Help judging crank sound

Miguel P

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Sep 10, 2017
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Wizards of happytimes,

Could you take a second to listen to the posted video. Is it a normal noise youd expect from rotating the crank. I understand the clicking sound is from the magnet, the other part of it coming from the crank is a little louder in the actual video thats why I went so fast as to make it more audible. I've never done this so Im not sure how it sounded when new (9 months ago 2000km ) and am installing reeds which will change the sound im used to.. Am I being paranoid or should it sound completely smooth? Thanks

 

crassius

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Sep 30, 2012
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first, magnet should never make a noise - video doesn't load properly, so can't tell anything else

I'd suggest putting piston at top and see if you can pull/push and find any up/down play in bearings.
 
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Miguel P

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Sep 10, 2017
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Thrid time is a charm?
Crassius there is NO up/down play at any position. Perhaps 1-2mm left/right tilt play.
The clicking occurs at recurrent positions: BDC and ~15° from TDC. I used to think it was a signal for ignition until I found there isnt one from the engine.
I'm mostly worried about the smoothness of the revolutions

 

crassius

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Sep 30, 2012
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definitely not normal, and there should be no projecting pieces in bottom case that could stick out and make a noise like that - hopefully, you can open all the covers and track down where it comes from as if not, you may have a bearing cage loose in one of the mains which will be REALLY hard to deal with

maybe something stuck to back side of rotor magnet that is hitting stator? or maybe something between teeth of small bevel gear that comes around once per crank turn?
 
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Miguel P

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Sep 10, 2017
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Are you refering to the clicking sound or the other noise that is constant? (the sort of non-smooth, rubbing sound). So the second one is the new occurrence and appeared two days ago when I rode in pretty heavy rain (which I never do) so thats why im more woried about that. At the end of that day I noticed a more rattly noise with the engine running and thats why I checked the crank. It wasnt hotter than usual nor less power except during heavier rain but at the end of the day power was fine (no rain).
Is it worth it to try to "wash" the case somehow? like a couple of times fill it with fuel and shake it around. ill start by trying magnet and gears though
 

crassius

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a good visual inspection while listening closely should find a noise that happens once per turn
 

Miguel P

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Sep 10, 2017
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Interesting situation apparently both sounds may have the same culprit?
Not sure, but removing only the magneto was sufficient to solve the clicking sound:
And the rattly sound of the crank Im thinking is from the bearing on the side of the magnet. It seems harder to turn, looked dry and brown. The clutch side bearing was more free spinning looked dark and wetter/oilier:

Can an over tightened magnet increase stress imposed on the bearing? ill get 4 OEM SKF 6202 2RS C3's while i'm at it. Is it worthwhile not removing the inside bearing covers thus preventing debris from messing with the bearings or is fuel lubrification essential have you tried this?
 

crassius

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Sep 30, 2012
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my first thought would be to look closely at the stator of the mag to see if there are any marks that would indicate that rotor was rubbing on it - any rubbing there might cause the bearing to heat up for that brown look

as far as bearing is concerned, the factory always removes the inside cover, so I'd guess they found a reason to do so
 

Miguel P

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Sep 10, 2017
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All installed now, new bearings are definitely smoother. Whish I could change the conrod bearing but thats not an adventure I want get into for now.. Then realised I threw the crank wheels way out of alignment during closing of case.
Unpinched it by snugging a bolt with a nut in between the crank wheels and unscrewing them apart with two wrenches, effectively pushing the wheels into alignment (somewhat) at least until theres very little play in small crank gear and no difference in space between wheels during rotation. Hopefully its at least as good as it was..

The clicking noise was definitely the stator, tried pulling it out and re-installing a bunch of times, tried grinding it down, changing bolts, thought they could be crooked.. Had given up and started into alligning the crank.. As last resort first video on YouTube when searching for clicking noise of this dude high as a kite talking to his cat. Showed snugging two business cards between stator and magnet and THEN tightening the screws. Worked perfect!

Just to throw another windowed piston example out there, since this was all to prepare for reed installation..
IMG_20180315_231704_5.jpg


Anyways, thanks for your attention. +1