ATC 250R with exhaust valve?!

[DixiePlowboy]

Today I looked at an '85 R that had another cylinder with what appeared to be a housing for an exhaust valve. It had "HCC" or something close to it on the side of the housing. It didn't seem to have a spacer plate installed under the jug.
Anyone have any idea what it may have come off of? My guess is a CR, but I'm not familiar with them.

[200x Basket]

sounds like a cr power valve motor. there are a couple of companies out there that make the conversion but it is very expensive and has little gain. goto www.macdizzy.com and ask about it.

[brokdown]

sorry if i sound stupid, but later model atc250r's and trx's don't have powervalves? hope i don't get flamed for this lol

[DixiePlowboy]

You're not going to get flamed by me. You're right, the 'R wasn't designed with an exhaust valve. The 'R I speak of has one though.
Re-read my post, and you'll see that the whole message is kind of a "Where did this cylinder come from/it aint supposed to be there?" question.