Has anyone converted a Tecumseh TC200 or TC300 engine? Are they easily converted?

Jeff

No experience with that engine for me. I did have a Tecumseh 48cc two stroke engine off a mini rototiller that I was thinking about converting. I imagine for that application it was designed for a lot of torque and probably would have been best for largish props. However, I ended up needing the rototiller so I put the engine back on the machine and never converted it. It runs very well on the rototiller.

AV8TOR

The TC200 (33 cc) engine has a very long stroke (1.4375 bore X 2.250 stroke), wonder if it would have lots of torque.

Jeff

Many people think a long stroke provides more torque, but I have read numerous times that the increased pressure from a large bore piston would equal out the leverage advantage of a longer stroke crank, all else being equal. Effectively, they both should make about the same torque. A shorter stroke engine is better suited to high rpms because it reduces piston speed and friction. A larger bore allows for larger valves, less shrouding of the valves and better breathing for a four stroke engine, and for a two stroke engine a larger bore provides more available porting area. All this means more power potential on a larger bore engine, as well as being lighter.

Normally, full size aircraft engines are of a big bore and short stroke design, as this makes not only the most compact engine, but also the lightest engine. Most modern full size aircraft engines are of the short stroke/large bore design, and they only turn around 2,700 rpms or so. That kind of "takes the wind" out of the "long stroke makes more torque" argument...

AV8TOR

I have an old Model Airplane News magazine from October 1986. On the back cover O.S. had an add for a new long stroke .61. They said in the add the advantages were higher torque to spin larger props. The ad didn't list the bore diameter or stroke length.

Jeff

It would be very interesting to see a dyno comparison of two identical engines, but with differing bores and strokes.

AV8TOR

I found more info pertaining to stroke in a Banks-Maxwell propeller catalog from 1974 (B-M made props for airboats, gyrocopters, hovercraft, etc). Page 25 (this section dealt with 2-stroke snowmobile engines), "The older long stroke engines were better for use with a propeller than the later engines because of their longer stroke".

Jeff