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Pinging or Detonation on Acceleration


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Hot weather is here and your motorcycle engine is making a new sound. It reminds you of marbles dropping in a coffee can, a rattly mettallic noise that sounds funny but you aren't laughing.
What you're hearing is "pinging" or detonation. It can be caused by a few things.

Using fuel that is too low on octane is one. Make sure you're getting good hi-test and a brand name. Sometimes the pump hose has as much as a quart of low test in it if they all come out the same hose and the guy in front of you used low test.

An air leak in the manifold will do it sometimes because it makes a lean mixture at low speeds. Also when the motorcycle gets really hot it will ping.

If you have good gas and the motorcycle is in tune, it may be necessary to back the timing off a degree or two if you are using a tuner to get rid of it. There are other things as well, like the ignition or voes switch malfunctioning that will cause it.

One more thing I'd do is to vent the right side gas cap by drilling a 1/16" hole in the plastic motorcycle part inside, in one of the 4 bumps surrounding the spring vent. This keeps the carburetor from starving for gas when it's hot and relieves any vacume that will cause problems with fuel delivery. Be careful not to drill all the way through the cap, only about 1/8" is neccessary.