Well to correct a few things, its a cuyuna 430 (430 cc) with different sub designations if it was a pull or push setup. Back in 1983 or so they came up with less fins on the front head to take less heat away so as to balance the forced cooling front-to-back. With two carbs you can have a slightly richer mixture on the rear cylinder to cool it a. Cuyuna / 2SI aircraft engine service manual 1980 - early 1995 2SI. 215 thru 808, includes the 460 430 UL2-02 and others. Bookmarked, indexed 103 pages File Data This file is sold by aircraftmanuals, an independent seller on Tradebit.

Cuyuna Engine Forums

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.

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 Engine

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.

Cuyuna Engine Company

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

Cuyuna 430 Service Manual User