Im thinkin most of the hondas were four stroke [img]i/expressions/face-icon-small-sad.gif[/img] I dont think twisting the belts would be very good they wouldnt last very long. I made a racin mower a while back, their rear ends/gear box is crap. I tore it to peices in a few days with the stock hp just geared a lot higher. All i did was weld a rear pully onto a front pulleys mount and vicaversa to change the gear ratio. The limited slip would nearly stop you in a corner then when u went straight again it would wheelie and throw you off. It was a one race deal and i had a can of ether with a string attached on the side of the carb [img]i/expressions/face-icon-small-smile.gif[/img] (engine had bad rings so my dad didnt care) I didnt get to go though because I tore up the rear end playin around. If I were you I would be looking into kits to make it Oil when turned on its side or figure out how they do it for ultra light air craft. I saw one on discovery channel with a 20 hp beefed too 22 hp making a small plane go over 200mph. As for the motor bikes, look on ebay, every now and then somone will put up an RD350 or RD400 thats rusted to pieces and fallen apart, but the engine is sitting in a bucket in perfect shape with like 5k miles. I kinda get the picture that these bikes were kinda scarey so not many people put many miles on them. They were super light and had the power of a banshee, and way way more with just pipes. As for the hondas, my dads friend had one when my dad had an RD350 and he said he out ran him with my Mom on the back and not trying (73 XL350 i think). You just might be able to make that lawnmower engine work though, or if not you could get somones lawnmower that has a broke deck (theyl practically give it to you) and you can end up with a 22hp twin or more!!!. Although they dont really have that much hp, a 22 has more like 17 or 18 they have a boat load of torque. Another Option is a chain drive mower, We had one of them not to long ago, that would make your job SOOO much easier. Hey, that bike though, find out if its two stroke, if it has many miles, what kind of condition it is in etc..... Could be a good buy. If you look really hard though, I think Suzuki or was it kawasaki, anyways one of them made Big Bore 2 stroke air cooled bikes back in the 70's. If you could get one of them cheap......... woah, monster gokart from hades.

 

suzuki had big bore 2 strokes in the mid 70's. they came in three sizes. 380, 550, and 750. i owned a 380 and a 750. the 750 would smoke all my buddies honda 750's. the 380 and 550 were 3 cylinder air cooled engines and the 750 was a three cylinder and water cooled, as a matter of fact the nickname for it was the water bufalo. yes you read it right they were 3 cylinder engines. kawasaki also hat a 500 and a 750 at that time. the suzukis were called G T likein GT 750. in 76 suzuki went to the gs 750 which was a 4 cylinder 4 stroke

 

. i just hate to see this perfectly good engine go to waste. i looked them up and 12hp b&s are around $400. since i had the lawn mower, i ended up with an electric start, lights and all the other stuff. know what i mean? anyway i still need a frame to get an idea of what type of engine i'll need.
where can i find this "side-oiler-thingy"? how would it effect the carb?

 

Look up planetsand.com they always have banshee motors in the classified section of the forums for around $1000.