Hello and welcome.
Let's introduce you to the new triple two stroke engine.
I always dreamed about designing and building a two stroke engine using moped parts and homemade parts. Wouldn't start with the 4t V3 engine, because I could easier modified this engine for serious usage.
Being a Yamaha RD 250 owner, last year busy with tuning and modifying the bike (still needs some work
). Lastly I have make a new set of expansion pipes that turned out well. That taste like more, in the form of, let's make a homemade two stroke engine!
As said, being a Yamaha guy. I was looking for moped parts of that brand. Beside outboard motors, there aren't Yamaha triples as far I know (air cooled).
I know that my dad had owned, before he had a RD motorcycle, a Yamaha FS1.
There are nowadays still aftermarket parts. Other option was RD/DT 50. But I saw that the cylinder sizes are quit larger than the FS1 ones (40mm each).
The FS1 produce stock horsepower of 4.8 hp at 9000 rpm. Multiply that with 3 that sounds sweet, same as the exhaust note it produce! Could power a air or water propeller?!
So the SPE (own named branch) FS3.
40 mm bore 39.7 mm stroke make it 150cc total.
Fitted with RD/DT50 16 mm Mikuni imitation carbs and reed valves. Using the FS1 carbs is not a great idea. The FS1 was build as rotary valve inlet or membrane. There for the carb is fitted axial to the crankcase and behind the crankcase cover. So there is no air hose connection for a air filter.
So the carbs and membranes need to fit on the crankcase rater than the barrels. And the cool fins of the barrels and heads are vertical. I decided to place the cylinders horizontally. Later as upgrade I could make a forced air cooling sheetmetal like a 2CV or using the air propeller and mike it a aircraft look-a-like engine. Other idea to make watercooled heads if I want to use the engine as powerplant for something in the water (!)
So far. Making a crankshaft out of multiple pieces. Would be challenging to make it straight and true. Then building a crankcase around it. As you see the crank would be quit large and heavy. Yes, she would be not light. I've been looking to make the crank cheeks thinner. But this resulted from a crankcase of 4 extra parts. The crankcase must follow the shape of the crankshaft with bearings and seals.
So the crankshaft is more the flywheel 1-one and the disc at the front would be more the trigger wheel to fit the 3 or 4 magnets for the ignition. So the trigger wheel / flywheel could be made of aluminium.
I have made a motion video of the engine.
Last pictures shows the materials and first parts of the crankshaft.