My Monster ate something crunchy

[Gorgor]

Hi all,

I have a '98 m750 which had a really nice feel and ran pretty well when I bought it, rode it home and took it out for two rides of around 100 mi.

Everything felt and sounded great, until I parked it and my wife and I got ice cream, and when I came back to start it I heard a sound that can only be described as ringing at idle. It sounds metallic like what you get when you tap a gear with a metal tool, + it was clearly loud enough and new enough that it was not there when I bought it the bike.

The bike had been down lightly previously, and the clutch lever had been getting softer, so shifting was occasionally more difficult on this ride than it had been on the ride home.

I took it home and ran it, and it seemed like the ringing goes away off idle, basically 4 or 500 RPMs above idle and it's gone.

The ringing sounds like it's coming from around the starter area but I can't isolate which side.

I decided to check the oil to see if anything was being eaten up, and found chunks.  At that point I decided to open both sides to see if maybe it was the alternator not or something with the clutch, because the sounds seem to be coming from the clutch side primarily.

Saw nothing on the alternator side, but on the clutch side this is what I saw.

https://ibb.co/album/KFgF6s

That got me worried, so I started looking closer, and it got worse

https://ibb.co/QQV23G3
https://ibb.co/7tMvBWZ
https://ibb.co/1Z3K9Pf
https://ibb.co/4W0JtDL

Something appears to have been eaten.  And I'm not really sure where to start looking.

Thanks, any help is appreciated

Sorry about the links, still working out how to post pictures on the forum

[stopintime]

No bits in the oil? In the screen filter? (just under the clutch)

Did you remove the clutch basket? The heavy vibration damping springs embedded in the large clutch gear can break. I'm not sure you have those springs on a '98, but anyway... That often happen after they get shorter and finally break "free". Your engine might have eaten springs or the tabs supposed to hold the springs in place. The loose springs will stop rattling with some revs.

... and then there's all the other things

[Gorgor]

First, thank you for the very quick reply. Much appreciated. Second, yeah I checked the oil and the screen. There was a lot of ugliness in both places little chunks about the size of the head of a pin and they were non- magnetic. I have taken the clutch basket off as a matter of fact and all the parts looked like they were there but there's a lot of play in the basket itself and I don't know how much play is appropriate so maybe there's something missing that I didn't notice?

[stopintime]

I'm not a mechanic or otherwise expert, but I believe the basket and gear are riveted together and should be tight. Our engines misfire quite a lot and that makes them sound bad, especially on idle. Just a few more revs and it sounds and is smoother. That doesn't mean something is loose, but if the idle sound is very audible it is suspicious.

[koko64]

Fin ring is a thing, especially after the puks have dropped out. The puks space out the barrel fins to cut noise.

Piston slap can cause a ringing sound besides the obvious slap sound. The Piston skirts can clip the base of the barrels. I doubt this is the issue but it's hard from a distance to know.

Too much play in the clutch primary could cause more gear lash sounds. Describe the play again. How much wiggle at the periphery of the basket? Clutch nut tight?

Non magnetic would go against some parts breaking, but they may have dug into alloy case material.

Any play or looseness in the flywheel?

Let's hope those shards aren't from the oil gallery plug.

I've just worked on an M659 and it had four noises that I had to isolate. They echoed through the cases and cavities in a real cacophony making diagnosis difficult. There was roller bearing whine, clutch rattle, Piston slap and plain bearing chatter. Sometimes it's obvious and sometimes confusing. Concurrent issues are a curved ball. I feel your pain.

Keep digging and send more pics when you can.
If you're still stuck then maybe local members can point you to a good mechanic.