Sled engines

[Mayfield]

It appears that Yamaha sled engines have been installed in some gyros for about 13 years or so.
I'm curious about the pros and cons of these installations.
I've read the threads Kevin has provided. I've also read about a few installations that seem to work well.

What appears to be the primary reason they have not become common in the aviation community?
Jim

 

[Kevin_Richey]

Jim: I was very happy w/ the Yamaha snowmobile engine I had on my Sport Copter single place. It was like cruising around on a car engine's power, putting around in the sky.

I loved that it ran on regular automotive fuel. No longer did I have to utilize supreme gasoline as well as 2-stroke oil to fly with, like the Rotax 503 it replaced.

I figured the extra weight of some 40# over the weight of a Rotax 582 would be easily carried by the engine mount system of the SC, w/out adding extra supports. I did not consult w/ SC about changing to the extra engine weight. SC later offered advice that I should replace the aluminum mast w/ one of their new steel ones, in order to handle the extra weight, or, add a strap system from the keel up along the mast in case the mast failed.

The extra mast bracket attached above the engine supplied by Todd Rieck's conversion package gave me piece of mind about the engine being supported/pushing the mast in two locations, instead of only through the horizontal engine support tube.

I was cognizant of the extra torque applied to the gyro air frame than what the Rotax 503 had that it replaced. I did not reef in full throttle when needed. Instead I gradually increased throttle when needed, just like I do when driving an automobile. I never encountered a case in flight where there was any issue when backing off on power by chopping the throttle.

I sold that gyro when a fellow PRA chapter member offered to buy it from me. I used the proceeds to pay off the land contract I had on property in AZ. A couple of years later, a neighbor there offered to buy that five acres for almost double what we had paid for it. I took that amount to buy another couple of parcels nearby.

That fellow PRA member gave up on his dream of flying gyros for two reasons:
1. He couldn't find local gyro training in the area. He runs his own trucking business that doesn't allow him time away to travel for out-of-state gyroplane training.
2. His health conditions helped him decide not to fly after all.

He has offered to sell it back to me. I'm very tempted, but would have to go into debt to do so...

I did have what I consider a minor issue w/ that engine, which applies to all engines. It was apparently too rich for high altitude flying. It worked fine w/ a cheap, homemade muffler. No issues for flying @ the Alvord Desert in far SE Oregon (4K ASL'), El Mirage (3K' ASL), ROTR (4K' ASL) in Brigham City, UT, or northern central AZ (4.5K' ASL).

I admit to being a flyer more than a mechanic, so I never addressed the rich condition. Probably changing the main jets may have solved that issue. The Yamaha sled engine w/ the carbs were supposed to be altitude-compensating. My guess is w/ the FI engines, those problems went away, w/ better fuel economy & power available.

When I changed to the original, heavy Yamaha muffler, I got some 500 more rpms @ full throttle in the low levels ASL. But, when I got to the high elevations, it stumbled & choked @ full throttle w/ that muffler. I also had installed a new intake pipe, made by the guys who pioneered the Millenium helicopter changes to the Mini-500. I left my old intake @ home on that trip, after testing it out @ low elevation.

I took off the muffler, running just the stock exhaust pipe. It seems to be back to normal running, but I didn't test it @ higher elevations b/4 selling the machine. Several people advised me that running the exhaust pipe w/out a muffler wouldn't damaged the exhaust valves of current manufactured engines vs. ones of decades prior, when valves weren't made w/ superior materials like now.

I did hear of another same engine set up (YG3, as Greg Mills likes to call them) in UT. It ran fine for many hrs., until one flight it dropped down 3K engine rpms. The pilot was flying it around the Moab, UT area when this happened. He stopped flying it there after that. He went home & rebuilt the three carbs, thinking that might solve the problem. It didn't, as the next test flight had it happen another 3K rpms!

He asked to borrow my electronics from a spare engine I had, to diagnose if it might be the culprit. He had those electronics for a year before sending them back to me. I don't know if he even tried to solve the issue. He gave up flying his Butterfly gyro, claiming he was tired of pouring too much $$ into it. He had three engine seizures from those three (Rotax 618 & 670) b/4 changing to the Yamaha.

I had heard of another Yamaha engine failure, in LA. It was from a sled that had been in water, they found out later when tearing it down. Two of the three cylinders & pistons had water level marks on them. The engine case had signs of being submerged. Apparently the engine wasn't examined very well b/4 being flown on the gyro. Fortunately the seizure happened over the airport runway, so the pilot just set it down after executing a 180 degree maneuver.

I think the Yamaha snowmobile/sled engines offer a lot as a successful power plant for aviation. Several airplane owners have changed over to the Yamaha high-powered sled engines, winning various STOL competitions around the country. Search for Steve Henry as the pilot/owner of the most competitions won. There is a FB page for Yamaha engines for flight. A fellow in Phoenix has made gearbox reduction drives for the 4 cyl. engines for years now, starting w/ his own trike.

Having some 200 HP available w/ lighter weight than the traditional Lycoming/Continental packages as well as less expensive acquisition & overhaul prices makes the Yamaha engines appear to be successful.

Some flyers like the idea of using the Yamaha 2 cyl. sled engine as a replacement for the Rotax 582. 80 hp vs. 64 HP. Slightly heavier by some 20#. Regular gasoline (less cost than premium) & no expensive 2-stroke oil to mix.

Some people, such as Vance, state that they haven't seen a single successful Yamaha engine replacement. Greg Mills claims lots of successful Yamaha engine conversions flying many thousands of hrs. w/out any problems.

 

[Mayfield]

Thanks Kevin. I personally have not examined any Yamaha powered aircraft. It sounds interesting.

 

[Vance]

Some people, such as Vance, state that they haven't seen a single successful Yamaha engine replacement. Greg Mills claims lots of successful Yamaha engine conversions flying many thousands of hrs. w/out any problems.

I have not written that I have not seen a single successful Yamaha engine replacement.
I have written for example; of the four Yamaha powered gyroplanes at an event I went to in Texas only one was flying.
One person had destroyed two Yamaha engines on his Tango.
A friend of mine in California had replaced one Yamaha engine on his Tango after a catastrophic failure.
I have not seen a Yamaha conversion where there were no problems.
I do not expect any conversion for aviation use to be trouble free despite what some people claim.
It appears there is a water pump impeller problem on some of the Yamahas.
Some people have had trouble with the propeller speed reduction unit.
Many Yamaha conversions have experienced exhaust challenges.
The three cylinder engines are very loud without a very large muffler.
I like how light the Yamaha engines are and if you are willing to operate at high rpm the engines make a lot of power for the weight.
High rpm can be hard on some PRSUs.

 

[Kevin_Richey]

I stand corrected!
Vance said: "I have not seen a Yamaha conversion where there were no problems."

 

[BEN S]

I remember visiting with Todd and seeing his rig he was putting the finishing touches on. I was surprised by how large the engine was, but it was also tilted in such a way as to appear larger then a lycoming.
He wasputting on a psru at the time.
I remember your rig Kev, and how you went from a 503 to an L-1011
I would LOVE to have an 80hp engi e on my Spirtcopter when the Rotax is doneski, but at the rate I am flying I will be 227 years old before its tbo.
Yamaha annoumced they were entering the experimental engine market and then poof...nothing.
Imagine if you could just buy an 80hp drop on optimized for aviation usage!

 

[Kevin_Richey]

...I would LOVE to have an 80hp engi e on my Spirtcopter when the Rotax is doneski, but at the rate I am flying I will be 227 years old before its tbo...

 

[GyroRon]

You have to keep in mind.... No one is buying brand new sled engines to use for their conversions. Instead, people are buying older used sleds, often wrecked ones, for as cheap as possible, then pulling the engine and harness to convert. That could explain some of the issues people have had.

On the yamaha I had, my only issues once I had it jetted properly, was the clutch was wearing out very quickly. And the clutch was one of the only parts on my engine that was " Homemade ".... I think had I been able to use the stock RK400 clutch shoe assembly ( it was not the shoes themselves but the part the shoes ride in that was wearing quickly ) I might have been able to get longer life out of it. No biggie though, the clutch still would work, but you could hear the shoes would get loose and you would need to replace shoes and eventually the drive hub.

Mine was the 3 cylinder engine, with carbs.

The 4 cylinder engines are much easier to mount a gearbox to, with parts made by Teal. I think what Todd ( Racer ) did was groundbreaking, but Teal with his CAD design and CNC machining perfected the process. If I were to do another engine today, it would be the four cylinder with Teals reduction adapter. I believe then I would have a engine I could say is as reliable as any thing else out there short of a Rotax 9 series or Lycoming/ cont engine.

Anyone thinking a engine NOT designed for aviation use is going to be more reliable than one that was designed for aviation is a fool.

But compared to any two stroke engine, or " professional " auto engine conversion ( think Viking or aero momentum for example ), a Yamaha sled engine properly converted should be as reliable or more reliable than any other non aviation engine.

You have to understand that a big Lycoming is not only very expensive new, they are also big and heavy. Not suitable for many smaller lighter gyros.

And as good as the Rotax four stroke engines are, they are also extremely expensive not only to purchase but also to service. And guess what.... They aren't bulletproof, there are plenty of documented engine failures with Rotax 9 Series engines... Plenty of documented failures in Lycomings too for that matter.

Nice thing about a gyro is so as long as you didn't fly over a area that is completely void of landing options, landing a gyro with a engine out should be no big deal. You can set it down in a very small area, smaller than almost any other aircraft would need.

You would be a fool in my opinion, regardless if you got a 30 grand Rotax, or a 12 grand yamaha powering your machine, to fly over open water out of glide distance of land.... or heavily forested area with no clearings.... or super congested areas ( such as flying over new york city for example ).

Of course we all eventually form some level of trust in our powerplant and we all will fly at least to some degree over stuff we can't land on... So I understand how some form enough trust to fly the hudson for example. I would probably feel better flying the hudson with a lycoming or Rotax 912S powering my machine verses some junkyard subaru conversion or even a Yamaha ... But I wouldn't make a habit of flying over stuff like that regardless.

Even when using Rotax engines, smart folks understood that those engines can still fail. That is why the one application where flying over hostile terrain, where a damage free engine out landing was impossible was the intended mission.... It was decided that the only option was to have two engines. Thats how the Drifter ultralight / LSA was transformed into the AirCam.

 

[BEN S]

"You would be a fool in my opinion, regardless if you got a 30 grand Rotax, or a 12 grand yamaha powering your machine, to fly over open water out of glide distance of land.... or heavily forested area with no clearings.... or super congested areas ( such as flying over new york city for example )"
Well Shit....anyone want to buy a Sportcopter Vortex?

 

[Tyger]

And as good as the Rotax four stroke engines are, they are also extremely expensive not only to purchase but also to service.

You remark on a "30 grand Rotax" vs "a 12 grand Yamaha", but the Rotax I have (912ULS) is only 20 grand, brand new, with a 2000h TBO.
I have not found it extremely expensive to run or to service. But maybe that depends on what one considers "extremely expensive", and who is doing the servicing...

 

[Tyger]

"You would be a fool in my opinion, regardless if you got a 30 grand Rotax, or a 12 grand yamaha powering your machine, to fly over open water out of glide distance of land.... or heavily forested area with no clearings.... or super congested areas ( such as flying over new york city for example )"
Well Shit....anyone want to buy a Sportcopter Vortex?

Here today, Guam tomorrow...

 

[BEN S]

I only maintain my gyro and flight status in case the island starts to tip......
My wife will get a crash course in paramotoring!

 

[GyroRon]

You remark on a "30 grand Rotax" vs "a 12 grand Yamaha", but the Rotax I have (912ULS) is only 20 grand, brand new, with a 2000h TBO.
I have not found it extremely expensive to run or to service. But maybe that depends on what one considers "extremely expensive", and who is doing the servicing...

Its been a while since I have priced out the 100HP 912S. I remember it being about 20 grand for the base engine several years ago, before the Covid inflation that seems to have jacked everything up significantly in price. Base price did not include a exhaust, radiator, oil cooler, hoses, etc.... I am not even sure it included the oil tank or voltage regulator or any of the other things needed to run the engine. You could easily spend another 2-3 grand on the stuff needed to make the engine a complete package on top of the 20 grand the engine itself costs.

The 115HP 914 was easily a 30 grand engine even 10 years ago.

And now there are several new models with fuel injection, and I have no idea the costs on those although I am sure its over 20 grand.

20-30 grand on a engine is ALOT, for a lot of folks. So there are going to be people who want cheaper alternatives.

To put in perspective though, say you like boats... you can spend WAY more than 20 grand for a outboard engine! Even a very common 150hp outboard can cost you around 15 grand. But a pair of 250 hp outboards will make spending 20-25 grand for a rotax 912 seem cheap.

As for servicing, or repairs.... The parts cost is very high. In comparison to what similar parts would cost for the yamaha sled engine. And labor wise, you need a Rotax certified mechanic to do certain repairs, where as the yamaha could be rebuilt or repaired by any decent motorcycle mechanic.

I will say that the Rotax engines, once set up properly, do not seem to need much other than oil changes for the most part. But follow the book for service requirements and there is some stuff that your supposed to do that can be expensive over time.



The flip side to this is you probably won't have a good Yamaha sled engine set up for less than 10-12 grand... by the time you acquire a good sled, and buy a redrive and adapter, clutch, have a good exhaust made, buy all the hoses and radiator, have the wiring harness remade, etc.... You could end up saving 10 grand or more ( I say "more" because the yamaha makes more power than the 914, so its more comparable to the 30 grand rotax 914 than the 20 grand 912s ) But for some folks, it might be worth the extra money to go with a engine that is a known factor, that is typically install and go fly and not have issues, a engine that is known to be reasonably reliable.

My airplane I am flying these days is a Vans RV4. I have followed the Vans aircraft line for decades and although there are the occasional build where someone has decided to try a subaru or mazda engine in one, or even a Yamaha ( someone is putting a Yamaha in a RV7 right now ) the mass majority of builders just stick with the tried and true Lycoming engines the plane was intended to run.

 

[N962GT]

I have not seen a Yamaha conversion where there were no problems.

Vance saw my Mohawk Aero Yamaha Genesis 4-cylinder (YG4) Air Command Tandem fly at Bensen Days 2013, and again at Mentone 2015.
This establishes he has "seen" it, personally.

Next, NOTHING has EVER gone wrong with this YG4 Air Command conversion. In fact it was perfect right out of the gate, the only adjustment ever made was stick movement after first flight.

Oh, I'll grant you I had a wire break and go to ground, one that broke while the engine was being removed from the sled and the rubber repair failed after 20 hours in the air, but it happened 6 miles out and the YG4 never skipped a beat all the way back, landed just fine as if nothing was off. The only way I knew something was amiss was the tach went blank.

OK, so last year I cracked a header. That can happen to any engine, but let's consider this cracked header started out life in 2003, 18 years prior.

Vance, you are so busted.

 

[N962GT]

It appears that Yamaha sled engines have been installed in some gyros for about 13 years or so.
I'm curious about the pros and cons of these installations.
I've read the threads Kevin has provided. I've also read about a few installations that seem to work well.

What appears to be the primary reason they have not become common in the aviation community?
Jim

Warning, Will Robinson, Warning! Vance Breeze alert! who in fact NEVER built/rebuilt a gyrocopter, and NEVER made any major changes/improvements to any powerplant or airframe, let alone owned or extensively operated any Yamaha of any type or configuration.
Why am I not surprised that he offers some stuffy, self-important opinion, instead of doing the right thing and pointing the guy to someone who actually knows what they are talking about for a change? But, then, he wouldn't be Vance Breese, would he? And we would all have to check our pulse to see if we're still alive and not ascended to that big gyrocopter airport in the sky.

In fact Vance is, without a doubt, the person here with the LEAST amount of knowledge on the subject by a LO-O-O-O-NG shot. Now take Ron Awad, or the other great and humble folks on here who actually have OWNED, let alone built, something resembling what you are interested in. Me? NOT humble. In fact I'm a loud mouthed autistic 'tard who never knows when to STF...trouble is I know something too, and when I know something I get REALLY obnoxious. Sorry, been that way for 68 years, tain't gonna change now... I warn you I have a bad habit of telling everyone what I've done, the accomplishments and successes. It's not bragging, really. I know that's hard to swallow, but every time I activate a new post I dont' know if the readers know who I am and why I say the things I do so I constantly go into reference history mode...part of the autistic thing. My teenaged kid makes fun of it constantly, I dont' take offense. It just is what it is, so far as I am concerned. anyways....

Visit www.MohawkAero.com, and send in the contact form at the bottom of the landing page and include as much detail info as you can Or email [email protected], this address has been in use since 2013. Please refrain from calling, I have a bad habit of talking too much and then I get no real work done.

Mohawk Aero Corps (MAC) has ZERO forced landings due to power plant failures of any sort flying Yamaha Genesis 4-cylinder (YG4); while coupled to the most numerous combinations of PSRU ever, including Arrow, Rotax C, Rotax E, SPG4, AK7, Simonini, and the hugely successful MAC prototype Hy-Vo chain Silent Drive. I have no record of any Skytrax YG4 forced landing failures but you'd have to confirm with Teal.

I warn against Rotax C with this engine because the front pinion bearing is not rated for it. In fact to date we have recorded a dozen Rotax C bearing failures on Skytrax RX1 adapters since I started telling the guys on here in 2014 this was going to happen. I also have customer airboats that I built Rotax C conversion kits for that didn't last to 800 hrs either, which proves it's the gearbox, not anyone's adapters.

My guys run their boats 8x7 during shrimping season, reporting 3 Rotax C failures, 2 this season.

You can buy a new YG3 from Arctic Cat for $5000. I've never built nor sold a YG3 conversion or parts, never owned a flying YG3. I bought a YG3 Nytro EFI with rolling gyro airframe, rotor and prop earlier this year to test my recommended fix for the chronic cooling system problems they have...

For now my advice is to go with a YG4, and if you are building a gyro, or any type pusher, stay away from Skytrax. If you are building a tractor FW with an Apex then I highly recommend going with Skytrax, and I send all those customers coming to me for advice over to Teal. Why? CoM, man. The prop is way high on a Skytrax PSRU which makes it great for tractor FW, but really not good for any pusher FW or gyro. I also recommend staying away from the Skytrax RX1 adapter since it uses Rotax gearboxes only. Either the C box, which is going to fail - not "if", but "when" as we know for certain by now - or the "E" box which is simply overpriced, and better equipment is available through MAC at a lower prices. If you really want to use "E" there is nothing wrong with it except price, and I have built plenty of "E" conversions for customers. If you come across a Skytrax RX1 adapter, I will machine the starter plug and gearbox housing necessary to fit Skytrax (and MAC) RX1 adapters.

Another reason not to use Skytrax on a gyro is that no one makes YG4 wire looms for gyro except MAC. If you can talk one of them into it, it will cost upwards of $3500 for pretty much the very thing you actually need which I still provide for only $500. Photos available of my most recent work.

YG4 conversions are bullet proof. Period, end of discussion, whatever else anyone here might have to say to argue the point is just going to put such ignorant, arrogant prejudice on public display....again.

YG4's are now, 10 Years After, PROVEN to be MORE reliable than Rotax, with much more HP at the same weight as 912 100HP; LESS weight than any turbo 912/14/15 by at least 20#. YG4 is normally aspirated, allowing you to run WOT as long as you want w/o blowing the engine up like all Rotax turbos at LESS power than YG4. Price? Don't make me laugh, I do complete conversions for ~$8000, send for my current itemized price list, engines are still available from $2500 and up. RPM? The engine internals are designed for 16,000 RPMs redline in R1 motorcycles. Same rods, pistons, valves, internal everything, just different cams for a different power band on the sled using a CVT tranny, and a different crank with a wonderful gift called a countershaft with a harmonic damper - the coup de gras and a flyer's dream for decoupling harmonics between crank and prop. No such thing as a "Do Not Run At xxxx RPMS" to worry about due to dangerous harmonic wave construction coupling the crank and prop, PSRU or no PSRU.

We run them at 1/2 the R1 bike RPMs, cruising at 7000 - 8000 RPMs. I have a YG4 customer approaching 900 hours, and a fleet with 15,000 hrs., all with ZERO forced landings due to power plant failures.

Well this has been fun, back to work!

 

[HobbyCAD]

Why not many running the YG3 FI version? Seems slightly beefier than the YG3 carby version? No altitude issues, and the EFI will compensate.

Mine's running well on the ground, not noisy at all, yet have to take flight with it.

Cheers, Francois.

 

[Sv.grainne]

Wow!

 

[Vance]

Warning, Will Robinson, Warning! Vance Breeze alert! who in fact NEVER built/rebuilt a gyrocopter, and NEVER made any major changes/improvements to any powerplant or airframe, let alone owned or extensively operated any Yamaha of any type or configuration.
Why am I not surprised that he offers some stuffy, self-important opinion, instead of doing the right thing and pointing the guy to someone who actually knows what they are talking about for a change? But, then, he wouldn't be Vance Breese, would he? And we would all have to check our pulse to see if we're still alive and not ascended to that big gyrocopter airport in the sky.

In fact Vance is, without a doubt, the person here with the LEAST amount of knowledge on the subject by a LO-O-O-O-NG shot. Now take Ron Awad, or the other great and humble folks on here who actually have OWNED, let alone built, something resembling what you are interested in. Me? NOT humble. In fact I'm a loud mouthed autistic 'tard who never knows when to STF...trouble is I know something too, and when I know something I get REALLY obnoxious. Sorry, been that way for 68 years, tain't gonna change now... I warn you I have a bad habit of telling everyone what I've done, the accomplishments and successes. It's not bragging, really. I know that's hard to swallow, but every time I activate a new post I dont' know if the readers know who I am and why I say the things I do so I constantly go into reference history mode...part of the autistic thing. My teenaged kid makes fun of it constantly, I dont' take offense. It just is what it is, so far as I am concerned. anyways....

Visit www.MohawkAero.com, and send in the contact form at the bottom of the landing page and include as much detail info as you can Or email [email protected], this address has been in use since 2013. Please refrain from calling, I have a bad habit of talking too much and then I get no real work done.

Mohawk Aero Corps (MAC) has ZERO forced landings due to power plant failures of any sort flying Yamaha Genesis 4-cylinder (YG4); while coupled to the most numerous combinations of PSRU ever, including Arrow, Rotax C, Rotax E, SPG4, AK7, Simonini, and the hugely successful MAC prototype Hy-Vo chain Silent Drive. I have no record of any Skytrax YG4 forced landing failures but you'd have to confirm with Teal.

I warn against Rotax C with this engine because the front pinion bearing is not rated for it. In fact to date we have recorded a dozen Rotax C bearing failures on Skytrax RX1 adapters since I started telling the guys on here in 2014 this was going to happen. I also have customer airboats that I built Rotax C conversion kits for that didn't last to 800 hrs either, which proves it's the gearbox, not anyone's adapters.

My guys run their boats 8x7 during shrimping season, reporting 3 Rotax C failures, 2 this season.

You can buy a new YG3 from Arctic Cat for $5000. I've never built nor sold a YG3 conversion or parts, never owned a flying YG3. I bought a YG3 Nytro EFI with rolling gyro airframe, rotor and prop earlier this year to test my recommended fix for the chronic cooling system problems they have...

For now my advice is to go with a YG4, and if you are building a gyro, or any type pusher, stay away from Skytrax. If you are building a tractor FW with an Apex then I highly recommend going with Skytrax, and I send all those customers coming to me for advice over to Teal. Why? CoM, man. The prop is way high on a Skytrax PSRU which makes it great for tractor FW, but really not good for any pusher FW or gyro. I also recommend staying away from the Skytrax RX1 adapter since it uses Rotax gearboxes only. Either the C box, which is going to fail - not "if", but "when" as we know for certain by now - or the "E" box which is simply overpriced, and better equipment is available through MAC at a lower prices. If you really want to use "E" there is nothing wrong with it except price, and I have built plenty of "E" conversions for customers. If you come across a Skytrax RX1 adapter, I will machine the starter plug and gearbox housing necessary to fit Skytrax (and MAC) RX1 adapters.

Another reason not to use Skytrax on a gyro is that no one makes YG4 wire looms for gyro except MAC. If you can talk one of them into it, it will cost upwards of $3500 for pretty much the very thing you actually need which I still provide for only $500. Photos available of my most recent work.

YG4 conversions are bullet proof. Period, end of discussion, whatever else anyone here might have to say to argue the point is just going to put such ignorant, arrogant prejudice on public display....again.

YG4's are now, 10 Years After, PROVEN to be MORE reliable than Rotax, with much more HP at the same weight as 912 100HP; LESS weight than any turbo 912/14/15 by at least 20#. YG4 is normally aspirated, allowing you to run WOT as long as you want w/o blowing the engine up like all Rotax turbos at LESS power than YG4. Price? Don't make me laugh, I do complete conversions for ~$8000, send for my current itemized price list, engines are still available from $2500 and up. RPM? The engine internals are designed for 16,000 RPMs redline in R1 motorcycles. Same rods, pistons, valves, internal everything, just different cams for a different power band on the sled using a CVT tranny, and a different crank with a wonderful gift called a countershaft with a harmonic damper - the coup de gras and a flyer's dream for decoupling harmonics between crank and prop. No such thing as a "Do Not Run At xxxx RPMS" to worry about due to dangerous harmonic wave construction coupling the crank and prop, PSRU or no PSRU.

We run them at 1/2 the R1 bike RPMs, cruising at 7000 - 8000 RPMs. I have a YG4 customer approaching 900 hours, and a fleet with 15,000 hrs., all with ZERO forced landings due to power plant failures.

Well this has been fun, back to work!

The Predator has over 2,200 hours on her and my friends and I installed a Lycoming IO-320 B1A in place of her O290 G with around 400 hours on her.

It was not a simple project and I would not recommend it for someone without experience despite the IO-320 B1A being an engine designed for aircraft. The O-290 G was not designed for aviation although it had been modified for aviation use.

Beyond normal maintenance the installation has been trouble free for 1,800 hours with much of that as a trainer.

I feel safe in saying that I have considerable background with engines, dynamometers, design and manufacture.

I also have experience with people who simply make things up about horsepower, testing and reliability.

I have found they often resort to personal attacks.

I don’t know anyone who has had a trouble free Yamaha sled engine in a gyroplane experience although I suspect there are some.

Ron certainly had some challenges.

A person converting an engine for gyroplane use that was not designed for a gyroplane is bound to run into some challenges.

Anyone who thinks converting a Yamaha to power their gyroplane is like buying a Chevrolet crate engine for their automobile will be disappointed.

There have been many failures of the supposed to be super reliable Yamaha three cylinder engine.

An engine failure is an unpleasant way to find that the water pump is not very good.

The four cylinder engine appears to me to be more robust for aviation use although it is still battery dependent and not well tested on gyroplanes.

Perhaps some day we will know everything about using a Yamaha engine on a gyroplane. It is clear to me there is still a lot to learn.

My hope is that N962GT will grow up so he can continue to post here.

 

[Georgi]

Here we go.......the same smell

 

[N962GT]

Why not many running the YG3 FI version? Seems slightly beefier than the YG3 carby version? No altitude issues, and the EFI will compensate.

Mine's running well on the ground, not noisy at all, yet have to take flight with it.

Cheers, Francois.

There are some 47 flying Tangos built and sold 2016-2019, all running the Nytro YG3 EFI, 1049cc 135HP coupled to a Gearbox350Type B Tango liked to call its SPG, with aligning groove cut into the rear housing face and mounted on a Tango disk adapter; and coupled to the PTO shaft via a Tango centrifugal clutch. There are some that seem to have the well-known water pump cavitation > impellor failure problems like Tom's in Texas, while others have put plenty of hours on them with no water pump failures like Jon Carleton, and most recently Scott M. who installed a brand new Arctic Cat YG3 135HP and has been enjoying a couple hundred trouble-free hours with it since, this year. Jon did things a bit differently, putting a secondary radiator above the engine to help bleed air off which seems to be working, but I still recommend putting the burp tank upstream of the "T" coupling and thermostat, to burp out any air to prevent it from recirculating prior to the engine warming up and the thermostat opening, just to be on the safe side.

The first Yamaha conversions done by Todd Reick between 2007-2012, and then his following kits built up to about 2015 before he retired due to medical issues, were all 120 HP 973cc carbbed Vector/Venture/Viper type, using a rather strange box adapter that surrounded the entire engine and was part of an engine mounting modular frame, quite complex, expensive and bit heavy. These all used Rotax C gearboxes and RK400 centrifugal clutches. To the best of my knowledge, Todd steered clear of the 135HP YG3 because he didn't think the C box would hold up to that much power over the long term.

Like Ernie Boyette with the first YG4, Todd took a stab and failed at converting a Phazer YG2 for a FW tractor application around 2014/15. They had many problems getting the 80 HP twin to spin up the prop, finally put a little turbo on it and got it to spin up at last, then there was an oiling failure that burned up the turbo and Todd and his customer threw in the towel. Nobody else was successful with the YG2 until 2019 when I was asked to give it a go and built one for my customer who put it on his Quicksilver float plane:

First successful Yamaha Phazer 2-cyl

It was a complete success, and since then many new builders have sprouted up doing there own thing with YG2's as well as several more kits sold out of the MAC shops.