It would have been easy to just part the bad bike out for spares, but a second option also existed: rebuild this engine with a 60cc cylinder kit to replace the bad piston and cylinder, and turn this engine into our high performance motor. FA50 engines are easy to swap so we could keep our original FA50 road worthy, get this engine prepped, and swap it into our old bike. The old, stock engine could then be swapped into the second FA50 and we would end up with two complete bikes and succeed in both of our goals. The only real change to our engine plans here was buying a 60cc engine kit. We originally wanted to keep our FA50 as a 50cc bike, but a 60cc swap would repair the damage inside our second engine. We are refreshing our engine from air filter to exhaust, so let’s run down our new bits from suck, to squish, to bang, to blow.
Air of course has to enter the engine, and with all sorts of plans to increase the amount of air our 60cc engine will be ingesting, we needed a bigger carburetor. Fortunately, we took care of that some time ago with a Mikuni VM-18 carb and MLM intake. Check out our last installment to see the details of our intake installation. These parts would be removed from our old engine and installed onto the new 60cc motor.After the carb, air will see the reed valves. These act like the intake valves of an engine and their size and stiffness will affect power output. They can make a big difference in the performance of the engine, as they have to be able to easily let air in during the intake stroke, but prevent the intake charge from being blown back out the intake port as the piston is in its compression stroke. We picked up a set of Boyesen Dual Stage reeds for the FA50. These have both a soft reed for low end power gains, and a stiffer stage for high RPM power. We also picked up a pair of Super Stock reeds for our old 50cc engine to give it a light power boost when we install it into our second bike. These are a single stage system but are a lighter material so they open more fully to improve airflow.For ignition, we are upgrading to a newer coil. Our new coil fits a handful of different bikes, so it’s not a direct fit, but it’s still quite simple to install. Judging by the condition of the package, this coil is almost as old as the rest of our bike. I would say what brand this coil was, but it was nameless (and probably no longer made either). This should keep spark stable in the FA50. We may also need a colder range spark plug, but we will use the original plug for now then read it later and determine if we need a colder plug.
1 comment
Such a fun project! Looking forward to more