Yamaha RX1 Engines

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Posted

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. 

IMG_3171_3 (1).jpg

20151031_101013.jpg

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Posted

Very cool, I was thinking of looking for a yamaha 3 cylinder genesis engine  and doing the conversion so would be interested in your adapter plate for the C drive.I don't know much about these engines so what is the reason for  you using the RX1 , I guess I thought the 3 cylinder would be lighter

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Posted

It will be interesting to see how this engine works out.  Would be nice to have a good alternative to Rotax$  Jim Chuk

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Posted (edited)

Teal,  Welcome to the forum.   Keep posting about the RX1 - I think you will have a lot of attention, and probably questions from members here.  Photos, flying reports, etc. are always great info.  Wishing the best to you.

What does this engine cost?  What will you charge for adapters?  What are the hp options?

EDMO

Edited by EDMO

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Posted

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.

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Posted (edited)

What kind of rpms does this engine run on?  Best redrive ratio?  Also, see above questions in my post. 

If I had a 2-stroke engine I would be seriously looking at this one.

 EDMO

Edited by EDMO

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Posted

Thanks for the explanation and appreciate the advice :BC:

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Posted

Thanks for the explanation and appreciate the advice :BC:

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Posted

What is the maximum RPM you run this engine at? What gear ratio for the gearbox?  Have you ever done a static thrust test on it?  You mentioned that a stock engine is up to 140 HP, what RPM is that at?  Thanks,  Jim Chuk

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Posted

Welcome and thanks for posting! I have been following Steves install fairly closely. How do the trikes do in comparison to a ULS?

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Posted

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.

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Posted

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.

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Posted

Thanks for bringing simple innovation to us.  

Me and you talked some 4-5 months ago.  I had just looked at your Kitfox in Tuscon the week before you picked it up. I'm sure that will jog your memory about our phone conversations  

After tooooo much thinking, I decided to rebuilt my existing 582 for simplicities sake and make a 670 out of it. If I had found a STOL plane for the same deal that I got on my Avid Aerobat I would have taken you up on your offer. I'm just a bit to fresh to be changing too many things around on my first airplane. And frankly, the 670 saves me a couple months of actual flying time vs rebuilding time.  I didnt want to burn myself out, which I often find myself doing, by taking on new projects  

 

You spent a ton of time on the phone with me, and as a small buisness owner, I know how hard that is to do with every looky loo.  Suffice it to say, that if any one of my fellow Avid owners is considering this engine upgrade, know that you're in good hands with regards to coustomer service and Teal. He's the real deal and is just like one of us. 

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Posted

Teal, I've considered this combo for my Zenith 701 project. My only concern is how to cowl this engine for my application.  Im pretty sure a stock Zenith cowl will not work for this engine with as much off set at it has. I'm just going by looks and wonder if you can tell me what the off set is from center of the prop hub to the top of the engine. Also can you tell me what and how you plan on addressing this issue on your Kitfox. I see the Highlander is using it and wonder how they will fit a cowl over it. So many good little small four stroke engine out there which have been slanted to fit under our cowls. I would appreciate any thought you might share. 

Thank you

Vance

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Posted

Teal, I've considered this combo for my Zenith 701 project. My only concern is how to cowl this engine for my application.  Im pretty sure a stock Zenith cowl will not work for this engine with as much off set at it has. I'm just going by looks and wonder if you can tell me what the off set is from center of the prop hub to the top of the engine. Also can you tell me what and how you plan on addressing this issue on your Kitfox. I see the Highlander is using it and wonder how they will fit a cowl over it. So many good little small four stroke engine out there which have been slanted to fit under our cowls. I would appreciate any thought you might share. 

Thank you

Vance

Certainly not wanting to cover up your questions,  but to add mine:  It looks like a standard Kitfox cowl will not fit - Why wasn't the adapter made so that the C-box would sit in a more upright position with the engine slanted?  Looks like it might work better that way, and raise prop height.  EDMO

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Posted

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. 

IMG_3171_3 (1).jpg

20151031_101013.jpg

Very clean installation.  Impressed with your workmanship and attention to detail.  What kind of trike is that?  I used to fly a Northwing a while back.

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Posted

Teal, I've considered this combo for my Zenith 701 project. My only concern is how to cowl this engine for my application.  Im pretty sure a stock Zenith cowl will not work for this engine with as much off set at it has. I'm just going by looks and wonder if you can tell me what the off set is from center of the prop hub to the top of the engine. Also can you tell me what and how you plan on addressing this issue on your Kitfox. I see the Highlander is using it and wonder how they will fit a cowl over it. So many good little small four stroke engine out there which have been slanted to fit under our cowls. I would appreciate any thought you might share. 

Thank you

Vance

Certainly not wanting to cover up your questions,  but to add mine:  It looks like a standard Kitfox cowl will not fit - Why wasn't the adapter made so that the C-box would sit in a more upright position with the engine slanted?  Looks like it might work better that way, and raise prop height.  EDMO

Maybe the adapter/C-box position works for trikes, but looks like it needs to be rotated upright for slanted engine in Kitfox.   EdMO

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Posted

I know when there on the snowmobiles if they start to over heat they instantly go into limp mode and and wont come off of an Idle till they cool down, How do you get around that, Just wondering,

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Posted

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.

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Posted

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.

I guess I was thinking the 3 cylinder Nitro engines, the 4 cylinders must be different then, thanks

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Posted

I know somebody that was flying with a Geo engine, thought he would get better climb if he put less pitch in prop,more RPM, long story short, geo,s have a reve limiter, went into limp home mode, tree top landing!!!

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Posted (edited)

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.

I was thinking more about putting the center of the prop on center with the plane - photo does not look like it would center in cowl.   Any increase in height is usually good too.    EDMO

Edited by EDMO

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Posted

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.

I was thinking more about putting the center of the prop on center with the plane - photo does not look like it would center in cowl.   Any increase in height is usually good too.    EDMO

The way it sounds ED with the slanted gearbox the prop will be in the center of the plane. If he was to straiten out the gearbox that would place the prop off center, Im kind of pumped to see how this engine works, I think it will be sweet, Of course not as sweet as my Jabiru ha.

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Posted

Here is the install of the adapter

 

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Posted

Just wondering Teal, are you using the rk400 clutch setup on the Kitfox project?

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