Agree with Roger. Had an old British motorcycle which had a maddening miss.
Testing spark under pressure revealed the problem. Lots of wasted time
trying to chase down other causes.

surfturf


"Roger Derby" wrote in message
link.net...
Is one cylinder significantly cooler than the other?

Does shorting one plug make the engine stop?

There exist spark plug testers which test the plugs under (air) pressure
while you watch the spark. (Visit the maintenance shop at your local
small airport if the corner garage doesn't have one.)

Roger