Question for you that have installed the 3 cylinder yamaha.
What gear ratio and gearbox are you using, what prop are you using and what is the distance from your mast to the prop flange.
I am looking to install one in a RAF2000 and would love to chat with someone that has done this mod in their RAF.
The Sport Copter I have the Yamaha three banger on uses the Rotax "C" gear box @ a 3:1 GB ratio. It is the standard "Todd Rieck" conversion running the RK-400 clutch improved upon by Todd.
Currently using a 68" Sport Prop (plan on replacing that w/ a Warp Drive that would be tougher for those little rocks/runway debris that get sucked up into the leading edges).
Sorry, but don't know the mast to prop flange distance until the next time I venture out too the hangar.
Haven't heard of anyone changing over to the Yamaha snowmobile engine on their RAFs...The props have to usually be shorter to fit under the rotorblades, and still clear the keel. I would think the mast would have to be raised up quite a bit to allow a bigger prop diameter to handle the horses of the Yamaha. Wait...same size prop as used with the Subaru, but more blades would also work, like the New Mexico fella said he went to.
Alan: It was nice meeting you @ the last chapter meeting over @ the NWAAC clubhouse on the east side of Scappoose airport. It's good to see more builders/fliers joining Chapter 73!