There is an engine on ebay that I'm considering.  It was pointed out the other day to someone considering a track bike, but my search-fu is weak and I can't find the thread. 

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1,1&item=4642747223&sspagename=STRK%3AMEWA%3AIT

Pros: I'm in AR this week (no shipping cost besides gas) and it has quite a few extras besides the engine.

Cons: It's a little pricey and I don't really need the engine.

Nobody has bid on it yet, but it doesn't seem too bad.  $375 seems pricey, but it has carbs and a tach.  So should I try to get it, or should I save my money?

I'm always very cautious, but I'd buy it.

Here's what I would do:
Buy it and rebuild it, and mean the whole thing, maybe even go to town and do a port and polish, cams if you can find em and all.
Then pop the super hot 500 into my bike and pull mine,
Wash, rinse, repeat.

Keep a spare for a bad day, LOL. If I had enough I would so do it.

Man Egaeus, if you didn't live so far away I would LOVE to come help you with your projects. Rebuilding engines and what not sounds like a blast!! 

i'd do it if i had the cash ! i'd go for it . but  seeing how its out of the bike already i'd find a local shop or send it off and have the heads ported and polished  and bored get it to at least 500cc's but me being me i'd want it to 555 but eather way i'd bore it and then have it ported and polsihed slap it in the bike (after you get everything ealse cleaned and made sure theres nothing wrong )  then stick it in your current running bike . when you that motor out do the same to it . have it set up the same way or maybe a little diffrent . that way if somthing ever happens to the other one you have one to have ready to be put in it   its a never ending process .. you would never be left with out a motor

make great fun for a go cart

Well, I didn't buy it, as I'm sure is obvious if you click the link.  He didn't answer my questions (e.g. how long has it been sitting?  Can I inspect it before buying?).  I gave him my email address if he's still interested in selling it.  I'm not going to pay that much for it without an inspection.  I'd still like to get it, but I don't want a completely rusted piece of crap to start with.