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Discussion Starter · #1 ·
Hello,

Preface: I am designing an aircraft of 260lbs, single seat, and intend to use a MC engine. I figured the best place to get qualified info was this MC forum, as 'knowing a CBR300 is 350 lbs' is great, but fails to answer weights.

I am trying to get an engine to fit the following parameters:

Must accept the chain pulling upwards from the sprocket, so a clear path from the sprocket
Shall be of the lowest weight possible
Shall be fuel injected
Shall have between 24 and 40 HP
Shall be better in torque than in high RPM use
Shall not fall apart if operated at 75% throttle for long periods


For now I think that a Honda CRF250L, Ninja 300, or KTM 200 (not in USA?) would be contenders.

I appreciate any experienced members offering exact weights of engines (even non contenders for reference), and insight into which bikes may be good organ donors for this.

Thanks!
 

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Driftless Rider
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Interesting query, and one that takes a lot of thought.

I wonder if this question couldn't be answered better by someone on an EAA forum?

EAA Forums
 

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American Legion Rider
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I'd also think the more horse power the better to counter the effects of wind shear in case that happens.
 

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CanAm motors have been used before. They are made by Rotax. Both companies owned by Bombardier.
They were 2 strokes, and originally had carburetors. The 250cc single made around 35 hp back in the seventies.

UK
 

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Although I can't help answer any of your questions, I have often wondered why a motorcycle engine couldn't be used in an ultralight airplane. If this is what you're doing, keep us posted on your progress and any successes you encounter please. ?
 

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Discussion Starter · #7 ·
Thanks,

My motivations are based on: Desire to have the reliability found in any modern car, or motorcycle. It's a system approach. Fuel injection, amphenol connectors, engine mechanicals, leads to thousands of hours of running without shutdown. Any simple bike or car pretty much does this. Ultralights do not, engines fail, often. Then general aviation engines run lead fuel and dinosaur engines with a host of issues, so pointing back to MC, yes, that's a trouble free and affordable choice for this, add to it that MC people want light weight for speed, and the specimens become even more suited to the task. I would love to hear from folks with engines laying around, if between 200cc and 500cc what they weigh. It can help narrow down my prelim estimation that say... a honda 250 eng/radiator comes to maybe 90lbs. even if data is from random engines in that class, it is useful information.
 

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Driftless Rider
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Would you want (or need) a transmission in an aircraft engine?
The reason I ask is that most modern motorcycle engines are of "unit construction" meaning that the engine and transmission are one unit sharing a common crankcase
 

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Discussion Starter · #9 ·
Yes, While no trans would be fine, I realize lighter MC engines include the trans as unit. Props shall not go supersonic, so they are useful in a narrow range, lets say 1800-2500RPM, out of that range it's either no thrust, or prohibited overspeed, but... If I can find a gear that is geared down and suitible for takeoff at high RPM, I can shift up one once to safe altitude to reduce fuel burn for part throttle. Not driving thru the gears like some MC, nah, just using a higher gear when power not needed.
 

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Although I can't help answer any of your questions, I have often wondered why a motorcycle engine couldn't be used in an ultralight airplane. If this is what you're doing, keep us posted on your progress and any successes you encounter please. ?
If you are ever near Maggie Valley, NC, check out the Wheels through Time museum - there's a home-built airplane there, forget how old, but very, and it is powered by a HD engine, also very old.
 

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Whichever engine you get, especially a 2 stroke. Check the piston fit in the bore. What the book says, is not always what keeps the piston going up and down. Different engines and different parts, expand and contract at different rates. That is partly what throws the clearance guides out the door. Too, not all standard pistons are the same size.

UK
 

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Will have to remember Maggie Valley. I like to stop at aircraft museums. Only been to a few, but really like them. Oh, if you ever get to Hutchinson, Kansas they've got some amazing planes and rockets. The actual Apollo 13 spacecraft is there as well as a SR71.
WWII buzz bombs, copy of the sputnik satellite, while working in that area, my wife and I went several times. They are amazing places!
 

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Will have to remember Maggie Valley. I like to stop at aircraft museums. Only been to a few, but really like them. Oh, if you ever get to Hutchinson, Kansas they've got some amazing planes and rockets. The actual Apollo 13 spacecraft is there as well as a SR71.
WWII buzz bombs, copy of the sputnik satellite, while working in that area, my wife and I went several times. They are amazing places!
It is mostly motorcycles and autos - the airplane is a one-off, kept in the back, along with some other quizzical inventions. They have a web site, with some guide to what you will find there.
 

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Visionary
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That's where I saw the V twin powered airplane, Wheels through Time in Maggie Valley. In the back on the left side of the building with some other oddball stuff.

Great Museum, I love that place.

Thanks for jogging my memory!

If you are ever near Maggie Valley, NC, check out the Wheels through Time museum - there's a home-built airplane there, forget how old, but very, and it is powered by a HD engine, also very old.
 

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At to the OP, the engine in my old CB450 weighs about 85 pounds, dry, and is rated over 42 horsepower (31.33kW). That would leave less than 180 pounds for the rest of your aircraft, unless you mean it will be 260 without engine, in that case, over 345 AUW. In the model and small aircraft world, we consider 50-80Watts per pound a gentle flier, like a trainer, and 100W/lb good for some simple sport maneuvers. If AUW is 345, that old Honda engine would reach about 90W per pound. I suspect other, more modern engines of similar displacement to be in that weight to power range.
 

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Ive heard of 500 & 750cc bike engines used, but I dont have specifics.
In fact, I recall an ultralight that used a 500cc.
As a result, Id be dubious of a 350cc in an actual plane.

The Yamaha SECA 900 if the early 80s had an 853cc engine.
While I dont have the weight handy, I am capable of lifting an 853cc Yamaha engine by my self.
(Just dont make me lug if 50 yards!)
Im also in marginal shape, so the bigger engine wont cost you much in weight.
Ive hefted a few engines.

Actually I have a Honda 350cc engine kicking around.
It needs a rebuild but Ill make you a deal on it anyway.
I thinks its a tad small for your project, but if you really have your heart set on 350cc, we can deal.
 

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The OP mentioned weight is an issue.
All the older engines weigh more, for the power they are making.
All the old four stroke motors weigh more than the two stroke motors, especially when considering the power.
The OP has found newer engines that may work. I have mentioned engines that have been proven to work, as they have been used. However with one caveat. John Denver augured in. But he probably ran out of fuel.

The criteria from the OP was weight and power, not whether it could be lifted. I think reliability also needs to be considered, and it would be helpful if the glide ratio was good.

We used rubber bands before we could afford engines.

UK
 

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Ropes were used as rubber bands back in them ancient times too UK. :grin:
 
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