[sightation]

Yes, there is a Formula below to figure the Drive Constant, but if you don't know those Old Skidoo's actually used a 1.97 Pitch, and it was not even given even as a choice below, it doesn't do you any good. Did all the other Brands of Sleds also use the same 1.97 Pitch back then also? The other Calc is simpler to use once you know the Driver OD in Inches. Don't have a Aaen Clutch Manual.

2nd Clac Says:
So with a 5" Driver.
The Gears 15/34 = 2.27 Ratio at 3600rpm with a 5" Driver = 23.5mph.
1st Calc says using 15/34 Gears an 59.88: At 3600rpm = 26.5mph

So we got a Slanted photo that looks like 5.0", but could be 5.125" which would affect the Numbers. Just 5.0" vs 5.125" Driver at 3600rpm would give you 23.5mph vs 24.1mph. So having the exact Driver OD Measurement would be nice.

Using the 5.0" Driver, 15/34 Ratio and 23.5mph at 3600rpm, the other Clac Constant would have to be 67.5 to equal same Speed.

Looking at sprocket diameter is not the best way to figure distance/MPH. Especially on hole and tooth type tracks. (convolute) Too many variables such as track thickness change the effective diameter of the sprocket vs the actual measured.

However pitch x teeth gives an exact measurement of how far the track/sled will move for every revolution of the sprocket. (Assuming no slippage on ice etc)

1.97 inch pitch x 9 teeth = 17.73 inches of ground travel.

Therefore 17.73 inch "effective" circumference of the sprocket means 5.64 "effective" diameter.

Plug that into your calculators and what do you find at 3600 rpm?

Calculator 1 - 1.97 pitch, 9 teeth - 26.5 mph
Calculator 2 - 5.64 diameter - 26.6 mph

The 0.1 difference? - rounding error of the calculators

 

[RotaxFlyer]

Looking at sprocket diameter is not the best way to figure distance/MPH. Especially on hole and tooth type tracks. (convolute) Too many variables such as track thickness change the effective diameter of the sprocket vs the actual measured.

However pitch x teeth gives an exact measurement of how far the track/sled will move for every revolution of the sprocket. (Assuming no slippage on ice etc)

1.97 inch pitch x 9 teeth = 17.73 inches of ground travel.

Therefore 17.73 inch "effective" circumference of the sprocket means 5.64 "effective" diameter.

Plug that into your calculators and what do you find at 3600 rpm?

Calculator 1 - 1.97 pitch, 9 teeth - 26.5 mph
Calculator 2 - 5.64 diameter - 26.6 mph

The 0.1 difference? - rounding error of the calculators

So for Old Skidoos 1.97 Pitch, 59.88 is the right Constant to use. Thanks. So your saying the Actual Size of the Drive Sprocket is 5.64" not 5.0" or are you basing that Spec off the Speed of the 1st Calc? I can live with a +/- 0.1 mph. Just knowing what your Approximate Speed should be is nice.

 

[RotaxFlyer]

The fellow who made the 1st Calc says 1.97 pitch Speed Constant is 59.56 for 1.97 Pitch.

https://www.ibackshift.com/calculator

He sent me a Simple Excel Spreadsheet, which I just Duplicated for multiple Rpm's. This Site won't let me upload it here.

Also, the Guy who had the Drive Gear on eBay wrote back and said it was exactly 5.0" OD.

 

[whirli]

bringing this old topic back up... i've got a 12/3 that runs perfect, and a 69 SS 370 opposing twin. we've had both in my family since new. the issue with both is that i don't dare go further than eye sight of the house. the 370 has always been either really fun, or not running at all. Currently it doesn't run.

to throw another wrench into all of this, i'm waiting for those new single ski widescapes WS 250's to hit the market and potentially pick up their drive train in them for someone who does a 2-stroke swap. 20hp, EFI 250cc 4-stroke.

Another new option is the 212 predator Ghost. Supposebly a 6500rpm engine with around 16hp from the factory.

 

[sightation]

bringing this old topic back up... i've got a 12/3 that runs perfect, and a 69 SS 370 opposing twin. we've had both in my family since new. the issue with both is that i don't dare go further than eye sight of the house. the 370 has always been either really fun, or not running at all. Currently it doesn't run.

to throw another wrench into all of this, i'm waiting for those new single ski widescapes WS 250's to hit the market and potentially pick up their drive train in them for someone who does a 2-stroke swap. 20hp, EFI 250cc 4-stroke.

Another new option is the 212 predator Ghost. Supposebly a 6500rpm engine with around 16hp from the factory.

Wondering why you don't just fix the 370 it so it is reliable vs swapping engines?

And why a 4 stroke instead of something like a plain old Doo 320 or 335 single?

20hp WS250 is liquid cooled so swap will be a little complicated but is designed for snowmobile type duty.

 

[whirli]

Wondering why you don't just fix the 370 it so it is reliable vs swapping engines?

And why a 4 stroke instead of something like a plain old Doo 320 or 335 single?

20hp WS250 is liquid cooled so swap will be a little complicated but at least it is designed for snowmobile type duty.

View attachment 2012005

Main reason, i'm not very resourceful and i have no clue on where to find parts to rebuild this older stuff. track/suspension.... yeah Kimpex, everything else seems to be a black hole.

good point on the liquid cooled, you saved my future self a good half hour of head scratching in the garage thinking.... "cripes, now what"

 

[Lucas123]

For general parts contact GB Distribution on Face Book. He's great to deal with. Here is an Elan repowered with a 420 cc from Princess Auto, he uses a Comet 206095A clutch for the 1" engine shaft. Still that engine on salel is around $300 here (Canada) plus another $300-400 for the clutch + taxes, so worthwhile to keep the Rotax engines running! Fun to do though.

 

[Lucas123]

A family member gave me an old 5800 watt generator that had been sitting for years, got it running but no power. After a lot of testing I decided to scrap the generator but keep the motor (Lifan 188f) as it seems really good. Problem with generator engines is the short tapered crank end so I saved about 4 inches of the rotor shaft and welded it back on. Now the whole shaft is about 1 1/4" when I need 1" so I ground it down by holding an angle grinder in a vise and turning the engine with a drill or wrench

. After about 2 hours I got it quite straight but still have to do the keyway. My neighbours love me... So now that I have a spare motor I'll never need it.

 

[RotaxFlyer]

For general parts contact GB Distribution on Face Book. He's great to deal with. Here is an Elan repowered with a 420 cc from Princess Auto, he uses a Comet 206095A clutch for the 1" engine shaft. Still that engine on salel is around $300 here (Canada) plus another $300-400 for the clutch + taxes, so worthwhile to keep the Rotax engines running! Fun to do though.

===================================

You forget to make these Honda/Clones Bullet Proof to turn them up to 5500rpm, you still need to Upgrade the Internals, Billet Rod, and Billet Flywheel, and to make more hp a better CAM, a Higher CR, a Bigger Carb, K&N Airfilter, Tuned Header Exhaust. A 460 Single made 37.37hp@5000rpm. Harbor Freights 459 Single is $499.99. If you do all the Upgrades you're looking at about $600 = $1,099.99. Then you have to buy the Comet Clutch $369+ = $1,468.99.

Most of these Old Skidoo Singles can be rebuilt for less than $200. You can do some Trail Porting by Widening the Port to 65% of the Bore. You can have the Head Machined or Machine it yourself to raise the Low CR, you can Bolt on a Bigger Carb. I recently bought a 38mm Mikuni Flat Side off eBay for $81.You can Bore the Cylinder for an even bigger Carb if needed. You can Bolt On a better Exhaust Muffler. You can also Adapt or Build a Custom Tuned Pipe for even more hp. Hp Cost $$$.

28mm Carb = Area 615.752 sq mm.

30mm Carb = Area 706.858 sq mm.

32mm Carb = Area 804.248 sq mm.

34mm Carb = Area 907.920 sq mm.

36mm Carb = Area 1017.876 sq mm.

38mm Carb = Area 1134.115 sq mm.

39mm Carb = Area 1194.591 sq mm.

40mm Carb = Area 1256.637 sq mm.

41mm Carb = Area 1320.254 sq mm.

42mm Carb = Area 1385.442 sq mm.

43mm Carb = Area 1452.201 sq mm.

44mm Carb = Area 1520.531 sq mm.
---------------------------------------------------
Stock 335 SINGLE Intake Port 25.6mm x 47mm = 1183.134 sq mm.

335 Intake Port - Ported 25.6mm x 51mm = 1285.534 sq mm.
---------------------------------------------------
Stock 340 TnT SINGLE Intake Port 29mm x 47mm = 1363.0 sq mm.

Stock 340 TnT SINGLE Intake Port - PORTED 29mm x 51mm = 1479.0 sq mm.

 

[sightation]

Here is an Elan repowered with a 420 cc from Princess Auto, he uses a Comet 206095A clutch for the 1" engine shaft. Still that engine on salel is around $300 here (Canada) plus another $300-400 for the clutch

Don't have to buy a new Comet clutch for these Conversions.

Golf Cart folk have been adapting clones for some time. They have 3/4 and 1 inch Straight shaft to 30mm taper Adapters so you can use a std Snowmobile clutch.

Grab a swap meet Duster for cheap and put in some more pucks and lighter spring for 3600rpm operation. - Just like the Comet 206095A

 

[Lucas123]

Cool, thanks for the info; this would reduce the cost of the retrofit considerably.
I doubt I would remove the governor on this engine (Lifan 188f / GX390 clone) ; the expense of modify it to safely spin faster is a bit much. GX390 specs show 11.7 hp at 3600 and 19.6 ft lbs torque at 2500 rpm so dialing in the clutches and even the chain sprockets to capitalize on that torque would be important get any even Elan 250 top speed.

 

[raphelanss]

 

[raphelanss]