If you act fast it can be yours now for $775
I have no affiliation with this.... but OMG 
http://sfbay.craigslist.org/sby/mcy/1636801456.html
insane wheelbarrow builder said: Because of various habits (!) and other abilities (wrenching) I bought a used RZ500 4-cylinder 2-Stroke engine, built a mount jig for it and then tuned the crap out of it, it is running STRONG. And owing to various habits I have (thankfully) put behind me, at the time it seemed like the right time to mount the RZ500 motor onto a wheelbarrow I wanted to use to clear my land in Gilroy here of brush/weeds/etc. Thing is, a lot of the clearing is down in a low part of the lot and it was impossible to carry enough of the clearage by hand in a timely fashion, so...I bought the biggest damn wheelbarrow I could find and rigged up a chain drive for its wheel and motor mount for the RZ500 engine. It is now ready for the track. The right hand grip of the wheelbarrow has a 1/4 turn throttle, and the front wheel of the barrow has a disc brake and the brake lever's on the right grip too. The left handle of the barrow has the clutch lever (yes the gears run through, but you can't run fast enough to keep up). What I do when I reach ground level is throw on my rollerblade skates and run this sucker down my driveway to the street to drop off the load of clearage for the 'yard waste' service to pick up. Probably done about 60mph, but got scared. The barrow got my custom Yellow with black-and-white stripes just like the factory Yamaha roadracers. It looks fine. I have used it only about 10 times -- the problem (come to find out) is the chain drive cannot be geared high enough to prevent burning the tire off the barrow pretty damn fast. I only got 10 runs out of the RZ500 motor on this huge barrow and the barrow's tire needs replacing. Burns rubber all the way down the driveway. I will say this -- it is a fricken-stricken THRILL running my barrow down my long driveway, being pulled by a 100+ hp 4-cyclinder 2-stroke motor -- just trying to hang on to the barrow, nearly pull my arms out the socket. Then I've got it piled HIGH with wet clearage (weeds etc) and the 2nd job is -- hanging on for dear life AND not letting the damn thing flip or tip at 60mph. It is a GILROY THRILL. What else is there to do around here I'd like to ask. But, damn thing has TOO MUCH POWER. Enough to allow me to clear the low part of the lot in 1/10 the amount of time. But no wheelbarrow tire will ever win against a highy tuned RZ500 motor (I also tune kart engines, I know how to make 'em scream, this RZ500 motor is a monster). And besides the tire issue, this motor is too loud for my dogs and for me. $775 and you take the barrow too. There are 4 homemade chambers on the motor, had to shorten them to fit on the barrow. NO I WILL NOT PART IT OUT YOU HAVE TO TAKE THE BARROW WITH THE RZ500 MOTOR MOUNTED AND GO. AND IF YOU SNICKER WHEN YOU SEE IT, deal's off. This will come in handy if you can solve the tire problem. Or I was thinking 'do a Parade' but again the motor rips that wheelbarrow rubber right off now. Will try to borrow a digital camera and post pics tomorrow. Only concern there is might scare off some folks who have never seen a factory race barrow. Email.
Edit: corrected the price...
