I am running one of their 330 Pro-X cylinders on my '85 ATC 250r. I had a pretty stout FTZ ported motor in it before but this 330 is a whole new level. ChrisD is running a 250cc FTZ motor and the only difference in our bikes now is that I have the ESR 330 cylinder and head, EVERYTHING else is the same and out on the ice my trike pulled away from his but HARD!! His trike is way fast but that ESR kit is nuts. I wish I'd have sprung for the stroker crank and gone 370cc, maybe next time. ESR does make a pipe for the ATC and from what I hear it is pretty nice too.
John
1985 Eddie Sanders ATC330r
1986 Monstecate
1984 ATC70 (awaiting 125cc transplant)
1984 ATC125M
1986 GSXR 750 - Keepin' it old school!
1999 Arctic Cat 500 4x4 plow machine
1999 Arctic Cat Thundercat 1000 (lake lizard)
1996 Arctic Cat Jag 440 L/C (ditch banger)