# Anyone deviate with their engine choice?

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#### Jeff Higgins

##### Active Member
I ask because I recently obtained a very nice two cylinder Suzuki 2 stroke engine in a snowmobile that runs excellent and is light weight. I believe it’s rated at somewhere around 25hp and I’d love to use it on the minimax that I’m going to be building. I only see mentions of Rotax and Hirth engines being used though. Am I overlooking something?

#### TFF

##### Well-Known Member
Rotax and Hirth made ready to run airplane engines. Some people convert them on their own but they have to come up with a gearbox or belt drive to do it.

#### n3puppy

##### Well-Known Member
A lot of the snowmobile engines would be ok for use in a ultralight. That's the way it was done way back then in the 80's.

Like TFF said Rotax and Hirth just made it easier by coming out with flight specific stuff like gear boxes or belt drives.

To keep your Mini-max under legal ultralight weight (254) you will need to be sure the engine is light enough. Most of the folks I flew with back in the day used 277 Rotax singles on their Mini-max, Hi-Max etc. and built real light. (Delete stuff like engine cowls and wheel pants)

Your challenge would be to take your 25hp Suzuki, figure a way to add a belt drive to reduce prop RPM and keep the weight of the total package - carb muffler etc. low enough to make legal weight.

I see Team currently uses the 28 hp Hirth motor in the Minimax 103 and just makes weight at 250lbs. So your target would be the 35 lbs of that engine including belt drive and muffler with maybe a few lbs extra ok depending on how light you can build the airframe.

Do you know the model number of the engine? Or what sled its in? Might be some info out there on the specs - With weight, and HP at what RPM being very important numbers.

#### Jeff Higgins

It’s a 1978 Arctic Cat Lynx 2000t. I couldnt beat the price of $200 for the complete sled and running engine. I’m not worried about the redrive system because I’m a gunsmith and machinist so I’ll be making one to fit. Also from what I’ve read online, this particular engine is really easy to squeeze more hp out of with a larger carb and a mild porting job. I’ll likely be doing that. At the moment I’m trying to source the cheapest wood that I can to get this done as a budget build, as ultralights were originally conceived back in the day. #### Turd Ferguson ##### Well-Known Member I ask because I recently obtained a very nice two cylinder Suzuki 2 stroke engine in a snowmobile that runs excellent and is light weight. I believe it’s rated at somewhere around 25hp Is it the 440cc engine? As long as you're not trying to make Part 103 empty weight it should work. #### Jeff Higgins ##### Active Member No, it’s only 275cc but very lightweight if I remember the weight I found online. #### n3puppy ##### Well-Known Member It’s a 1978 Arctic Cat Lynx 2000t. I couldnt beat the price of$200 for the complete sled and running engine. I’m not worried about the redrive system because I’m a gunsmith and machinist so I’ll be making one to fit. Also from what I’ve read online, this particular engine is really easy to squeeze more hp out of with a larger carb and a mild porting job. I’ll likely be doing that. At the moment I’m trying to source the cheapest wood that I can to get this done as a budget build, as ultralights were originally conceived back in the day.
Ok -the 275 engine is rated at 22hp at 5500 rpm. The 340 version of that motor is rated at 35hp at 6500 rpm. 340 is basically the same just bigger bore.

Just based on those numbers - yes looks like you could probably do a little porting to bring the rpm up to 6500 and gain a few HP. OR... maybe find some 340 parts and take it to the full 35hp

Might be a good idea to talk to Team and see what they feel is minimum hp for their part 103 model before you go planning a bunch of engine mods as anything you do will put more stress on the engine. 5500 rpm is a nice number if that would be enough HP.

#### Dana

##### Super Moderator
Staff member
Very few minimaxes even with the 277 make legal weight. It's not impossible, but few manage, or even worry about it.

#### poormansairforce

##### Well-Known Member
I had a Kaw 340 on mine and wasn't legal. Wouldn't want any less than 35 hp.

#### proppastie

##### Well-Known Member
Log Member
Ok -the 275 engine is rated at 22hp at 5500 rpm
not a sled person......does that 5500 rpm direct drive the track? I might be looking for a 6000 aprox. rpm 20 hp engine direct drive as I am limited in prop size to 32".....

#### Jeff Higgins

##### Active Member
Yes that’s directly from the crank.

#### Armilite

##### Well-Known Member
not a sled person......does that 5500 rpm direct drive the track? I might be looking for a 6000 aprox. rpm 20 hp engine direct drive as I am limited in prop size to 32".....
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No, Sleds use Clutch's and Gearing with Chain. No Sled that I know of is Direct Drive!

20hp x 7cc = 140cc for 6500rpm. That's using 11.5cr and a Tuned Pipe.

To make 20hp at 6000rpm would take 150cc, using 11.5cr and a Tuned Pipe.

My 1976 Arctic Cat JAG 2000 275 F/A is rated 20hp@6000rpm, 340 was rated 30hp@6000rpm both with a Muffler.
275cc/20 = 13.75cc to make 1hp with a Muffler.

Rotax 185UL = 184cc
Skidoo 250 = 247cc
Kawaski 250 or 292 Single (Nikisil)
JLO/Rockwell & Sachs made about 15 different Singles 100cc to 395cc all with Mufflers. They have (4) Threaded Holes on PTO Case to mount a belt drive. Probably the ACE could be retrofitted to work. PTO Drawings on the Web for the JLO's. Some JLO's the Sleeve can be taken out and Nikisiled for a +5mm in Bore and Save on Weight.

#### Armilite

##### Well-Known Member
The JLO/ILO L-152 is still made New, for Garden Tillers, I think it was \$369. It comes with a Small Mikuni Carb today. For Airplane use it needs a Bigger Carb, Porting, a Tuned Pipe, maybe a +CR Bump.
(59mm x 54mm) 147.6cc rated 5.7hp@4500rpm. 147cc/7cc = 21hp

Niksiled +5mm (64mm x 54mm) 173.8cc. You could go Bigger! Some of these sharded the same Case and Cranks are swappable for different Strokes. NOS JLO parts on ebay.

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#### Armilite

##### Well-Known Member
I ask because I recently obtained a very nice two cylinder Suzuki 2 stroke engine in a snowmobile that runs excellent and is light weight. I believe it’s rated at somewhere around 25hp and I’d love to use it on the minimax that I’m going to be building. I only see mentions of Rotax and Hirth engines being used though. Am I overlooking something?
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Which one of their Planes are you talking about? 1100R Mini-Max|1030F Max-103|1500R Sport|1550V V-Max|1600R Sport
1650R Eros|1700R Hi-Max|AeroMax SuperMax?

What different Engines have other People been putting on it?

Just about any Small 2 Stroke can be built to make 25hp to 50hp. What HP do you really need? 25hp x 7cc = 175cc+, 50hp x 7cc = 350cc+ if using 11.5cr and a Good Tuned Pipe.

Plane Empty Weight + Your Weight + Fuel Weight + Bags Weight converted to KG, then divide by 10kg = kw needed to be converted to hp. Or you can use MTOW, say if 600lbs = 272.2 kg / 10kg = 27.2 kw = 36.5 hp needed.

A Hirth F-33 (28hp) with a Belt Drive is 20 lbs lighter than the Rotax 277UL with a Gear Box..

#### proppastie

##### Well-Known Member
Log Member
No, Sleds use Clutch's and Gearing with Chain. No Sled that I know of is Direct Drive!
The picture I saw of just the engine it looked like a variable drive pulley on the crank.....one where one side of the cone shaped pulley goes in an out and the diameter of the pulley changes.....but I really do not know how it is setup.

147cc/7cc = 21hp
do you have a reference for that...how do you figure it.

A Hirth F-33 (28hp) with a Belt Drive is 20 lbs lighter than the Rotax 277UL with a Gear Box..
do we know if the Hirth can run direct drive....maybe you said there was a prop hub for the crank, but I can not remember.

#### Jeff Higgins

##### Active Member
I know you’re referring to the other guy, but what I meant is the hp rating is from the crank alone. Sleds do have a variable drive like a cvt transmission. As for a prop hub, in a machinist so I’ll be making my own reduction drive and hub for the engine I have.

#### mullacharjak

##### Well-Known Member
Isnt 250cc too small for a minimax.I think 340cc would be a better option.I was thinking of useing an 800cc 1/2vw engine but that too is 25 hp and I doubt if it would work.

#### pictsidhe

##### Well-Known Member
I know you’re referring to the other guy, but what I meant is the hp rating is from the crank alone. Sleds do have a variable drive like a cvt transmission. As for a prop hub, in a machinist so I’ll be making my own reduction drive and hub for the engine I have.
Designing a reliable redrive is no simple task. If you think it is, you don't understand what needs to be addressed.

#### Jeff Higgins

##### Active Member
You’re definitely underestimating my talents.

#### pictsidhe

##### Well-Known Member
You’re definitely underestimating my talents.
What is the most difficult aspect of a reliable redrive?