POLINI THOR 250

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arj1

Active Member
Joined
Jul 2, 2016
Messages
44
Location
UK
So you can spend Years building a Plane, but you don't have a couple of Days to Clean & Rebuild a Simple 2 Stroke Engine, or just take it to someone, or send it off to someone to do it for you! Actually, the whole process can be done in 3-5hrs depending on if the Cylinder needs to be Bored. Rotax 277UL's were used on 85% of the Small Kitplanes and Part 103 Ultralights so can be found all over the World. Same Engine was also used in Skidoo Sleds up to 2008. Even Shipping one from the USA/Canada isn't that much when you're looking at these New 28hp+ Engine Prices starting out at $3500+ today.
Yes, it is 5 hours for you, but a person who is not familiar with an engine rebuild it will take much longer and for quite a few is no fun at all (like for me). And 277 is no longer in production. If one designs an a/c around it, then one wants to be sure...
And around the cost - add shipping (500?) and VAT (20%) and you get around 5K right away...
It all depends! :)
 

Bille Floyd

Well-Known Member
Joined
Sep 26, 2019
Messages
558
====================================

Like I said, WHY Pay 3-4x the Cost for a Polini for only 25-36hp? If you're smarter than an 8th Grader you can rebuild a 2 Stroke. If not, you shouldn't be building an Airframe either. You can take a Skidoo/Rotax 277F/277UL to about any Skidoo Dealer or Good
...
It's the difference in weight that is my problem ; I
simply can Not use an engine that weighs over 40-Lb max.
And also:
July in Las Vegas, it is near 115-F in the shade ; I
would much rather have a liquid cooled engine. I fly
during the hottest part of the day ; it's because
that is when the thermals are Best !!

Specifications (277)[edit]
Data from ROTAX 277 UL Data Sheet[1]

General characteristics
  • Type: two-stroke air-cooled aeroengine
  • Bore: 72 mm (2.83 in)
  • Stroke: 66 mm (2.60 in)
  • Displacement: 268.7 cc (16.40 cu in)
  • Dry weight: 29.5 kg (65 lb) (complete including reduction drive and exhaust system)
POLINI THOR 202 :

Polini Engine2 stroke mono-cylinder
CoolingLiquid cooled
Bore for stroke66 x 60
Displacement205 cm3
Power33 HP
*Max trust90 Kg with Ø 130 cm propeller
R.P.M. max8.500
CylinderAluminum with Gilnisil coating
Compression ratio11,5
PistonTwo chromium plated rings mm 1
IntakeReed valve in the crankcase
CarburetorDell’Orto VHST carburetor
Air filterAir box r
IgnitionElectronic T.C.I. fixed inductive timing
Spark plug hood5 K Ω resistance
**Fuel typeE5 petrol or LL AV GAS-al with 2,5% synthetic oil 100%
*Consumption2,4 Lh at 30 Kg of static trust
Gear reduction unitHelical teeth in oil bath with 2,8 reduction ratio
StarterFlash Starter
ClutchCentrifugal in oil bath
MufflerExpansion with aluminium silencer
Engine weightFrom 16,8 Kg.
Propeller rotationClockwise
 

EzyBuildWing

Well-Known Member
Joined
Sep 23, 2009
Messages
433
Location
Sydney NSW Australia
Cuyuna 430 cc 2-stroke twin, was detuned to output 30 HP at 5500 RPM continuous reliable.......that's 14 cc per HP. Weighed 66 lbs...... = around 2 lbs/HP bare engine.
So for the Polini 300 cc, reckon on about 22 HP for similar continuous reliable.
 

Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,674
Location
AMES, IA USA
Yes, it is 5 hours for you, but a person who is not familiar with an engine rebuild it will take much longer and for quite a few is no fun at all (like for me). And 277 is no longer in production. If one designs an a/c around it, then one wants to be sure...
And around the cost - add shipping (500?) and VAT (20%) and you get around 5K right away...
It all depends! :)
==================================

Dude, I'm not going to do your homework for you, but Skidoo/Rotax's were Built & Sold in Germany and many were also Sold in many of the other 225 other countries. With the undersea tunnel from the UK to France you have access to most of Europe. The 277F came out in 1978 and was made till about 2008. So there are a lot of Engines laying around. 85% of the Ultralights and SmalI Kit Planes also used the 277UL, so many laying around. have seen Skidoo 277's sell here for $50-$200, I bought my last Good complete 277UL w/CDI with a 2.0 Gear Drive for $250. I bought a Good used 2.58 B gear Drive for $125 off eBay.

While I have found USPS usually has the Cheapest Overseas Shipping. When I checked two years ago on Shipping a RMZ-250 from Russia was around $200. It's lighter than the 277 by about 15lbs. A Complete Rotax 277 with a Gear Drive & Exhaust is 65 lbs, call it 70lbs Shipped. You don't have to buy one from the USA.

277 on eBay right now US $299.99 and Shipping from USA to UK says US $132.14 .

$299.99 eBay Engine - I was offered (4) Skidoo 277's for $50 each about 8 months ago. He wouldn't ship them and he was 5hrs away one way, so I passed. I already had 2 and probably Parts for 3rd.
$835.00 New 2.58 B Drive
$132.14 Shipping to UK from USA
$200.00 Rebuild Parts are less.
$269.00 New Exhaust off eBay.
$1,736.13 or you can spend $4000+ for a Hirth or Polini or Simonini, etc. It can be done a lot Cheaper if you SHOP around.

You have hundreds of How to Videos on Youtube, you have How to Rotax DVDs, and you have options to take it to any Rotax Service Center which there are many around the World or take it to an Ultralight Dealer or Skidoo Dealer to have them rebuild it for you., There are Sled/Jet Ski Race Shops that can also build your Engine.

Rotax Dealer Locator Map
 

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Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,674
Location
AMES, IA USA
It's the difference in weight that is my problem ; I
simply can Not use an engine that weighs over 40-Lb max.
And also:
July in Las Vegas, it is near 115-F in the shade ; I
would much rather have a liquid cooled engine. I fly
during the hottest part of the day ; it's because
that is when the thermals are Best !!

Specifications (277)[edit]
Data from ROTAX 277 UL Data Sheet[1]

General characteristics
  • Type: two-stroke air-cooled aeroengine
  • Bore: 72 mm (2.83 in)
  • Stroke: 66 mm (2.60 in)
  • Displacement: 268.7 cc (16.40 cu in)
  • Dry weight: 29.5 kg (65 lb) (complete including reduction drive and exhaust system)
POLINI THOR 202 :

Polini Engine2 stroke mono-cylinder
CoolingLiquid cooled
Bore for stroke66 x 60
Displacement205 cm3
Power33 HP
*Max trust90 Kg with Ø 130 cm propeller
R.P.M. max8.500
CylinderAluminum with Gilnisil coating
Compression ratio11,5
PistonTwo chromium plated rings mm 1
IntakeReed valve in the crankcase
CarburetorDell’Orto VHST carburetor
Air filterAir box r
IgnitionElectronic T.C.I. fixed inductive timing
Spark plug hood5 K Ω resistance
**Fuel typeE5 petrol or LL AV GAS-al with 2,5% synthetic oil 100%
*Consumption2,4 Lh at 30 Kg of static trust
Gear reduction unitHelical teeth in oil bath with 2,8 reduction ratio
StarterFlash Starter
ClutchCentrifugal in oil bath
MufflerExpansion with aluminium silencer
Engine weightFrom 16,8 Kg.
Propeller rotationClockwise
==========================

What Plane and Piot Weight are we talking about? Reduction Drive Ratio? Prop Lenght? What hp do you think you need?

The Polini Thor 250 DS Install is 55 lbs!

The Polini Thor 202 says, From 16.8 Kg = 37.03762 lbs! Why, they don't give the total Install Weight is beyond me. It has to be very close to the 250 DS. [email protected]

Hirth F33 ([email protected]) with a Muffler. Tuned Pipes are usually Lighter than most Muffler Exhausts.
Weight: 35 lbs including exhaust sys. - 40 lbs W/re-drive - 45 lbs W/elec. start! Myself, I would want Electric Start and with a Tuned Pipe vs their Muffler Exhaust, you might get it down close to 40 lbs, and can make even more hp!

Specifications (F-36) - SOLO 210 (70mm x 54mm) 207.9cc/7cc= [email protected] is possible with a Tuned Pipe and CR Bump, probably a bigger Carb needed.

A Polini 250 is (72mm x 60mm) 244.3cc and makes [email protected] 244.3cc/36hp= 6.7861cc to make 1hp.


General characteristics
  • Type: Single cylinder, two-stroke, aircraft engine
  • Bore: 70 mm (2.8 in)
  • Stroke: 54 mm (2.1 in)
  • Displacement: 208 cc (12.7 cu in)
  • Length: 275 mm (10.8 in)
  • Width: 359 mm (14.1 in)
  • Height: 341 mm (13.4 in)
  • Dry weight: 28 lb (12.7 kg) with reduction drive, exhaust system, and recoil start!
Components
  • Fuel system: 1 X integral pumper carburetor
  • Fuel type: Minimum of unleaded 93 octane auto fuel
  • Oil system: 50:1 fuel/oil premix
  • Cooling system: free air
  • Reduction gear: four element cog belt with ratios of 1.8:1, 2.0:1 or 2.5:1 available
Performance
  • Power output: 15 hp (11 kW) at 6000 rpm. Turn it 6500rpm to make more hp.
  • Compression ratio: 10.6:1 Bump CR to 11.6 and gain 1hp.


 

arj1

Active Member
Joined
Jul 2, 2016
Messages
44
Location
UK
You have hundreds of How to Videos on Youtube, you have How to Rotax DVDs, and you have options to take it to any Rotax Service Center which there are many around the World or take it to an Ultralight Dealer or Skidoo Dealer to have them rebuild it for you., There are Sled/Jet Ski Race Shops that can also build your Engine.
Sorry, still not interested.
I want something that can be bought new, assembled and supported.
 

n3puppy

Well-Known Member
Joined
Jun 25, 2019
Messages
286
===============
Did you inquire what a crate Engine Costs? Find any photos of the PTO?
Storm Lake Honda is showing a Blast in stock.

If you want any info you should call them or drive to look at it and maybe take pictures.

B5EBFE9D-BAEE-454C-806F-8BB7918FD38B.jpeg
 

sotaro

Well-Known Member
Joined
Feb 26, 2011
Messages
212
Location
San Francisco
Thank you Marc. I was more interested in the Blast 4000 going for only $1150... The thousands dollars more needed in ECU, fuel pump etc seems to encourage buying the whole sled. Armilite posted this recently. Arctic Cat Snowmobile Engine - 2021-2022 Blast 4000[

but once off into fantasy land of 177 horsepower...



QUOTE="Marc W, post: 627327, member: 46599"]
Sotaro, go to countrycat.com for the crate engines. Part# 0662-614
[/QUOTE]
 

Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,674
Location
AMES, IA USA
Are there any issues with running those high RPM two-strokes at just 50% power?
===============================

Polini's come in 33hp(202), 36hp(250), 38hp(303) I believe. So can your Plane Fly at 50%, 16.5hp, 18hp, 19hp? The Arctic Cat Blast is a 397cc Single is 65hp/2= 32.5hp. At 6500rpm with a Rotax 503 Exhaust Muffler probably about 42+hp.

It would be better to Design the Tuned Pipe for Max 6500rpm, then 8000-8500rpm! Move the Power Band down to where most Planes really Fly at 4000rpm to 6500rpm.

The 250 DS is 244.3cc making 36hp at 8000rpm = Approximatly 78% VE!

Stock Sled Engines with a Tuned Pipe fall between 93% and 95%!

Polini 250 is (72mm x 60mm) 244.3cc!

244.3 at 93% at 6500rpm = 34.8hp
244.3 at 94% at 6500rpm = 35.1hp
244.3 at 95% at 6500rpm = 35.5hp

or use the Simple 7cc to make 1hp rule of thumb when designing your Tuned Pipe. 244.3cc/7cc= [email protected]
 
Last edited:

jedi

Well-Known Member
Joined
Aug 8, 2009
Messages
3,008
Location
Sahuarita Arizona, Renton Washington, USA
I just looked thru this thread for the first time. Lots of good info here.

There is a reason for my reading. An ultralight student with a Belite powered by a Polini Thor 303 engine just went thru his third engine yesterday.

New Polini THOR 303 - PoliniThor

Post #13 of this thread has a lot of good useful information. Thanks! Based on the Post #13 information it looks to be a jetting issue but the engine was purchase new from the dealer and had the "correct" jets is my understanding.

I am intending to start a new thread for the Polini Thor 303 engine.
 

n3puppy

Well-Known Member
Joined
Jun 25, 2019
Messages
286
There is a reason for my reading. An ultralight student with a Belite powered by a Polini Thor 303 engine just went thru his third engine yesterday.
Sorry to hear your friends problems.

Polini recently had a voluntary recall on the Thor 303.
Ignition problems that let the engine start backwards.

I don't know the details- but typically means the ignition timing is firing so late that engine could run in both directions. Could be a contributing factor in your friends problems as late timing causes other problems too
 

Chip W. Erwin

Member
Joined
Feb 16, 2020
Messages
15
==========================

What Plane and Piot Weight are we talking about? Reduction Drive Ratio? Prop Lenght? What hp do you think you need?

The Polini Thor 250 DS Install is 55 lbs!

The Polini Thor 202 says, From 16.8 Kg = 37.03762 lbs! Why, they don't give the total Install Weight is beyond me. It has to be very close to the 250 DS. [email protected]

Hirth F33 ([email protected]) with a Muffler. Tuned Pipes are usually Lighter than most Muffler Exhausts.
Weight: 35 lbs including exhaust sys. - 40 lbs W/re-drive - 45 lbs W/elec. start! Myself, I would want Electric Start and with a Tuned Pipe vs their Muffler Exhaust, you might get it down close to 40 lbs, and can make even more hp!

Specifications (F-36) - SOLO 210 (70mm x 54mm) 207.9cc/7cc= [email protected] is possible with a Tuned Pipe and CR Bump, probably a bigger Carb needed.

A Polini 250 is (72mm x 60mm) 244.3cc and makes [email protected] 244.3cc/36hp= 6.7861cc to make 1hp.


General characteristics
  • Type: Single cylinder, two-stroke, aircraft engine
  • Bore: 70 mm (2.8 in)
  • Stroke: 54 mm (2.1 in)
  • Displacement: 208 cc (12.7 cu in)
  • Length: 275 mm (10.8 in)
  • Width: 359 mm (14.1 in)
  • Height: 341 mm (13.4 in)
  • Dry weight: 28 lb (12.7 kg) with reduction drive, exhaust system, and recoil start!
Components
  • Fuel system: 1 X integral pumper carburetor
  • Fuel type: Minimum of unleaded 93 octane auto fuel
  • Oil system: 50:1 fuel/oil premix
  • Cooling system: free air
  • Reduction gear: four element cog belt with ratios of 1.8:1, 2.0:1 or 2.5:1 available
Performance
  • Power output: 15 hp (11 kW) at 6000 rpm. Turn it 6500rpm to make more hp.
  • Compression ratio: 10.6:1 Bump CR to 11.6 and gain 1hp.


Would you happen to have a Polini 250DS power curve chart? Or know the HP/KW at 5,000 and 5,500 RPM?
 

Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,674
Location
AMES, IA USA
Would you happen to have a Polini 250DS power curve chart? Or know the HP/KW at 5,000 and 5,500 RPM?
===================

I have never seen a Polini 250 rated [email protected] / 250 DS 36.5hp@7500rpm Power Chart.

Both (72mm x 60mm) 244.3cc/36.5hp = 6.693cc to make 1hp! Both use 11.5cr, both use 28mm Carb.

Their Tuned Pipe was Designed for Go Kart Racing to Narrow Power Band. 244.3cc/7cc= 34.9hp@6500rpm. Most Stock Sled Engines Dial-In between 93-95% VE. 244.3cc at 93% at 6500rpm = 34.8hp.

Polini's have I think a 400hr TBO, but using them high 7500rpms, they don't last but 250-300hrs even burning 100LL from my research. They could be Improved by using the different Engine Coatings, Evans Waterless Coolant, a better-Tuned Pipe, with a better Oil. For only 34hp to 36.5hp there very Expensive.

244.3cc making 36.5hp@7500rpm = 84.5% VE!

244.3cc at 84.5% VE at 7000rpm = 34.0hp!
244.3cc at 84.5% VE at 6500rpm = 31.6hp!
244.3cc at 84.5% VE at 6000rpm = 29.2hp!
244.3cc at 84.5% VE at 5500rpm = 26.7hp!
244.3cc at 84.5% VE at 5000rpm = 24.3hp!
244.3cc at 84.5% VE at 4500rpm = 21.9hp!

POLINI 250 SPECS..jpg
 

Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,674
Location
AMES, IA USA
36.5hp = 92,871.83 BTU per hour! If you use all the Engine Coatings you can reduce your Temps by 20%. 92,871.83 BTU - 20% = 74,297.464 BTU per hour!

36.0hp = 91,599.6 BTU per hour!

35.0hp = 89,055.2 BTU per hour!

34.0hp = 86,510.7 BTU per hour!

33.0hp = 83,966.3 BTU per hour!

32.0hp = 81,421.9 BTU per hour!

31.0hp = 78,877.4 BTU per hour!

30.0hp = 76,333.0 BTU per hour!

29.2hp = 74,297.46 BTU per hour!

29.0hp = 73,788.6 BTU per hour!

HP to BTU.
 

USMC227

Active Member
Joined
Jun 5, 2007
Messages
33
=========================

Good Looks doesn't make them dependable. Doing good Maintenance and Using Good 2 Stroke Oil and using Fresh 91+ Octane Gas for 9.5cr - 10.8cr and 93+/100LL for anything higher than 10.8cr are what makes them reliable. Polini is pushing them Small CC Engines too High of rpm for Airplane use, even burning 100LL they don't last. 36hp @ 8000rpm is too High! With a 450hr TBO and used at that High rpm on Trikes they only last about 250-300hrs. Using Max 6500rpm with 93+/100LL and 40:1 Conventional Oil or 90:1 Synthetic with the different Engine Coating could extend the Engines Life. I would use the Evans Waterless Coolant also.

2 Stroke Engines Main Failures.
#1 Detonation, easy to Solve use Fresh 93/100LL.
#2 Seizures, mainly from people using Poor 2 Stroke Oils with low Flash Points.
#3 Leaking Rubber Carb Boots & Case Seals. Use the best Seals and Carb Boots. JBM.
#4 On Water Cooled Engines, Head Gaskets causing Hydro Lock. Use Evans Waterless Coolant, it doesn't Boil.
#5 Carb Ice. Install Carb Heat or use EFI.
#6 People messing with the Jetting.

A burnt Hole in the middle of a Piston is a jetting issue.

Small Pin Holes on the Piston Top or pitting around the Edges. or broken Edges of a Piston is a Detonation issue. Here is a 583 Skidoo I bought still running but with low compression on one side. This is what Detonation looks like.
Yep, this right here.
 
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