Quote Originally Posted by green91
speed is right, at 900rpm you should have a revolution of the crank every .06 seconds. i typically use a seiko stop watch.
Exactly. It sounds to me that the spark plugs may not plugging properly. Either air is getting past the plug or the spark is not being suppressed. If the light of the spark is escaping at the plug then it can't be detected at the crank. I'd suggest removing the spark plugs and coating the threads with a thread locking compound to seal it so the light then can come out the crank and be properly timed. That's where a timing light comes in handy that the high end performance shops use.