I REALLY dont want my build thread here to go off the rails, but although that Kawasaki motor is cool it has nothing over the Yamaha. Most importantly, this Kaw (along with so many other potentially great engine options) have no adapter-gearbox options available and also have not been proven out in the air for tens of thousands of hours like the Yamahas have. (There are now about 130-150 motors converted out there dating back over the past 10 years). As far as power capability, the 998 Yamahas will do 600+ HP at turbocharged drag racing boost levels, and about 280 HP reliably in boosted trail sleds (stock internals on Sidewinder motor, upgraded internals on others). And that is a big reason I chose this line of motors.... running in the 140-180 HP range is undeniably a huge derate from what they are capable of. http://www.powerbygns.com/Products.html
I just talked to a few people and came up with a couple degrees left and "zero" up/down. Nothing really scientific, might shim the mount a bit if I find I want something different. The skytrax apex (with it's 3 gear gearbox) turns a right hand prop as opposed to my left hand RX-1 so it could possibly benefit from a couple degrees right. The angle is to counter the P factor.
With that said, my dream motor in a "light" KF or Avid would be the 2cyl 4s Rotax 600ACE. It is small, reasonably light, high tech EFI, direct drive, and derated at 7300 rpm and 60 HP in the sled. That derate is to meet BAT noise and emissions standards that are required for snowmo use in Yellowstone Park and other places. I run one and it is my favorite snowmo motor ever... ultra quiet, ultra efficient (ACE stands for Advanced Combustion Efficiency), has a broad powerband with nice linear broad torque curve, and time proven reliable (out since 2010). People ride them until the sled falls apart around the flawlessly running motors (25,000+ miles) A little exhaust tuning and it can pump out the upper 60HP range at about 7800 rpm. That's where I run mine and it just purrs along at WOT for miles and miles and miles on end trying to keep up with higher HP sleds. I totally believe and would bet my butt (in a plane) that it would do 65 HP continuously for thousands of hours with no worries. Remember that the 500cc 2cyl 4s Yamaha Phazer reliably puts out 80 HP, and the 600ACE does well with turbo at 90-120 HP, so 65HP seems in contrast to be childs play. Teal has his hands full but I wish we could clone him and inspire the clone to make up a Integrated gearbox-adapter for the 600ACE!
My vote for a 2smoke would be the 600 etec. It really has the best track record and durability history. 120 HP but Id derate it to 100 max and 80 continuous. Biggest obstacle there is (as mentioned) the provisioning for an adapter and gearbox. IMO the 800 and even 850 etec just havent proven out well enough for use in the air. They have been "good" at best in sleds and I think Leni is right: among 800s the Arctic Cat motor has the best reputation.
Teal doesn't check in here as often as I do so I'll tell ya what he told me. Edge should hopefully be spinning up the turbo apex with this gearbox and a prop in Feb. They will push it hard (300 HP) and test the heck out of it. Assuming success I think Teal would be ready to release the gearbox shortly thereafter.... so my SWAG guess would be late winter - early spring. Below is the latest / updated gearbox design:
Yeah I had to get over that too! I am definitely not the smartest or most experienced guy here in this forum, but I might posssibly be the one who has researched, investigated, networked, and talked to the most people about this yamaha thing. And in all that research I have found the C / E gearboxes to be mega "overachievers". They definitely have an incredibly good track record on the Yamaha engines.
Reference post above, here is Thomas H's (Edge Performance) comments on the project: It’s Yamaha time. I’ll try and keep this post alive as we progress. Step one is to tear down the engine and inspect and measure the internals. Ultrasonic clean and bead blast all parts. Send off all steel parts for tumbling and cadmium/zinc plating. Next, install forged pistons and rods, new bearings, ARP studs and MLS head gasket. Make a mil-spec Raychem DR-25 motorsport harness and adapt the Apex engine to our ECU. Make a 4-into-1, S321 turbo manifold and fit a Garrett turbo. Thinking either GT2860R or GT3071R. We’ll see how bald we dare to be. Fit Teal’s Sky-Trax PSRU Run it like we stole it on the test bench and dyno. Gain data and numbers. * Maybe do a full head job with full radius cut valve seats, grind the valves, and possibly a 5-axis CNC porting job. Needed, NO! Would it be cool, YES !
Due an update here. Teal has made a few upgrades to the original design, to include a larger oil reservoir, an oil level sight guage, and helical gears. And bigger news (for anyone that has missed it) is that Edge Performance is working with Teal on a full zero timed Apex with beefed up internals and their fully automated aviation grade Turbo. Edge should be testing a prototype here within the next two months and Steve Henry is planning to be the launch customer. HP in testing will be in the 250-300 range. Production units are planned to go out in a detuned range of 180-230 or so. For reference, the Apex is run up to 600 HP in the snowmobile drag racing world. Basically, Edge is planning to do all the internal upgrades (as seen in the pic below and website link) that are used for the 600 HP race sleds, but send it out to only run it in the 180-230 range for aircraft use. http://www.powerbygns.com/Products.html Follow the Edge Performance build in the FB post here (click the "veiw on facebook" link)
My deal with Roman direct went well too. Long wait but good deal. Those props are a work of art. And I shoulda hired Fred to come over to do my engine swap with the same method used in the video above.