I've got a '93 XJ600 that I bought for my wife. It has less than 5000 miles on the clock but had no engagement between the crankshaft and the countersprocket. I took the bottom end apart and found that the teeth on the starter clutch wheel gear were mashed to a pulp around about half the diameter of the wheel. In addition, there were a few broken teeth on the idler gear that runs off of it. There had been a tremendous torque load put to the starter cluch at some point since I also found other damaged pieces on the starter clutch assembly. I replaced all that were out of spec and carefully inspected all the rest of the transmission/bottom end. While there were chunks in the oil pickup screen and oil pan from the starter clutch, the main bearings looked fine and all the transmission gear teeth looked good. I cleaned everything and put it all back together.

I was unable to run the bike prior to purchase so I have no history to reference as far as other problems.

First, when I lit it off for the first time I have quite a bit of noise coming from the clutch area that gets a little better when I pull the clutch lever in. It's getting better the more I run it, but still too noisy for my taste.

Secondly, there is a loud howling noise that briefly comes up when the rpms get above 3000 or when backing off the throttle. It sounds like a dry bearing. Like a dry rotational vibration. It's quite obvious and alarming. It only lasts for a few seconds then goes away once the bike is back at idle.

Third, there also seems to be a lot of chain noise in the crankcase.

I've reviewed everything I did and don't see an area that I missed. The clutch plates are in spec and everything seemed tight when I put it together. Any input would be greatly appreciated.

Brian

I recently started hearing this - I don't know where it is coming from - but as you say - it starts at a specific rpm and doesn't happen above or below it. It also doesn't always happen - just sometimes.

A dry bearing would suck - have you done an oil change lately? I'm considering doing a change after only 6000km - I'll be looking for metal filings etc. Last time I changed the oil I noticed a few specs, but nothing really out of the normal.

On the chain noise issue - some of that is just being an old bike. Lately I've had the top off, done the valves and adjusted the cam chain. The cam chain guide does wear, and mine looked ok for another year or two. The cam chain stretches over it's life and at some point doesn't run as smoothly as a new chain. Replacing the chain is preventative maintance that I'm going to do next time I do valves, or in 2 years. Which ever comes sooner.

(EDIT)
My mistake - I assume an older XJ model - yours is almost brand new!!!