YAMAHA RX-1 (140 HP) install in Kitfox 5

109 posts in this topic

Posted (edited)

Ok guys.  This will be a big project for me and I'd like to lay out my plan of attack for ya'll to review as I go.   I will be thankful for everyone's help so please don't hold back if you have an idea or advice

I also hope that this build thread will provide good info for anyone interested in the Yamaha power option.

The goal on this one is a functional and safely done repower and install.  But this is NOT going to be a "show plane", so looks, beauty, and bling are low on the priority list.

So I got my bird crammed into my garage yesterday, pulled the prop of the subaru and am getting ready to dig in.   Here's my initial game plan:

1. Take lots of pics of the sooby and measure up location of prop flange to hopefully eliminate too much cowl rework in the end.

2. Pull the motor and take a look at the soob motor mount.  I was considering building off it if possible to simplify the fabrication process.  Any concerns with that?

3. Get things lined up, plan for airbox and exhaust, then tack together the new mount.  I am a novice welder and own only a cheapo wire feed welder.  I'd plan to emulate what others have already done and fishmouth the thing together and just tack it, then send it off to a pro to TIG it up and powdercoat.  (I'd be glad to hire out the entire mount fabrication but so far I'm the first guy I know of to put a Yamaha in a Kitfox, so it would presumably be hard for someone else to build me a mount without a KF5 firewall jig and a RX-1 motor laying around)  Any ideas / thoughts? 

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Edited by Yamma-Fox

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Posted (edited)

There are lots of posts in the 4-stroke section about the Yamma engine and I believe there may be photos of a mount - I don't know if it is for Avid or Kitfox.  Guess you have looked at them?  Maybe you should post your progress there?  Your NSI might be worth a little more if the mount was included.   Firewall jig is easy - clamp a piece of plywood and outline to your firewall and drill thru the mounting holes - weld up frame using that - Well, your firewall isn't flat, so you may have to build something to fit.  I went the opposite way - Had Pelican mount for my Soob and used it to add mounting bushings to firewall.  You could probably do the same with an Avid mount.  EDMO

Edited by EDMO

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Posted

There is probably a few different ways to build the motor mount ,we ended up bringing the tail up to level the plane and had a bench on wheels the exact high we needed to sit the RX1 on. When we had all the right angle and measurements from the firewall we installed the larger  main  mount to the motor and then tacked on each of the smaller pieces from the firewall to the main mount, There wasn't much room left from the back of the RX1 to the firewall on my avid but your kitfox may have more room depending on your cowling,

Good luck on it

 

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Posted

I don't have a gantry, but a fold-up 2000 lb hoist from Harbor Freight for about $179 made it easy to lift and move my Soob engine.  EDMO

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Posted (edited)

The easy part.

(Decided that the soob mount wasn't even close to what I'd need for the yammy)

Pic 2 shows tailwheel spring support.  With the motor off she'll be a wee bit tail heavy!

Pic 3 is my quick little (sorry ass) attempt for a prop flange locator jig. (Bolted to firewall)

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Edited by MN Kitfox 2

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Posted

Harbor Freight has two tables like this that jack up[ 500 to 1000 lbs about 3 feet, might that help mount that engine?

harbor freight.jpg

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Posted

What are you going to do for a wiring loom? I want to do the same conversion.

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Posted

What are you going to do for a wiring loom? I want to do the same conversion.

Mine is a carbureted (RX)-1 4cyl.  Teal Jenkins  (skytrax) sells the c box adapter and wire loom (which is very simple for that motor).   I believe he is working on an  adaptation for the EFI 4 cyl (Apex) as well, which requires a MUCH more complicated wire loom mod.

More info on the RX-1:

http://www.avidfoxflyers.com/index.php?/topic/4138-yamaha-rx1-engines/

 

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Posted

Harbor Freight has two tables like this that jack up[ 500 to 1000 lbs about 3 feet, might that help mount that engine?

harbor freight.jpg

I have one of the 500lb, and one of the 1000lb, they are the handiest things I ever bought.  If you need higher lift, Northern Tool has some that lift more than 2x these.  I haven't found a need for them yet, but I bought a forklift, so my lifting needs are pretty much taken care of.

Mark

 

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Posted

Roughly lined up. .. 

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Posted

I looked into the wire loom in detail.  

Teal has full (one page!) instructions and has made it super simple:

From Teals harness:  Hook up batt positive, ground engine to airframe (my airframe is common ground, I'll run a heavy wire to it from the starter mounting bolt on motor.  Hook up the ignition supply wire (I'm going to two switches for redundancy, one to hot batt, one to engine alternator/magneto).  Hook up starter solenoid wire to the start button in plane.

That's it!  Teal also has one wire ready for the tach and the rest are plug and play connectors to the small weatherproof ECU and VR boxes, and also to the spark plug caps (with built in ign coil on each)

I will add a fused switch to the electric carb heaters installed in the carbs on the yammy. This bird will fly all winter here in N Minnesota and the elect carb heat helps supplement the standard carb heat (heated by engine coolant) 

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Posted (edited)

the easiest way I came up with for the mount fab.  Make a jig that the mount bolts to, and that the prop flange bolts to all in one.  Unbolt the old engine and bolt the new engine to either the firewall of the prop flange and block the engine up.  Figure out how to fill in the blanks.  This will put the prop in the right spot on the cowling versus firewall for minimal if any cowling modifications. 

 

Look up the thread I did on the 912 mount.

 

Gives you an idea of what I am talking about.  I started with a 582 mount that gave me the firewall pattern.  Then I bolted the 582 and gear box to it so I could locate the exact prop location.  Pull the 582 and the mount and start filling in the blanks.  The first jig sucks.  The one you make to locate everything wont let you weld it out without having parts move around as you weld them so I ended up with 2 jigs.  One to tack everything in place and one to bolt all the hard points into to keep it immobile when welding.  After I welded it out I did a semi stress relief by heating up all the weld areas and heat effected zones and then wrapping it in insulation and let it slowly cool.  The result was a mount that did not wiggle when the bolts were pulled out of the jig.

 

:BC:

 

 

Edited by akflyer
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Posted

Hi I was wondering if I could bother you for a couple of measurements before I go look at this sled for sale.Prop flange to fire wall I have 24in. The problem I see is I have a lower step of 4in down 12in from the.top of my cowling. Thanks.

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Posted

Hi I was wondering if I could bother you for a couple of measurements before I go look at this sled for sale.Prop flange to fire wall I have 24in. The problem I see is I have a lower step of 4in down 12in from the.top of my cowling. Thanks.

No problem.  I'll send you a PM here when I get home and we can figure out how it'd fit.

Brett

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Posted (edited)

OK.  So a member here whom I highly respect brought up a challenge to a premise I had made when choosing the RX-1 motor for repower.  I am glad he did because it helped me come up with a plan to test my guesstimate.

My premise was that if an RX-1 lost a cylinder for some reason (bad coil, spark plug, burnt valve, flake of gunk plugging a main jet.... whatever) that it would still pump out about 70-80 hp running on the remaining 3 cylinders.  Note here that the RX-1 uses four fully independent "CDI/coils" integrated into each of the spark plug caps, so in a very loose sense it does offer some redundancy in the ignition system. 

Based on my experience with my 65 hp KF2 on lotus floats, I figure that 70-80 HP would be enough to eek out a meager climb (150fpm) in my heavier KF5 on lotus floats.

UPDATE / EDIT:  (Jan 2018)

Ok guys, finally got to that rx-1 test running with 1 (and 2) of the 4 cylinders down:

Yamaha RX-1 Performance Test on 3 cylinders:

So I put the theory to test out on the snow today by pulling a coil lead off a cylinder.

Results were better than I expected,  with an easily started motor, good idle, and an estimated 80 hp output.

Details of test: 2005 Yamaha RX-1, 30 deg F day (heat wave here in MN!) through 2" of loosely packed snow.  Top speed 78 mph with the #2 cyl coil unplugged.

That compared to a MUCH lighter 2012 Ski Doo 600 ACE (60 hp 4 stroke).  Top speed 64 mph.

For the 100 lb heavier RX1 to go 14 mph faster than the  ski doo in loose snow would probably take between 15 to 25 more HP.  (Note that a lighter 90 hp ski doo I ride occasionally would have gone about 80-85 mph in those conditions) 

So I am happy in those results.  The engine sounded and ran surprisingly well!  And 80 hp would be plenty to fully operate my kitfox 5 which was designed to use an 80hp rotax 912 as the normal powerplant.

Conclusion IMO is that dual ign is great.... but it only covers ignition redundancy.  I prefer that the yamaha (with it's extra power reserve) which could carry the day very well with ANY failure of power output from a single cylinder.

 

Running on 2 cylinders test:

Test results running on 2 cyls (#2 and #3 coils unplugged):

I'm really surprised by this one,  started right up, idled fine on the all cyl idle stop, ran 53 MPH down the trail!!

That's gotta be 50 HP!

I was guessing it would have done less, but that would keep me in a gentle drift down in the plane... giving 10 times the options and time for a emergency landing.

Really happy to see it perform like that!

Edited by Yamma-Fox
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Posted

Unless you adjust the RX1 clutching to make up for the 25% power loss this won't be much of an accurate test.

 

 

Ken.........

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Posted (edited)

Unless you adjust the RX1 clutching to make up for the 25% power loss this won't be much of an accurate test.

 

 

Ken.........

You're 100% right.

It'll be under revving and running lower in the power curve.  Capable of more HP if I reclutched for more rpm.

Hadn't thought of that.

But, thinking a bit farther, the same could be said for a fixed pitch prop on a plane where you suddenly dropped a cyl.  So in that sense it would be an accurate test, or at least accurately representative of the performance loss you might enconter.

Agree?

Edited by MN Kitfox 2
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Posted

yes I agree.  Your not going to stop and re-clutch / gear in the air.  Dont over think this one :lol:  Dropping a cylinder on the trail and dropping one in the air will be close to same as the clutching and the gearing / prop pitch will be pretty much the same load on the engine so I would say its going to give you a rough idea of what to expect.

 

:BC:

 

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Posted

he was referring to the snowmachine test. 

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Posted

I wonder how much lower the prop flange will be? If Teals adapter is 9in from center to top of motor.

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Posted (edited)

I wonder how much lower the prop flange will be? If Teals adapter is 9in from center to top of motor.

The engine is mounted at an angle toward the left, or normal pilot's seat, so you cant use that as an "up and down" measurement.  The rotax gearbox raises the height of the prop flange up from the center of the adapter.  Maybe someone can give you better measurements?  I don't think you can plan much until you get the engine and adapter.  EDMO

Edited by EDMO

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Posted (edited)

RX-1 ENGINE MEASUREMENTS  (with Skytrax adapter and c box attached)

For anyone considering this motor, here's some rough measurements:

Total length is right about 27.75" from back of motor to prop hub.

Total height about 18

From engine top to prop center is about 7.5"

Width about 13" (without exhaust or airbox)

Some tilt of the motor could be done (my install will be fairly vertical (see pics).  Tilting would make overall height slightly less (16 maybe) and width a little more (15ish).  Tilting would also bring prop center down and left slightly.

In my install, I am aiming for the prop hub to come out exactly where the subaru did.  This will require a hood cutout and "bubble" on the top to allow for the cylinder head to protrude about 2.5 inches (the subaru cowl was sloped down alot since that motor was a boxer: wide and not tall)

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Edited by MN Kitfox 2

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Posted (edited)

CARB CLEANING AND RX-1 SHOP MANUAL:

The most common question on the RX-1 snowmobile forum seems to be regarding rough running old sleds.  The canned advice I see a lot is "clean your carbs and post us in the morning".

I posted a reprint from an expert in the snowmo forum on how to clean these carburetors.  I also posted the RX-1  APEX and C Box service manuals here:

RVSimons did a beautiful job of cleaning up my carbs and supplying me with new orings for float bowl covers and main jet towers.  Thanks Vance!

I decided to go totally new in there and also bought the needle and seat kits which includes orings on the back side of the seat.  If they get crusty (see pic), pressurized fuel will leak around the seat and flood the carb.  My sled had that trouble and I just cleaned em up.  In the plane I want new.

 

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Edited by MN Kitfox 2

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Posted (edited)

And another quick tip from the sled heads.  Get sst socket head cap screws to replace the phillips heads holding float bowls on.  The damn phillips ones round out waaay too easy.

Size is M4x8

 

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Edited by MN Kitfox 2

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Posted

Keep the post coming, I an on the edge of my seat:BC:

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