durabol wrote:
Thanks for the responses.

-I planned to have one carburetor (and crankcase) for both cylinders.

-I have access to a lathe and a milling machine but I don't have that
much experience with them so I'll have to learn as I go or get someone
else to do the machining

-I do plan to build the engine in a modular way so I suppose I could
add more cylinders.

-I do have some experience with lost wax casting although not with
much success. The engine casting that I had envisioned may be too
complicated for the simple gravity casting techniques I was planning.
I also worry about hot tears of the cylinder as the aluminium cools
and casting decent heat fins.

-For the cylinder I was planning on just an aluminium wall since I
have heard "cheap" lawn mower engine can get 500h on them. I though
that the bearings in the engine will probably need to be replaced in a
few hundred hours anyways, so the bore could be resized then.

With some pretty fancy metallurgy you can use an aluminum cylinder wall.
It's how the Chevy Vega was done, and it worked great -- except when
it didn't.

There are other treatments that'll let you run a 'plain' aluminum
cylinder -- but none of them are simple, that I know of.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com