I had 4 engine failures with a Cuyuna 442 in fifty flyimg hours, and 10
engine failures with Rotax 447 in the next 200 hours. The reasons didn't
always have to do with 'reliability'; causes included fuel problems,
clogged filter, broken electrical wire, etc. The point is, with 2-strokes,
you have to fly with your brain in gear at all times.

Cuyuna aircraft engine service manual 1980 - 1995 2SI. Cuyuna 2SI service repair manual ultralight aircraft engine. This CD contains the following manual for the Cuyuna 2 SI UL engines: Cuyuna 2SI service repair manual for the UL-430 UL339 UL-215 ULII-02 series engines. Covers every area of repair, light to heavy, full specs, troubleshooting, testing, rebuilding, fully illustrated. Parts manual for 230- 808. Plus watercraft engine parts and info.

The old Cuyuna 442 had problems with cooling because the air blew straight
back through both cylinders, so the back one didn't get cooled as well. We
solved that by simply tuning it so that it wasn't running on the edge of a
meltdown. Also, the 442 was beefier and hence heavier than the Rotax.

Cuyuna 430 Service Manual Transmission

The real problem was the old ignition timing, which was impossible to set
right. Electronic ignition should have completely cured that. Cuyuna also
used a Mikuni carb, vs a Bing for the Rotax. There were more arguments
about the relative merits of the carbs than of the engines. The carb is
REAL important.

I'm not familiar with how the Cuyuna has evolved, but AMW looks like it is
comitted to it.

Cuyuna Engine Forums