Suzuki FA50 Engine & Gearbox

Squirrel Power: Making a Minibear Part 2

Our 1982 Suzuki FA50 is a pretty fun little machine.  It turns heads and is a great little around-town runabout, perfect for parts store runs and other short errands.  However, the age of our bike is showing.  Our top speed is a paltry 25 MPH.  This may have been fine in 1982 but in 2020, with inattentive SUV drivers texting and driving, we need more power to keep ourselves out of trouble.  Oddly enough, more power would not have saved us from this collision (though the upgraded brakes and tires we installed many years ago allowed us to stop enough from getting badly hurt).  A bit more oomph will allow us to ride to different parts of town (up till now, we’ve dared not go anywhere that has a speed limit over 30). 

Fortunately, the FA50 has become somewhat popular in the last few years and there are some go-fast goodies we can buy to bump up our power output.  There are a few other tricks we can apply to improve power and speed in both the engine and transmission.  So we decided to do a full top to bottom rebuild on our FA50’s 40 year old engine to give us enough horsepower to handle this modern world.

FA50 Pair
Before we tell you how we built our engine, let’s rewind to winter 2018 where I spotted another cheap FA50 on Craigslist. This is a great story about why it’s a terrible idea to buy vehicles in the rain. We were expecting a clean, low mile bike with a lot of cool, rare goodies like a windshield, splash guard, and cargo box. While the bike only had 300 miles and did indeed come with all of those options, it had been stored outside for a number of years and was badly maintained. The ignition key had been lost so the owner broke the ignition barrel. The cargo box and splash guard were also broken, and the starter was broken.
2nd FA50 Disassembly
We should have pushed back on the price or walked away but it was absolutely pouring with rain when we arrived and we didn’t do a good job of inspecting the bike before paying for it. We still planned to fix up and re-sell this bike but the amount of money and work needed to turn it around would be a lot higher than expected. Since we had the bike, we went ahead and dismantled it to see why it had stopped running. Pulling the engine only takes an hour: drain the oil and fuel tanks, unplug the lines, unplug the magneto and spark plug, unhook the throttle and choke cables, then remove the two big bolts that secure the engine to the frame. We also removed the shock, rear wheel, and kickstand to make disassembly easier.
FA50 Engine Damage
When we stripped the engine we found out why it wasn’t starting. Either the engine had ingested something or the piston seized in the sleeve and gouged the hell out of the piston and cylinder. Our money is on debris as the previous owners had removed the air filter. This engine would no longer be a quick fix using spares we had lying around.
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