Setting a Land Speed Record: Preparation (Part 2) - Engine and Drivetrain

The next major step to getting the bike legalized was upgrading the engine and drivetrain to meet tech inspection requirements. Originally, I used the exhaust system that was supplied by the manufacturer. However, their design, a small rectangular muffler bolted to the cylinder head, directed the exhaust forward and towards the ground, and was extremely restrictive.

Figure 1 - The original exhaust is visible below the fuel tank.

Using several pieces of pre-bent wiring conduit, I had a straight-pipe exhaust system welded up at a local shop. I compared the bike's performance before and after the exhaust was changed, and there was a significant increase in power with the free-flow, non baffled exhaust that I installed.

Figure 2 - New Exhaust System

The next major hurdle was to upgrade the clutch and construct its protective housing . The model of centrifugal clutch that I installed needs to be manually lubricated regularly to prevent the bearing from seizing. However, because my motorcycle is much heavier than the minibikes it was intended for, it tends to overheat much more quickly. I solved this problem by drilling holes through the crankshaft retaining bolt and the side of the crankshaft, installing a grease fitting, and filling any remaining gaps with packing to prevent excess lubrication from fouling the clutch shoes. This allowed me to externally inject grease into the clutch bearing without disassembly. I also machined cooling holes and ribs into the clutch cup to increase the surface area and aid heat dissipation.

Figure 3 - Improved clutch cooling

I also installed a new, more reliable throttle cable and a heavy-duty aluminum chain guard to protect against breakages.

Editor's Note: Did you miss Part 1 of this series? No problem! Just click here.