I have this same question posted in the Honda forum:

Will a silencer for a TRX250R fit an ATC250R (85-86)? Also, does anyone know what the website is for Eddie Sanders Racing. I think I saw an address in his ads a while back, but I don't have any of my mags here in Korea.

 

www.esr250.com is ESR's site, it seems to have been up and down lately.

 

I have trx silencer I use on atc. Its a quiet silencer from lrd. It mounts. It seems like I had to use the grab bar hole. Its not on now but it works.

 

I too run a TRX silencer on my 250 (DG) mounted to the forward most hole on the grab bar.