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Q: I recently purchased a 1973 Kawasaki 350 S2A triple. I'm using regular gasoline. The issue I'm having is a pinging noise coming from cylinder No. 3. This pinging noise is more noticeable at low rpm (below 2,000rpm). What could be causing this problem? — Mario/via email

A: I suppose there could be a carbon spike glowing and pre-igniting cylinder No. 3, but having it happen at idle makes me think it's something else, like a bearing rattle. Pinging usually occurs under moderate throttle while choosing a gear a little higher than conditions require. A mechanic's stethoscope, available at Harbor Freight or any auto parts store, is a handy tool for chasing down odd noises coming from your engine, but a long screwdriver held against the engine case with the other end pressed to your temple can give similar results. What you'll be listening for is the frequency of the sound. Is it every revolution or one in three? If you hear the sound on every revolution, then it's probably bearing related, but if you only hear it every one in three it would be specific to that cylinder.