Motorcycle Repair: 450 Suzuki Twin Engine Mystery Noise, harbor freight tools, piston slap

Question
Three summers ago, my 1981 twin 450 Suzuki developed an intermittent engine noise at around 19,000 miles that sounded to me like piston slap.  I could not tie it down to a cold or warm engine and twisting and releasing the spring loaded cam chain adjuster had no effect.  Applying and releasing the clutch also had no effect.  The noise was audible at idle and to a few thousand RPMS but not higher.  It made the noise on most days but not all.  Last summer the noise was gone; the engine sounds like new again.

Oil and filter changes have not been neglected.  The engine was occasionally taken to over red line but not until a few years ago and I avoid doing that now.  Otherwise the engine was not often taken to red line but mostly kept a few thousand Rs below that.

I am trying to recall now if the noise was at engine speed or cam speed but can't.  The engine runs so fast that it was hard to judge.

What do you think was causing the noise?  Piston slap?  Cam chain?  Clutch basket?  What else?  Could the cam chain adjuster have been somehow stuck on a burr or a wear groove?  Can piston slap go away?

Answer
Hi Henry,

Diagnosing sounds is impossible via allExperts. Ya gotta hear sounds to locate the source.

Try using mechanic's stethascope (Harbor Freight Tools) or suitable tool such as a long screwdriver or rod held between your ear and suspected parts. These items conduct sounds well and are very helpful tools.

I suspect combustion detonation as the cause of the sounds, especially if the sounds come and go. Switch fuel brands or try a higher octane fuel and note any changes.

Piston slap sounds may fade. Usually unpleasant results soon follow these sounds.

Respectfully,
Mark Shively