Rubbing noise when shutting off

dusty · November 06, 2019, 07:27:52 PM

Hey again. Got an odd issue that happens occasionally when I shut my bike off (02 M620). It's not a grinding, chunky sort of noise, but it sounds more like a stunted metallic groan that lasts a half-second. Sorry, hard to put in words and it doesn't happen reliably, so I haven't been able to record it. I recently re-shimmed both sets of valves and confirmed that there was no rubbing on the closers (belts off and openers to the side), and the cam lobes look fine. Belt related bearings spin smoothly, though they take just a hair of force to get moving which I chalked up to old grease. All of the rotating parts that I can check seem fine as far as I can tell, so I'm not really sure where to look next. Oddly, it only started to happen after the most recent valve service, which called for some relatively significant adjustments. Any thoughts? I'm leaning towards checking the valves out again.

koko64 · November 07, 2019, 08:37:36 AM

Go over all the work you did for peace of mind. Where did the sound emanate from?

koko64 · January 08, 2020, 09:09:29 AM

Did you resolve this?

dusty · January 10, 2020, 03:07:11 AM

Oof, I wish. Got caught up in all kinds of holiday non-sense and it's been stored since November, so I've gotten to do nothing that I wanted to. I'll be pulling off the side covers some time this winter for paint, so maybe that'll be my valve day. Thanks for your thoughts though, Koko!

Speeddog · January 10, 2020, 08:41:16 AM

Ducs can make that sort of sound on shutoff, they come up to TDC but don't make it past.
The engine starts to turn backwards and backdrives the starter motor through the sprag clutch.

DuciD03 · February 11, 2020, 07:31:42 PM

Quote from: Speeddog on January 10, 2020, 08:41:16 AM
Ducs can make that sort of sound on shutoff, they come up to TDC but don't make it past.
The engine starts to turn backwards and backdrives the starter motor through the sprag clutch.

-dam- how do you know that (shit!)!

ya I could see it; would that back groan damage anything? Guess its been doing that for on many Ducs for many yrs ...

Speeddog · February 11, 2020, 07:51:46 PM

First time I turned a Duc engine backwards... "Hmm, yeah, heard that sound before."

No damage that I've seen or heard of.

Seen a locked up sprag that backdrove the starter while the engine was running.
Starter definitely didn't like that.

koko64 · February 17, 2020, 04:04:45 AM

Thinking about this, to me the compression cranking sounds more like the chugging of a steam train. The term rubbing threw me.

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Rubbing noise when shutting off