I upgraded my 912ULS with Hal Stockton who offers a very high quality big bore kit.

Several folks on the forum have also upgraded their engines and I have never heard a bad word about Jay (his partner) or Hal. They are just the best and stand behind their products.

My engine is now rated at 114 Hp continuous. When you consider that a 912ULS is really a 95 HP continuous engine, it's a pretty substantial upgrade. And, you can really tell the difference.

I think Hal also has a cam now that adds a little more HP, but you have to split the case to install it.

My 114 engine was new cylinders and new pistons. They have more cooling fins on them and are really high quality. Basically, bolt on more HP.

If you decide to go with the Rotax and want a little more HP, you might consider getting an upgrade from Hal.

Regards
Rodney