Hi, Gents – great question about the SAITO crankshaft.
I’ve been using these engines for over twenty-five years and as far as I know, there is no such thing as a reverse rotation crankshaft for the SAITOs.
If you look the mechanics of these engines, you’ll see that the direction of rotation is determined by the relationship between the piston position and direction and the camshaft, the latter rotating at half crankshaft speed. Intake, compression, power, exhaust.
The SAITO incorporates a spur gear on the crankshaft and a twice-size spur gear on the camshaft. By using a special tool to lock the camshaft in position and setting the crankshaft at TDC, the two gears are brought into proper timing mesh when assembled. The cam lobes are machined onto the shaft and therefore not adjustable relative to one another.
There is a way, although not very safe to get the SAITO to run backwards, making marginal power. Let’s say you are running muffler pressure and a uniflow tank. You flip the prop and the engine fires backward. The engine will actually draw fuel from the uniflow vent, through the muffler and into the engine via the exhaust port. The mixture will combust and the hot gases will exit through the carburetor. And yes, it can start a fire – I’ve seen it.
It should be noted that the OS four-stroke engines also have a gear-driven camshaft. The only difference is that it’s driven by crossed helical gears instead of spur gears. Instead of needing a special tool, you simply align a small mark on the exhaust lobe with one of the screw holes in the cam housing.
Want your four-stroke to run backwards? Fear not, it can be done, but only with the ENYA engines! The ENYAs have two separate cams, each with its own drive gear. The intake cam must be rotated 70 degrees clockwise and the exhaust cam rotated 70 degrees anti-clockwise. The engine is now timed to run clockwise, looking from the front.
Have yourself some fun with four-stroke engines. Buy one that suits your needs (I prefer the smaller ones), set it up to your liking and just fly it. My SAITO 30 powered Little Cherokee has over 1000 flights and I’ve done one valve adjustment (when new) and that’s it. Never even changed the plug. Can’t even remember the last time I adjusted the needle valve.