Rattling Noise From Engine

LastFreedom

New Member
Jun 17, 2017
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My bike has made a rattling noise since the day I got it, and it sounds like the gas tank vibrating on the top tube of the bike, but after insulating it, I can confirm that it is not. It's also not coming from beneath the clutch case either. I don't get any noticeable difference if I put my hand or a cloth on the cylinder either. It's not the exhaust (zeda expansion chamber), as it's tied down and does not vibrate, and all mounting points are rock solid from what I can tell.

I think it's coming from inside the actual crankcase itself, but I'm not sure exactly what in the **** is causing it.
Any input on what you think it could be? I'd like my bike to be as quiet as possible.
 

crassius

Well-Known Member
Sep 30, 2012
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enough grease on small bevel gear, on bucking bar, rub marks from chain inside drive cover, steering head bearings tight, crank arm bearings tight ???
 

LastFreedom

New Member
Jun 17, 2017
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The small bevel gear has plenty of grease, bucking bar is within status quo as well, and there is no visible damage on or from the chain. Steering head has been periodically tightened, no difference was made there. I'm not sure about the crank arm bearings, however. How would I get into those to check?
 

LastFreedom

New Member
Jun 17, 2017
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Crank arm is tight. It's a 3 piece sealed unit on a mountain bike. The noise is definitely coming from within the engine.
 

crassius

Well-Known Member
Sep 30, 2012
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if stator is not properly seated on the boss of the case, it can get rubbed by the rotor - if flower nut is out too far, it can rub inside the cover - does it make the noise when clutch pulled?
 

Rigz

Member
Mar 1, 2018
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Just my 2 cents but I had a similar problem. A rattling noise that sounded like it was coming from the engine but turned out to be the front reflector rattling on its mount. Might be worth checking out. I try to start with the simplest things first before you go ripping apart the motor. Also make sure it's not the piston hitting the head or spark plug. If the piston is just barely hitting the head in just the most microscopic way it can cause a rattling sound as well
 

LastFreedom

New Member
Jun 17, 2017
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I believe I've tightened and locktite'd everything possible. It still makes the sound when the clutch is pulled as well.
 

crassius

Well-Known Member
Sep 30, 2012
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OK, if you have no mechanic's stethoscope, you can old school it by locking clutch while running and using a long screwdriver or metal rod held against you ear and then to diff parts of motor to see where it comes from