hole. You also want to have your valve inspection covers off so that you can see that the valves are closed at TDC on the compression stroke and that they open and close correctly. You'll also be able to check the functioning of the decompression mechanism through the exhaust valve inspection cover.
(Edited, I was mixing up my bikes DR has only one hole in side cover)
ppe172 screwed with this post 04-27-2009 at 08:15 AM