New to the forum. I purchased an Airbike kit that is basically un started. I had kicked around the idea of the Rotax 503, but starting to lean more towards buying a new Hirth F23. Definitely more money up front but maybe not so much in the long run. Does anyone on the forum have any input on the performance of this engine and any install details for the Airbike?
Thanks! Mac

Two Quicksilver ultralights at my airport have the F23.
It is a very smooth running engine and known to be reliable.
It is also expensive and hard to get, might take 1-6 months to get one once you order it.

I just replaced the Hirth F33 on my MiniMax.
Nearly ordered a F23 but it would have taken a lot of work to mount it on my airframe. An inline twin cylinder like the Hirth 2702 or Kawasaki 440a was a better fit, ended up getting the Kawasaki and love it!

I've never seen an AirBike in person but from pictures I've seen it looks like the F23 would be a great fit. Hopefully someone with more AirBike knowledge will chime in.

If you get the F23 only your wallet and possibly your spouse will be disappointed with the decision.

Thanks for the replies! Looks like a good choice for the Airbike. Seems like the high initial cost is about the only negative.

I have Jeff's old plane with the F-23.  He changed the exhaust to a much better solution, and it was funny to see the original low hanging mufflers in those pictures.  I've only had it a couple months, and have been doing more working on it than flying it.  I wanted to replace the panel, wiring, hoses, and move the engine back some for CG.  No pics until I'm done though, maybe a week or two.  

Rusty

Greetings,

I have the new engine mount in place, and I'll attach a few pics.  To move the engine back as far as possible, I had to hunt down some 45 degree carb flanges.  The mount is machined to allow the Barry mounts to fit directly on the engine case bolts, then the mount attaches to the usual square tube.  

I don't have any performance figures, but climb seems pretty lackluster.  I will be working to measure and verify the climb very soon.  

Rusty