Motorcycle Repair: 82 Interstate Engine noise, vancouver bc canada, main bearing

Question
Al Beix (pronouced Bikes :-) ) here in Vancouver BC Canada.

I recently bought an 82 Interstate with an indicated 54000 KM on it. The engine runs fine has 60+ lbs of oil pressure when cold and 45 at speed when hot - About 20-25 at hot idle. it runs fine, pulls strongly and does not use excessive amounts of oil.

The issue I have is that at 4000 RPM and above the engine has a "rattle" which sounds deep enough to be a rod or main bearing, but if such were the case it would be prevalent at all speeds under load and the engine would have poor idle oil pressure. The noise starts at about 3750 RPM and comes to full cry by 4000 RPM it does not get louder at higher rpms and  in no perceptable way does it affect the performance.

Any thoughts on what its source might be?

Thanks in advance for your time.

Regards


AL Beix

Answer
Hi Al,

Interesting last name, Sir.

It's possible the source of the rattle may be connecting rods, pistons, primary chain, or other engine parts.

The term "rattle" as described sounds unusual, no pun. Noises must be heard and investigated to locate their sources.

Respectfully,
Mark Shively
Dayton, Ohio