Motorcycle Repair: Yamaha, metal particles, cylinder compression

Question
1982 Yamaha XV7  noise in back rear cylinder.possible wrist pin slape. What would cause this. Any way to tell without teardown of motor.

Answer
Hi Billy,

Remove spark plug and inspect for unusal operation.

Try cylinder compression and leak-down tests to determine condition of engine (cylinder).

Drain oil in attempt to see metal particles other than the usual.

Use mechanic's stethoscope to listen for noise. It's hard to locate exact source of noise with so many moving parts. Knowing the sounds associated with certain problems helps, but you be present to listen.

Try rotating the engine while spark plugs are removed. This is quieter than with engine running. Be sure to ground plugs to engine or frame to prevent CDI damage.

If these tests produce little intel on the cause, tear down is the key.

Respectfully,
Mark Shively