RM100 making weird sound...

RMshift03

Member
Aug 23, 2006
12
0
About 3 weekends ago I went riding and my '03 RM100 started making a really weird sound. I got messed up over roots in the beginning and dropped the bike pretty hard over some rocks but I'm pretty sure it wasn't making the sound yet.

Then I had the bike pinned wide open for a couple of seconds and smelt what seemed like burning oil, which stopped right away and didn't happen again (I didn't go WOT again). I let off and it wasn't until I was back on the trails that i noticed it was making this deep, low, and yet whiny sound, espically when I let off the gas. It almost sounds like a 4-stroke when it's coming back down to low revs. It's hard to explain but it's pretty distinct in the sound, all the time.

My dad and I took the bike apart to check the pistion and rings which were find. We're not seeing any cracks in the pipe and we repacked the silencer. Nothing is loose, the compression is fine. The bike runs fine, also.

I went riding again the weekend after that, almost as a test ride but it's so distracting that it wasn't fun. I've taken the bike behind my house to ride and check it out but it still is running as well as it ever did, but this sound is getting louder.

I know my description of the sound sucks but does anyone have any other ideas what may be causing this? Thanks for any input...
 

racerx090

Member
Apr 18, 2006
16
0
Same thing happened to my 2k3 KX250 as soon as I purchased. After months of riding there have been no ill effects and the bike runs like brand new. I wouldn't worry about it if I were you. You get used to the sound. But maybe it was just my top end breaking in. My sound sort of sounded like a sucking sound or a blower or something windy.
 

1989kx250

Member
Mar 17, 2006
63
0
my 1989 kx 250 makes the same type of sound, i had just replaced the bottom and top end, i was told the new bearings make the whiney sound, or that the intake makes the sound, and that its not a problem and if its the bearings, should go away after 5-10 hours of riding time on the motor.
 

RMshift03

Member
Aug 23, 2006
12
0
Guess I had put this in the wrong section at first, sorry.

We ordered a new pistion for the hell of it a few days ago, but I'll just keep using it then. I might be selling the bike soon though, and that might make it tough. Oh well...

Thanks for the help.
 

motometal

LIFETIME SPONSOR
Sep 3, 2001
2,680
3
when you have it apart, take a look at the power valve. Make sure everything is in order, and the valve can't touch the piston. If this was it, it should have lost compression a long time ago anyway, but worth checking. Some of the KX motors had problems with the power valves, and I believe this is really just a KX100 motor.
 
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