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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.
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93 octane fuel to stay away from alcohol, spark plug proper heat range, a 3 cylinder point and timing check. Check the cylinder nuts for proper torque, copper cyl gaskets can leak, a compression test on 3 compared to the other two cylinders, followed by a crank seal check and a cyl. leak down test. One of these should expose your ping problem... good luck..
A couple of things, use 93 octane fuel to stay away from alcohol that can make these bikes run hot and noisy..A little more info would be great however, first the obvious, make sure the proper heat range plug is installed, perform a check up on 3 cylinder point and condenser, gap and timing, also check the head gasket, those copper gaskets can leak with the low torque cylinder nuts making strange sounds. If all checks out ok, the next thing is a compression test on 3 compared to the other 2 cylinders. And finally a leak down test to check the outer crank seal for leakage. I suspect one of these tests will find your problem... good luck
I have one of these bikes!!
I have to point out, on a 2-stroke everything happens with one revolution of the crank. It makes sense for a noise to be 3X per revolution, but I don't think you really meant to say there would be a noise every 3 revolutions. I do a worse job of connecting my thoughts to my words every day, but I think your statement might be rethought.
Why not try premium gas and see if it goes away?
Why not try high test gas and see if it goes away?
Why not try premium gas and see if it goes away?