im making an ultra spadstick for a friend and he has given me a weedeater with a ryobi 28cc engine on it.

is this a good conversion engine? its only 3 cc below the normal ryobi so shouldnt it work fine? im hoping it has the power to haul the plane around.

anyone?

My brother has a late model, (with the "smog?" slots in the cylinder) Ryobi 31cc on his Ryan's Rebel. Stock carb that has been "massaged" slightly larger, muffler gutted and provided with a larger outlet. Besides that, no other mods other than the conversion to aircraft use. It turns an APC 18 X 6 wide blade prop at 7500 rpms, and flies the 80" span, 13.5 lb. Ryan's Rebel quite well. It won't do "3D", but it WILL loop from level flight at half throttle.

So... Take it from there. Nobody wants to recommend something and be blamed later for their advice if it doesn't perform to your expectations.

Good luck and have fun,
AV8TOR

if it doesn't do well, on a stick type plane with a ryobi, it's about a half hour job to throw a 31cc piston/jug on the 28cc, and if it needs more power to weight ratio, remove the flywheel and coil and run gas/glow, readjust COG from there...

i had planned on going gas/glow with this engine for purposes of weight removal.

i understand your concern av8tor and i respect your opinion. i think i will just have to give it a try and see what happens.

how easy is it to get ahold of a 31cc piston/jug and will it work with the crankshaft?

every other engine manufacturer that made multiple sizes with a same design used the same crankshaft and crankcase so I would assume so. the McCulloch 28/32 use a common crank and crankcase, the poulan featherlite 18cc, 21cc, 24cc and 25cc use the same crank and crankcase, and a few of the echo's have common parts.