500AF keeps blowing exhaust "O" rings!

[kxpegger]

I bought a KX500AF from Service Honda last year. I get about 4 to 6 rides and the exhaust "O" rings are blown out. It uses an FMF pipe. I've been putting high temp RTV silicone on with the "O" rings and get an extra few rides but the end result is the same. Are there some high temp "O" rings available or some method to keep the "O" rings from blowing out? I've got an "07" RM250 with over 100 hours on the original single "O" ring and it is still holding up well!

[The Flyin Hawaiian]

Are you using the FMF orings? I had similar problems with the FMF stuff and switched to oem orings. It seemed like the FMF orings were slightly undersized. They also seemed to get rock hard sooner.

[kxpegger]

Are you using the FMF orings? I had similar problems with the FMF stuff and switched to oem orings. It seemed like the FMF orings were slightly undersized. They also seemed to get rock hard sooner.

Yes! FMF "O" rings. I believe the high temp rings are orange colored. Why FMF doesn't sell the absolute best "O" ring material possible is beyond me. I think the "O" rings are 55mm for the CR500/KX500AF pipe but not sure what the thickness is supposed to be?

[DoldGuy]

KX Pegger,
A buddy had a CR250 that was very neglected (by him) and actually ovaled out the cylinder exhaust port, which created a substantial area for Cold Air to be sucked in (seized on the exhaust side). He was El Cheapo Guy & I tried to get him going as inexpensive as possible, so I went to Lowes (yep, the Blue Box Store) and matched the orings up with some that were Thicker and it sealed the Exhaust. He had those Orings in that thing for a couple of years & never had any problems (I thought for sure they would get hot and melt) & since then I will not hesitate to go pick up some orings there for an exhaust.

[The Flyin Hawaiian]

There used to be this exhaust tape or wrap that you would wrap around the oring area of the pipe. It was a putty type material. I used to use it on my old 88 500 with good results. I havent seen it lately though.

[gwcrim]

...so I went to Lowes....

Bravo!  I love a cheap easy fix.