Teal

As a update to Steve Henry's highlander RX1. He is replacing the header for one that has longer primary pipes so he has better low end power and better throttle response. He is having trouble making spot landings for competition purposes. I have been using a different header here lately and it really changes the low end torque. Wide open power is stiil about the same.

27 inches from the stator cover to the prop flange

Over 30 hours logged so far.

Steve Henrys Highlander with the 140 HP RX1 engine and Skytrax adapter

this is my 3rd generation skytrax

Steve Henry has gotten a few hours on his machine. He is pretty pleased with the performance so far here. So far he reports its performing comparative to his 914 that he had larger bore cylinders.  here is a couple pictures.

Here is clever way to mount the airbox someone did on a trike. 

No, I was just saying there are a lot of options for 70 inch props out that will work on the RX-1. I would suggest if using a 2 blade run the 2.62:1 ratio and a 3 blade use the 3:1 ratio. Steve Henry is using the 3.47:1 with his 80 inch prop. But remembee for those out there calculating tip speeds and effiecencies. The RX-1 has a 1.19:1 built into it. So for example the 3.47:1 is really 4.13:1 from prop to engine.

There are a lot of propeller options out there in the 70 inch range.

Im sorry I don't understand your questions, what options as far as propellers or what gearbox ratio options?

Steve Henry made his first flight with his RX-1 powered Highlander. First impressions are really good. He reports a stronger feeling of acceleration on take off. No testing yet as far as takeoff distances and climb rates. He has only made one flight so far but as numbers goes here is the numbers in comparing static runs between his 912s with 88mm pistons (aprx. 115 HP). The 912 used a 80 inch diam.  X 42 inch pitch propeller, he was able to turn it 2180 RPM on the prop staic. The RX-1 engine is turning a 80 inch diam. X 46 Inch !!!! and it is turning 2180 RPM static. He believes his 912s with larger bores was closer to 120 HP and the RX-1 is definitely doing more work. More to come on climb rates and take off distances. As far as HP for the Kitfox it's definitely more than it needs but I don't think it will necessarily be over powered. That's kind of like a girl to pretty.....

What is your source of information on the number of yamaha sleds sleds made? 

Rotax c gearbox should be about 11 lbs and my adapter is less than 2lbs

The 4 cyl. Is a bit longer but it is practically the same weight. I'm not a resident expert on the 3 cyl. But I'm told it has a heavier crank shaft aND it runs a balance shaft along beside the crank. The 4 cyl. Is really smooth without a balance shaft. The rx1 or 4 cyl. Weighs 128 lbs. With no carbs or exhaust. Steve Henry's engine in the above video was only firing 3 cyl. I spoke with him and he said #2 cylinder carb. Had a plugged idle jet. So it will sound much smoother when he is done. And I don't know of a easy way to add a second ignition but I do agree that these ignition are super reliable. 

That engine is probably making that much hp at a lower rpm than the RX1. The clutch as with any centrifugal clutch grips harder the faster you turn it.

No, I do not plan to.

Are you sure your not confusing the apex engine with rx1. The only limp mode I found was with throtle overide and that is easily bypassed. The gearbox is slanted to bring the center of the prop. To the center of mass and engine mounts. It's 9 inches from the center of hub top most of engine. If the gearbox was straight up it would only gain about 3/4 inch. My kitfox cowl is round and looks like it will fit just fine.

Oh and as far as flying a trike with the 912uls and the RX1, You can feel the acceleration and take off performance increase but trike's can not use that much power unless you have a really fast wing. So you end up not holding the throttle very long because you end up heading straight up in the air. Its a lot of fun but I look forward to seeing how fast it will launch a kitfox off the ground.

To answer some questions:

1) The adapter kit is $1500 and includes the adapter and hardware to mount a C gearbox.

2)The cost engines just depends. I have found that it is best to find low mileage good shape snowmobiles and buy them complete. They sell for $3000-$4000. I personally have bought some for $1800.

3) So another question that hasn't appeared here but I would like to hit on is complete cost for a FWF package one will be into one of these engines. Now I'm not offering packages since I do not have a business nor the time to offer this kind of service I am just offering my experience with the cost so someone can make a better educated decision on whether this engine is right for them.  $1500 for adapter kit, $3500 for snowmobile, $1600 for new Rotax C gearbox plus say $1000 for nice AN fittings, Bottles, radiator etc. So your at a conservative $7600 for a 140hp engine package. Now for a lot of people this will come cheaper for instance they already have a used gearbox or they find a sled locally for $1800.  For many it may make more sense to keep a look out for the used 912 for around that price. For me I love having a modern 4 stroke that has more HP and is cheaper to maintain and buy parts easier.

4) The 140HP is at 10,000 RPM. Now the engine has a built in reduction of 1.19:1 and I have been either using the 2.62:1 or the 3:1 on my trikes depending on what propeller I use. I plan on using a 3:1 on my kitfox spinning a 74" prince P tip. Another fellow building a Highlander is using a 3.47:1 spinning a 80" prop. For everyone's calculation purposes here is the ratios for the engine to prop with the available rotax gearbox ratios (1.19 engine ratio) :    2.62:1 = 3.12:1    3.0:1=3.57:1  3.47:1=4.13:1 and  4:1= 4.76:1

5) I have done lots of thrust measuring. I have pulled pretty regularly 530lbs. I have pulled 570 lbs with the prince P tip 74". and the 3.47 rotax gearbox. I do believe there is more to be had since it sounded like the prop was cavitating. in comparison my 912UL kitfox pulls 320lbs and my buddys STOL plane with a 160 hp 0-320 Lycoming pulls 590lbs all pulls on the same day.

The reason for using the RX-1 for me was that it has a output shafts drive cover that could be removed and directly replaced by my replacement adapter cover so it is a real clean conversion. It is the same weight as the 3 cyl. Or within a couple pounds because the 4 cyl. Has a lighter crank shaft and has no counter balance shaft. It runs really smooth. The 3 cyl does not have any good provisions for mounting a gearbox and after you add mounting plates and hardware it will definetly be heavier than the rx1. Plus the RX1 has 20 more hp.

Hello, everyone I am new to this forum. I would like to let everyone know about a really good engine option. I have been using the RX-1 engines now to power my last 3 aircraft which have been trikes. I am a machinist by trade so I made a adapter that will allow the use of a rotax C gearbox with this engine. I recently bought a Kitfox model 4 that is currently being powered by a 912. I will be removing the engine and replacing it with the RX1. The engine weigh 128 lbs bare. they are 140 lbs with carbs gearbox and adapter. They up to 140 HP stock. 4 cylinder double overhead cams 5 valves per cylinder. They are super reliable with the snowmobile community. See my you tube video of me installing a adapter on a RX1 under  SKYTRAX YAMAHA. Steve Henry of wild west aircraft is currently installing one in his new highlander.