Maintenance & Technical > KX500 Original
rattle from motor
RM_Rider14:
Had the same thing. I have had this rattle on many different brands/models of 2-strokes. 99% of the time it's the two stupid 50mm rubber o-ring gaskets that go on the head pipe where it attaches to the cylinder. I just put two new ones (and the copper crush washer/gasket thingy, may not see it, it gets flattened out) on my FMF pipe and the rattle is 100% gone now ;-) Many people when they put an aftermarket pipe on forget to take these o-rings off the stock pipe and transfer them to the new pipe before putting it on the bike. They also wear out and break every two years or so. Take your head pipe off and see if yours are bad, or if they're even there for that matter.
If you need to order them, part numbers;
50mm O-ring = 671E2550 (You need 2 of these)
Copper gasket = 11009-1949 (Only need one)
It's amazing these three little pieces made the bike rattle free, and quiet ;-)
Let me know what your outcome is....
Friar-Tuck:
I went back and read through the responses and apologize for not understanding.
The KIPS sound is like a deep Diesel engine sound.
The exhaust rattle is a higher pitched sound. If you find the exhaust is the rattle your hearing, High temp RTV spread around the pipe sealing surface and wait 24hrs. before you ride.
That will eliminate the free movement or rattle in the pipe. The downside is I don't know for sure if it's worse on the pipe mounts or not. I have not had any problems so far, however I did add some rubber to the pipe mounts trying to isolate some of the vibration but "your mileage may vary"
You can replace the o'rings and crush washer more often and still keep the "free play"
Just something else to consider....
Tuck\o/
matzilla:
The rattle is more than likely your KIPS valves muving vertically in their little spots. Mine does this also. Very normal for these bikes. They move just enough to annoy or embarass you. Not a problem though.
ID KX500:
--- Quote from: matzilla on February 28, 2010, 05:19:36 AM ---The rattle is more than likely your KIPS valves muving vertically in their little spots. Mine does this also. Very normal for these bikes. They move just enough to annoy or embarass you. Not a problem though.
--- End quote ---
:-o I've had too many K5s to think it was bad,,,,good to know what it is,,,,,I thought it was the computer re-booting. :-D
Polar-Bus:
--- Quote from: stroke.n.smoke on February 27, 2010, 12:24:22 PM ---A couple years ago I rebuilt my motor because it had a loud rattle at idle. The bike still has the rattle at idle and its been two years. It did need a rebuild as the crank bearings were not very smooth and the cylinder plating was peeled. I got the cylinder replated and rebuilt the crank. Do these bikes have a rattle at idle normally, once you rev it up slightly the rattle is none existant, but still worries me somewhat. I am going to tear off the top end in the next couple months and have a look. I rode with Snoopjon last fall and his bike rattles too, he figured his was louder than mine and I thought mine was louder but whatever, they both rattled. Mine has a new motor. Is this gear noise from the primary gears? Or piston slap or bearing noise. You can really hear it on video with the helmet cam, but like I said, it goes away quickly once revved up. I had an old IT 465 that was this way too. The motor runs strong still after two years and everyone says to not worry about it, but I do somewhat. Mabye there is too much piston clearance, I used a wiseco and Max power replated the cylinder and fitted the piston. I never actually measured anything before putting the motor back together, just trusted them... I have run Amsoil Dominator oil at 40:1 for the last 4-5 years with zero issues but that rattle is annoying me to the point of another rebuild or something. I have run everything from VP C12 and VP111 to pump gas and even Av gas with blends and octane boost/pump. I have basically settled with AvGas LL100 octane (cheapest high octane) with 40:1 oil mixture. Bike has run great. I guess I will see what it looks like in a couple weeks when I tear it down, but if anyone has any ideas I would like to remedy the rattle while its apart. I will be measuring up the piston and cylinder and checking the runout and crank clearances.
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Also make sure you have the exhaust pipe o-rings and a good copper exhaust gasket (I like to use 2 gaskets) . 250/500cc KX's exhaust header pipes often vibrate against the inside bore of the cylinder.
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