rattling and vibration from motor??

[TrackMaster]

my 96 yz125 is making a loud rattling sound when revved. When it idles it sounds fine, but above 1/2 throttle it rattles and vibrates really bad. Last ride i got armpump really bad and started noticing it vibrating. It is getting progressively worse, and has vibrated my axle nut, sprocket nuts, and pipe mounts loose!

I understand 2 strokes vibrate, but it is getting worse and worse and the rattling sounded like the pipe was loose. After new exhaust orings, tighter springs, and new mounts it still rattles.

The clutch looks fine, it only has 10 hours tops on new crank bearings, new rod, and lower rod bearing. My only ideas are the wrist pin bearing could be shot, and the clutch hub bearing moves just slightly, but seems like normal "play" in a bearing.

 

[David Trustrum]

Well it could be several things, but my gut instinct is saying the crankweb has rotated slightly due to a loose web vs BE pin.

Possibly a bearing has started to fail. Hmm. . . nah.

Try the simple first. Inspect the flywheel is okay, then grab & wiggle it to check LHS main bearing.

Check you engine mounts aren’t loose/sloppy & frame for cracks.

I wouldn't want to run it much longer without resolution.

 

[TrackMaster]

I found the problem, only after playing with pipe springs/orings, tearing down the clutch, inspecting the flywheel, and pulling the top end. Of course it was none of these things, only a loose motor mount. :o doh!

thanks for replying

 

[David Trustrum]

Hey better to find it than find there is a real expensive problem. This way you have done your top end inspection for a while.