KX500 COMPRESSION LOSS

[monster malibu]

Hey guys, I just started riding the other day and noticed my bike was running kind of differently ( low on power at times). I came to a stop and my bike stalled and wouldn't start again. I felt the radiators and they were warm, I then felt the jug and It was smokin hot, but would still roll over. After setting for a few hours the bike rolled over real easy "by hand". I didn't think to check the coolant level before riding. I haven't had time check the compression yet. Can somone tell me what it should be at? I was thinking around 125lbs. would be ok to run on. Anybody run into this problem before? Bob.

[Hillclimb#42]

 Plenty of times. Seen and done it. If you run it too lean or just run it forever or any mild catastrophe happens you lose compression. Usually the rings are toast. Hopefully you re lucky enough to be buying some rings and a piston plus the gaskets. You won't know until you pull it apart and inspect cylinder and ports. Quick check piston by pulling exhaust off and rotate around slowly with kicker. Inspect rings and piston skirt. Should look new, not like you were dragging it behind your truck down the interstate!!! If they look good, it could still be a hole in piston or somethin, you kinda are hoping for mild damage to rings. Should be tough to kick thru without standing on it. Jug would be very hot, anyways, but no kick compression has to be worn rings for one reason or another.

[monster malibu]

 If the piston and jug looks ok will I be able to put a new ring on and go? Where do I order a piston and ring for my 87? I've checked Dennis Kirk, Rocky Mountain, MotoSport, and Bob's cycle supply for a new piston and ring for my 87 and they only list 88-up. Will the 88-up piston with two rings fit my 87?

[BigGreenMachine]

88-04 piston kit will work in your 87.

[fluffy]

try bike bandit for parts,also they give a discount for ama members

[hughes]

If the piston and jug looks ok will I be able to put a new ring on and go? Where do I order a piston and ring for my 87? I've checked Dennis Kirk, Rocky Mountain, MotoSport, and Bob's cycle supply for a new piston and ring for my 87 and they only list 88-up. Will the 88-up piston with two rings fit my 87?

88-04 piston and rings work great. Same piston kaw just added a second ring to the newer piston. wrist pin and bearing are the same so are the circlips. Sounds like you stuck a piston if it stalled and you could not crank it over but after it cooled down it cranks over.

[monster malibu]

Thanks for the info guys. Hey hughes I think you miss understood me. When the bike stalled I was able to roll the motor over easily by hand, I forgot to check the coolant. 

[monster malibu]

Well I finally checked my bikes compression today and it was 55lbs. I checked it 3 times and all the readings were the same. Time to tear off the top end, hopefully the jug and head is ok.

[hughes]

That sucks. Keep us posted.

[monster malibu]

I "finally" got the topend off my bike and the piston was bad. The previous owner said I shouldv'e rejetted after adding the Moose torque spacer, he said it was running lean. The cylinder has a little aluminum in it, I was told to clean it up with some muric acid. The new piston is on the way and I can't wait to ride!!

[monster malibu]

I FINALLY GOT MY BIKE BACK TOGETHER!!!! Thanks for the dual ring piston swap info guys, the new wiseco fit perfectly. I got a Clymer repair manual for my bike and got the KIPS exhaust valves in the right position for reassembly and it fired right up. I got up today excited to ride and it's raining, I AM NOT HAPPY!!! Thanks again guys, Bob.

[Johnniespeed]

 Hi MM
  You mentioned that the previous owner said to rejet when adding the Moose spacer.  I added a spacer to mine, and did not change jet.  The mixture did not change on mine, but what did happen is that the power seems to be moved to a lower RPM .
     In my opinion the spacer did not cause your meltdown. I would however be real concerned about having the jetting right and about not having any intake boot or crank seal leaks. On a red bike of mine, I had piston meltdown after a corner broke off a reed.
    I am hoping you will find the source of meltdown before you loose another piston.
   John

[monster malibu]

Do you think the melt down couldv'e been caused by a overheat problem? When I pulled the coolant line off the water pump to start the tear down, I only got about a half a cup of water/coolant to come out.