Crankshaft bearings

[Anonymous]

I agree with the "noisy GS syndrome" especially at idle. I've been told the cam chain tensioner is the biggest noise maker even when it's set up and adjusted properly. That said, I had an increasingly alarming knocking noise from the right side of my 850 last summer. Along with a gradual loss of power and an oil leak. I nursed it home and started tearing it down - convinced it was a bad rod or bearing. I found the exhaust cam hold-down bolts had backed off on the right side resulting in plenty of daylight between #4 lobe and bucket, causing the loud knocking , along with a valve cover gasket leak. Remarkably, (or predictably?) no harm done. The lobe face was not damaged, the camshaft not bent, and the bearing cap undamaged. New gasket and it runs fine. (All holddown bolts now Locktited!) Tough engines indeed!

[duaneage]

Never tried pulling a spark plug. What would be the problem you're looking for by doing so?

The noise is very distinctive and sounds like a bad bearing. Had another guy listen to it who has worked on a lot of m/c and jetski motors (not a pro) and it definitely sounds like a bad bearing to him.

When you remove the spark plug wire the cylinder no longer fires. This changes the load on the bearings, and if there is excessive play the noise may go away or at least get quieter.

If it is just as loud it is probably NOT a bearing.