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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: K75user1979 on June 07, 2024, 11:33:47 AM
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Good day/evening!
I just finished assembling my k75s after changing the alternator shaft seal as oil was weeping from that area. I also disassembled both the alternator and starter motor for inspection/cleaning.
When I removed the alternator drive dog, I rotated the engine clockwise with a ratchet, before jamming a piece of wood in there so as to remove the nut. When I reassembled it, I rotated the engine counter-clockwise in order to tighten the nut, before jamming that same piece of wood in there to tighten the nut properly.
Started her up, noticed nothing at first then a vibration at different revs.. on the road I noticed a grinding sound which came and went depending on revs. I probably rode 500m, maybe more than I should have although power seemed ok and I just thought something was loose. It was definitely a new and noticeable sound. On getting home I let her idle a bit and tried to pinpoint the grinding sound, also noticed that the idle was rough, on revving the engine I heard more abrupt crunching as if a chain was slack or a gear not right. I turned it off immediately and that's that...
Do you think I might have upset the timing by rotating the alternator drive shaft in both directions and thus jumping a gear or something like that.
Should I remove the starter motor and see if maybe the splines were grinding against its gear, I'll probably do that anyway.
What damage could I have caused? It kind of felt normal on the road but in hindsight I should have not taken her out of my driveway.
Thanks again in advance.
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If you're lucky, it's probably that the alternator drive cushions within the alternator cup (housing) were misaligned with the driving dog during installation then damage occurred during rotation. Remove the alternator and take a look. The cushions are colloquially known as monkey nutz. You could have something like what I ran across a while back—quite a symphony of rattling and clacking.
(https://www.motobrick.com/gallery/4/1601-150823114721.jpeg)
(https://www.motobrick.com/gallery/4/1601-150823114803.jpeg)
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Thinking it may be the nutz, I just got the alternator out. Mnutz look fine apart from a smear of black rubber in the cup and outside on the housing. Something I didn't mention was that I replaced both alternator bearings of the correct spec, all seated correctlty. I thought that maybe something was sitting proud and rubbing but this noise I heard was something more mechanical from inside the engine, loose chain rattle. I'm going to reinstall everything minus alternator to see if any change just to rule it out.
My main concern was having a chain jump a tooth in the timing mechanism when I turned the alternator shaft manually, or is that not possible? I never made complete revolutions either way although I did hear something at one point which put that idea in my head that these things should be rotated only one way.
Those nutz in your pic look really mangled, I see that it took the guides away as well.. lots of debris no doubt.
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I had an epiphany, realised that the monkey nutz can only go in one way.. I hadn't really considered the orientation between the vanes. I had metal on metal with the nutz doing bugger all. An hour later and she's running sweet again. COuldn't get back here fast enough to deliver the good news.
Case considered closed.
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