So about a month ago I decide to buy a mini bike to mess around with. It's a Kenbar MB-6 and was manufactured for only a couple years (2000-2004) before being bought out by another company (chinese). I know the forks have been bent really bad but it doesn't really effect the handling too much. The previous owner must have hit a wall or something, lol!
It has a OHV Tecumseh 6hp horizontal shaft engine called the OHH-60 and has a torque converter called a TAV-30. I had freshened up the engine with new piston and rings since the bore was still within spec, replaced both valves and springs (exhaust spring was significantly out of spec). I also dumped the emissions primer bulb type carb for a fully adjustable one. I did some head porting to clean up the casting marks and change the angle at which the fuel flows as there is an extreme 90 degree angle entering and exiting the combustion chamber. I also lapped the new valves to the seats.
The TAV-30 Torque converter was fully disassembled and properly cleaned. I had to wet sand all of the surfaces that the centrifugal weights swung out on since there was signs of pitting through the zinc coating on the back sides of the pulleys. I also drilled a 4th hole to put more preload on the driven pulley clutch so that it engages a tad later and lets the engine rev out a little more between the two engagement points.
I hooked up a switched headlight and tail light since the engine comes from the factory with a lighting coil and she is super bright out front!!! On the main front frame I mounted a tach since I removed the governor and need to ensure I don't over rev to the point that the stock rod fails. I am still unsure why it won't pull farther than 3350 rpms so if anyone has any ideas please respond here or message me. It had this issue before the rebuild too and I thought for sure it had something to do with the valves and springs. This engine has a composite cam believe it or not so I was a little weary on going with heavier springs in fear that it would be too much for the cam and damage it. I would like to at least 5000 rpm out of this engine when I'm done. It has an iron flywheel so I am not too worried about it exploding at those revs. Maybe lapping the flywheel to the crank and advancing the timing would benefit a higher rpm???
I did ride this mini bike on a closed road where there would be no other vehicles around and be safer than on a high traffic street. The whole are has yet to be developed so people aren't even living too close, but there are a few that like to ride their bicycles as seen in the video.
