Water cooled YZ490 barrel

[zorroz]

Looks like a home made effort:

http://cgi.ebay.com.au/YZ-IT-490-465-WATER-COOLED-HEAD-AND-BARREL_W0QQitemZ270376315200QQihZ017QQcategoryZ35233QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[Marc.com]

teas maid, what were those things that you used to go camping with and you could drop burning wood down the bore and make a nice cuppa. 
In this case you just drop a pinging YZ 490 piston down the bore.

[LWC82PE]

i head about that one a while back, im pretty sure its off a formula 500 speedway car running a YZ 490. i rebuilt a different YZ490 speedway engine last year but that had a aftermarket Smythco water cooled head but still had the air cooled barrel.  A guy called in yesterday who used to race speedway and said that the YZ490's were common.