Hi
If someone would ask me if I would fly behind a Briggs, I would say YES. Can you imagine what people do to these engines in lawn mowers and they keep running. Only problem is, Briggs will not talk to you or sell you parts if they know it is in a plane. Now that is what I have heard, not personal experience.
Bob

Goakin, which I think is a Chinese company, makes a v-twin that has been converted to aviation use. Here is a version with a redrive sold by a company called Subaru Air.

Aeromarine currently offers a 60hp Goakin engine with redrive...

https://www.aeromarine-lsa.com/vtwin/

Hi
It appears to b liquid cooled? Where is the radiator go?

Not a V twin or four stroke but someone was talking about a Single cylinder 400cc 2 stroke arctic cat snowmobile engine on the homebuiltaircraft forum.He was pretty excited about its light weight and power(65 Hp).No idea about the weight.Kevin armstrong from UK has experience with the Gaokin  chinese ATV engine.He has many videos on net using it in a Trike.It uses an ACE aviation redrive.He even crossed the English channel with this engine.I think its based on some Bombardier/Can Am engine.Some further searching revealed that the Aeromarine setup is all derived and based on work done by Kevin Armstrong who being a very nice gentleman shares his experiences with everyone.

I don't think the Culver reduction drive is available from Culver anymore. The brought the prototype to our local WW1 replica fly-in. It was/is an amazing piece of engineering but does require an electric starter. As I  remember, turning the prop does not turn the crankshaft.  

Quoted from joe.scalet

I don't think the Culver reduction drive is available from Culver anymore. The brought the prototype to our local WW1 replica fly-in. It was/is an amazing piece of engineering but does require an electric starter. As I  remember, turning the prop does not turn the crankshaft.  

I think if one can source the Rubber Balls per specification then the reduction itself is no big deal.Gene smith says in one of his interviews that the setup is not a clutch so the prop doesnt free wheel.

It was not a clutch but allowed the prop to free wheel between the power pulses. The system functioned as a part cycle one way clutch so the prop inertia did not feed back to the crankshaft.

It was not a clutch but allowed the prop to free wheel between the power pulses. The system functioned as a part cycle one way clutch so the prop inertia did not feed back to the crankshaft.