Info Yamaha triple for Ultralight engine

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Canuck Bob

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I have decided to convert a Yamaha sled triple to an ultralight engine. The prop reduction unit is reasonably easy but I know almost nothing about the various triple engines.

Can anyone point me to a site or thread that describes all the different triple engines?

I understand this forum is for the non power valve engine. I guess that the engines in the mountain and touring sleds are a little different. Also I read somewhere about a lighter crankcase, welded crank triple but not sure of which model. I've seen pictures of individual heads and triple bank heads?

Ultralight engines usually operate at full throttle for 2-3 minutes at takeoff and then about 65-75% power for up to 2 hours. Lots of cooling airflow available. Rotax 2 strokes operate at 6800 rpm max and 5800 for cruising but they are just not to my taste. I fly lo and slo so an altitude range of 3000 ft. is good. I believe the Yammy triple is much more reliable and smoother with a nice turn of power.

Any used sled model you might recommend for this conversion?
 
Yamaha triple Ultralight engine

I just posted a detailed thread in the Vmax, SXR forum but thought I would ask you guys and gals about the monster power available from these power valve engines for an ultralight engine.

I need an engine capable of full power for 2-3 minutes and cruise power of 65-75% for up to 2 hours. Lots of cooling air flow and kept in top tune would you trust one of these super tuned engines to be reliable? Please note an engine out is not as dangerous as many non pilots might suggest.

Can someone point me to a thread or site that details the differences with these different triples?
 
Canuck Bob said:
I just posted a detailed thread in the Vmax, SXR forum but thought I would ask you guys and gals about the monster power available from these power valve engines for an ultralight engine.

I need an engine capable of full power for 2-3 minutes and cruise power of 65-75% for up to 2 hours. Lots of cooling air flow and kept in top tune would you trust one of these super tuned engines to be reliable? Please note an engine out is not as dangerous as many non pilots might suggest.

Can someone point me to a thread or site that details the differences with these different triples?
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The power demand you require is do-able and I would think very reliable but I would think an air cooled version would be better suited for your needs. I'm not aware of any late model air cooled triple.

I don't think exhaust powervalves would be as big a benefit with an ultralight as they are with a snowmobile. I wouldn't think low-end throttle response is a critical.

Don't Ultralight engines need to be certified in some way? I'm not trying to talk you out of anything, I just don't think a liquid cooled triple with powervalves would be as efficient as anything air cooled and piped.

I keep pictureing in my mind a 4 cylinder free-air I saw in an old Arctic Cat. I remember 4 finned cylinder heads sticking out of the hood and think they called it Godzilla or some such thing. Good luck.
 
all the red head triples are the same, except for well, 600 cc and 700 cc, no difference if its from the Vmax, Venture, SXR or Mountain Max, motor wise there the same. The SRX has power valves and has stock triple pipes. The Viper motor is also power valved, but stock single pipe. Theres an 04 Viper motor on here for sale in Labrador for $1250 if you were looking for one.
 
Are you looking for an air cooled motor? I don't know how well some of these engines would hold up without some kind of liquid cooling method.
 
Thanks, air cooled is good but the Rotax history is full of piston seizures due to shock cooling. Hirth also makes aircraft 2 strokes and same thing, piston seizures. Water cooled is also a personal choice so I'm willing to live with the complexity. Also water cooled engines are more reliable (I think) for higher states of tune and the warm weather we fly in.

The Rotax UL engines vibrate too much, that's why I want the smoothness of the triple.

Ultralight engines can be anything one wants to convert. Factory aircraft engines are subject to very strict restrictions but homebuilt airplanes are left to the builders.

Prop reduction is usually in the 2.5 to 3 range so the multiplication of torque to the prop is huge.
 
Thanks to both of you.

Air cooled, 2 stroke engines are prone to shock cooling and piston seizures. I want to fly behind a warmed up water cooled engine.

Reliability, at least 80 horses, full throttle power, decent mid range torque, instant throttle response would be my wish list in performance. Pull start is fine but a starter is ok too.

Are the red head engines seperate heads or a single 3 cylinder head. I believe this is the engine everyone raves about for smoothness and reliability.

I've been reading posts about the Viper and SRX power valve engines and think the extra complexity is not needed for my application.

A single pipe is best but that is the area that will be challenging as far as fit and such is concerned.

I'm not ready to buy but will buy locally when the time comes as there are lots of Moutain Max's here in Calgary and Alberta.
 
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I've had a 582 engine out and these triples look perfect.

I'm thinking redhead engine and top notch performance mods to achieve 85+ hp.. Would you guys see any reason a triple couldn't pull 7500 rpm full throttle and say 6000 rpm cruise. The power curves I can find support these numbers. I could use a 3 to 1 prop reduction (PSRU) and generate tons of torque to a prop. It looks like 80 ft/lbs are doable and that means 240 ft/lbs to the prop! My plane would lose 75 lbs. gain 25% in hp and climb like a rocket.
 
I am thinking 7500 to 6000 rpm range but my buddy rides a 600 Yamaha triple and it is sweet when winding up.

I'm thinking a stock single pipe or maybe a can (? whatever that is) I've read about on here. Real good reed valves for broad powerband and quick response, any suggestions. And a Holtzman Ataac for fuel control.

Here's a newbie question, I'm assuming these engines have thermostats.

Any areas that should be upgraded for reliability? I've read of some early SRX crank problems, upgraded redhead cranks for 98, etc..? Any bad years for the CDI's or are there aftermarket CDI systems that are better?

Thanks to everyone
 
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correct me if im wrong but dont single piped redheads make the most power around 8200rpm?



EDIT:

the 97 SX had crank problems, there are no CDI problems that i know of, and i run a single pipe with a bender can, it really rips. i also have carbon tech reeds in my sled (its a 97 SX 700) the reeds really help throttle response
 
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SX_SLAYER said:
correct me if im wrong but dont single piped redheads make the most power around 8200rpm?



EDIT:

the 97 SX had crank problems, there are no CDI problems that i know of, and i run a single pipe with a bender can, it really rips. i also have carbon tech reeds in my sled (its a 97 SX 700) the reeds really help throttle response
Click to expand...

I'm thinking of detuning a bit. 8200 sounds so fast to an old 4 stroke wrench like me. Do these engines really stand up to such rpm's reliably?
 
Ryan B said:
700 redhead was about 110hp from the factory at 8300rpm or so. 600 was about 95 horse at a touch higher rpm.
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I must admit 8300 rpm just seems so darn fast. I'm an old 4 stroke wrench and I wonder if its possible to be reliable above 8000?
 
Might be a dumb question but how do you plan on connecting to the engine output shaft..I know nothing about ultralights but how do you plan on attaching to the tapered press fit shaft? Unless you use the original belt drive it was designed for?

By the way I think this is pretty interesting - I hope it works out for you and keep us posted!
 
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I have successfully ran 7500 miles on my 97 SX 700. The redhead, single head, triple. And no 8200 is where the engines make their most power. The redhead as you were learn most call it is probably one of the most reliable engines out there. It is factory single piped, oil injected, water cooled.

If I had my choice to keep it simple I'd find a redhead. If you get into an SRX then you are looking at the triple pipes and power valves. Same with the Viper then you also have power valves.

If I had to pick a sled to ride for the rest of my life that was 2 stroke. I'd pick the redhead I have sitting in my garage waiting to be put back together. First time I've torn it apart in 7500 miles. Ran great just figured it was maintence time. If you search around on here you will find that 10,000+ miles is not uncommon for these before guys do rebuilds. Anymore questions feel free to ask or PM me. I love the sound of a stock redhead triple spinnin 8000+ rpm.

As stated in your other thread these make about 110hp. And I see no reason it can't run 6000 rpms all day. Going down the trail we run 4000 normal get out on the lake and you run it right up there for miles.
 
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It requires a machined adaptor and the PSRU, prop reduction unit, I'm planning uses a vibration damper that connects to the adaptor. The Rotax engines are basically the same on the output end as the snowmachine versions.

Another choice uses a centrifugal clutch because the twins really vibrate at lower speeds and setup some very destructive harmonic vibrations with the prop.

There are also belt drives but I don't know about the reliability of belts at the high revs.
 
Yeah theses engines are bullet proof, and well yeah stick to red heads for your application, seeing how you are looking to 'detune' it, you won't need the extra power from the SRX or viper engines,

i tore mine apart at about 6000miles because the crank was making noise, found out later it was because my carbs froze up in the powder and it flooded the crankcase with gas so all the oil was gone, so it sounded like my bearings were going bad, THEY WERENT but we re-ringed and replaced all the bearings and it has ran like top ever since.

My dads 2000 SXR 700 had a headgasket leak and it caused antifreeze to enter the cylinder, it ate away the mag. side piston pretty badly, he replaced all 3 pistions and got a new head gasket, he still runs a thin headgasket, with no problems.
 
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