A 460cc Single Dynoed using 11.0cr and a 34mm Carb.

 

Some Websites that Sell HD Racing Parts for these different Engines.

https://www.arcracing.com/billet-connecting-rods/

https://www.bullfrogperformanceproducts.com/category-s/389.htm

http://www.nrracing.com/category-s/2138.htm

 

Briggs 420.

 

Yes, gave this concept some thought, I wasn't going to mod the engine just use the Oly as a sort of 'snow tractor' and be content with 3600 rpm. But even then, I was thinking of clutching, gearing, exhaust routing, belt alignment etc, clearances etc, the cost and complications add up quickly. Really fun project though. Everything in Canada is 20-30% more expensive, an example here of a good deal of a possible engine from one of my favorite retailers:

https://www.princessauto.com/en/detail/420cc-ohv-winter-gas-engine/A-p8717639e

I was wondering about carb frosting on 4 strokes? All snowblowers have a cover that keeps the carbs warm from radiant muffler heat.

A guy in Quebec has built some low speed work machines (Yeti) using Lifan 15hp engines, they look promising:

 

Yes, gave this concept some thought, I wasn't going to mod the engine just use the Oly as a sort of 'snow tractor' and be content with 3600 rpm. But even then, I was thinking of clutching, gearing, exhaust routing, belt alignment etc, clearances etc, the cost and complications add up quickly. Really fun project though. Everything in Canada is 20-30% more expensive, an example here of a good deal of a possible engine from one of my favorite retailers:

https://www.princessauto.com/en/detail/420cc-ohv-winter-gas-engine/A-p8717639e

I was wondering about carb frosting on 4 strokes? All snowblowers have a cover that keeps the carbs warm from radiant muffler heat.

A guy in Quebec has built some low speed work machines (Yeti) using Lifan 15hp engines, they look promising:

That Sled looks nice. All these Engines 20+ different brands are all based off the Honda GX Engine Designs, so most Parts Interchange. There used on Racing Go Carts, Off Road Carts, Snow Gliders, Ultralight Airplanes, Water Pumps, Generators, etc. The Duromax 440cc, 18hp is the best bang for the Buck at $289 that I have found. Even that Engine you show isn't bad for a New Engine. Most go for $289 to $350.

Upgrades are Cheap also.

Header $45

34mm Flat Side Carb $40 (eBay)

Air Filer $35 (eBay)

Billet Rod $100 to $125

Carb Ice is a problem for All Engines, 2 or 4 Stroke. EFI eliminates Carb Icing. I bought a Ecotrons EFI kit for $300 with a 28mm Throttle Body. Mega Squirt has some cheap options to make your own kit.

Most Governors on these Engines are set at 3800rpm - 4000rpm depending on Brand of Engine. The Valves will start Floating around 4000rpm. To run Higher rpm, you need the Hi Rev kit, which entails a better HD Push Rods, HD Springs, HD Valve Locks and HD Keepers about $90 in parts. In Racing they are turning these Engine's 7000+rpm. The Highest I have seen the Airplane guys use is 6250rpm.

With these Old Sleds Gearing, I don't know what Speeds you could get with only 3600rpm. They make Comet Clutches for them. There are a couple Belt Reduction Drives for the Ultralight, Snow Glider Crowd.

Snowmobile Online Gearing Calculator

http://www.off-road.com/snowmobile/review/snowmobile-online-gearing-calculator-22848.html

What would some Old Sled Speeds be with these Engines used at 3600rpm, 4500rpm, 5000rpm, 5500rpm?

70's OLY that had a Single Cylinder?

70's TNT that had a Single Cylinder?

What Numbers would we plug into this Calc?

I recently picked up a 72 292 TNT. Still have to find a Manual for it. Got the Engine running. Seems like the Track is rubbing on the bottom of Seat, so I have a Suspension issue to solve. Don't have a Jack Lift yet. Missing the Head Light, Dash Gauges, Rear Tail Light setup, other wise in pretty good shape.

If anyone has a Diagram of the 72 292 TNT Suspension, please post a photo of it. Is their a Mod to Raise the Back End?

 

Top Speed Calculation

https://www.ibackshift.com/calculator

I found this AD for the 292 TNT said 15 to 34 Ratio.

https://itstillruns.com/specifications-1972-skidoo-engine-7828697.html

TOP SPEED USING Stock 3600rpm, then 4500rpm, 5500rpm, 6000rpm, 6500rpm, 7000rpm.

 

Trail Speeds 25mph, 30mph, 35mph by Rpm needed! Most Governors let you go up to 3800-4000rpm. Their also easy to disable.

420cc Predator Governor Removal & Performance Mods.

 

420cc Predator Stage 2 Engine Build ~ Billet Rod, Billet Flywheel & Performance Cam.

This guy also has some nice Video's on these Honda/Briggs/Clone Engines.

How to Modify Honda Gx390 cylinder head! ACTUAL SPECS!

 

Ok, now you're getting me hooked! I supposed to be re-insulating my attic this summer (knee walls etc yuk) not modding my ski-doo!

I think my 12/3 engine is getting weak, last summer when I took the muffler off I could see there was some melting at the top ring (3 rings) and some scoring, compression was still around 100 psi. So have to decide, refresh the top end maybe plane the head a bit or replace with a used engine like a 335 or even a 399 twin, they pop up here once an awhile.

Just finished this project, get some cycling in without getting stuck or falling on my butt. Works to some degree, I take it drifting on the local skating rink, until I run out of breath.

 

Clutching and the right gearing. There have been many 4 stroke mods on the old sleds. KISS is the idea. Not meant for high performance, just reliability. Remember many old sleds had Koehler 4 strokes. If I was to doo it, I would go with a Honda. No brainer there

 

Ok, now you're getting me hooked! I supposed to be re-insulating my attic this summer (knee walls etc yuk) not modding my ski-doo!

I think my 12/3 engine is getting weak, last summer when I took the muffler off I could see there was some melting at the top ring (3 rings) and some scoring, compression was still around 100 psi. So have to decide, refresh the top end maybe plane the head a bit or replace with a used engine like a 335 or even a 399 twin, they pop up here once an awhile.

Just finished this project, get some cycling in without getting stuck or falling on my butt. Works to some degree, I take it drifting on the local skating rink, until I run out of breath.

working.jpg

It would be Cheaper to just Rebuild your 12/3 and do a few Cheap Upgrades!

Your 12/3, was I think 12hp@5500rpm, (76mm x 66mm) 299.5cc, used a Low 6.5cr, and probably used a small 28-30mm Carb. The later 300 (76mm x 66mm) 299.5cc, was 15hp@5500rpm using 7.0cr. maybe a bigger Carb.

General Rule: +1.0cr = 2hp, so +.5cr = 1hp. Try to verify both Engines Rpm Ratings and Carb Size used to make that 3hp difference!

There is a difference in the Standard Muffler vs the TNT Muffler. Tubes are Bigger, and maybe Insides have bigger Baffle Holes. If your handy with a Welder, Grinder, Saw, you could upgrade your Muffler to TNT Spec's or add a Tuned Pipe.

Upgrading the Carb to a 32-34mm Flat Side $40 off ebay would be a good Improvement. With a Bigger 32-34mm Carb you maybe able to turn it higher 6500rpm also.

Milling the Head for 91 Octane say 11.5cr, IF +1.0cr = 2hp, 6.5cr to 11.5cr = +5.0cr x 2hp = 10hp

K&N Air Filter. Never seen a Dyno Test to see what if any a better Air Filter will make. But if an Engine can't breathe it can't make more Hp.

 

Clutching and the right gearing. There have been many 4 stroke mods on the old sleds. KISS is the idea. Not meant for high performance, just reliability. Remember many old sleds had Koehler 4 strokes. If I was to doo it, I would go with a Honda. No brainer there

Honda does make the best Engines, but their 3 times the cost also, plus any Mods.

 

Trail Speeds 25mph, 30mph, 35mph by Rpm needed! Most Governors let you go up to 3800-4000rpm. Their also easy to disable.

Unless someone has completely changed the drive train of your 72 TNT (track and sprockets) your GEAR/RPM/MPH speed numbers are wrong.

Almost all pre-80's Ski-doo tracks are 1.97 pitch not 2.52 that you used in your calculations.

That means MPH will be roughly 78% of what you show.
Example 25.6 x .78 = roughly 20 mph

 

Unless someone has completely changed the drive train of your 72 TNT (track and sprockets) your GEAR/RPM/MPH speed numbers are wrong.

Almost all pre-80's Ski-doo tracks are 1.97 pitch not 2.52 that you used in your calculations.

That means MPH will be roughly 78% of what you show.
Example 25.6 x .78 = roughly 20 mph

Ok, that makes sense. The Calc didn't offer that choice below in the list for 1:1 (9) Tooth Sprocket. Any Idea How they figure that Constant Value Number that we could just plug it in? I like how you can compare multiple Gears Sets or different Max Rpm Speeds on one page. In the mean time I'll look for a different Calc that may work with these Older Sleds. I did write the guy and ask him to include the Old 1.97 Pitch.

Do the 70's Ski Doo's all have (9) Tooth Drive Sprockets or does that Number very also?

I found the different Gear Ratio's used on a 71 Oly as 15/34(300). 15/35(335), 16/34(399). A 71 Elan 10/25(250). A 71 292 TNT as 15/34 and the 340-S TNT as 16/34.

 

Here is a Calc that doesn't ask for Track Pitch 1.97 or a Constant. The Gears 15/34 = 2.27 Ratio. The Gears 15/35 = 2.33 Ratio. The Gears 16/34 = 2.13 Ratio. Don't know the Driver Dimensions in Inches. I counted 9 Tooth in the photo. Anybody know that Answer? My Sled is buried at the moment behind a bunch of stuff so I can't go measure it. Can these different Drive Sprockets be Interchanged? If so, what Sizes are available?

MPH Calculator

http://racenssr.com/calc.htm

What IF with a 4.5" Driver.

The Gears 16/34 = 2.13 Ratio at 3600rpm with a 4.5" Driver = 22.6mph.

The Gears 16/34 = 2.13 Ratio at 4500rpm with a 4.5" Driver = 28.2mph.

The Gears 16/34 = 2.13 Ratio at 5500rpm with a 4.5" Driver = 34.5mph.

The Gears 16/34 = 2.13 Ratio at 6500rpm with a 4.5" Driver = 40.8mph.

--------------------------------------------------------------------------------------------------------

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 4.5" Driver = 21.2mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 4.5" Driver = 26.5mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 4.5" Driver = 32.4mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 4.5" Driver = 38.3mph.

---------------------------------------------------------------------------------------------------------

The Gears 15/35 = 2.33 Ratio at 3600rpm with a 4.5" Driver = 20.6mph.

The Gears 15/35 = 2.33 Ratio at 4500rpm with a 4.5" Driver = 25.8mph.

The Gears 15/35 = 2.33 Ratio at 5500rpm with a 4.5" Driver = 31.6mph.

The Gears 15/35 = 2.33 Ratio at 6500rpm with a 4.5" Driver = 37.3mph.

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

What IF with a 5" Driver.

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 5" Driver = 23.5mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 5" Driver = 29.4mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 5" Driver = 36.0mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 5" Driver = 42.5mph.

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

What IF with a 5.5" Driver.

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 5.5" Driver = 25.9mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 5.5" Driver = 32.4mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 5.5" Driver = 39.6mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 5.5" Driver = 46.8mph.

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

What IF with a 6" Driver.

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 6" Driver = 28.3mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 6" Driver = 35.3mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 6" Driver = 43.2mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 6" Driver = 51.1mph.
=============================================================

What IF with a 7" Driver.

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 7" Driver = 33.0mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 7" Driver = 41.2mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 7" Driver = 50.4mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 7" Driver = 59.6mph

 

Off eBay, VINTAGE SKI-DOO 9-TOOTH DRIVE SPROCKET P/N:572010200 NEW OLD STOCK looks to measure 5.0" in photo.

So with a 5" Driver.

The Gears 15/34 = 2.27 Ratio at 3600rpm with a 5" Driver = 23.5mph.

The Gears 15/34 = 2.27 Ratio at 4000rpm with a 5" Driver = 26.2mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 5" Driver = 29.4mph.

The Gears 15/34 = 2.27 Ratio at 5000rpm with a 5" Driver = 32.7mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 5" Driver = 36.0mph.

The Gears 15/34 = 2.27 Ratio at 6000rpm with a 5" Driver = 39.3mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 5" Driver = 42.5mph.

The Gears 15/34 = 2.27 Ratio at 7000rpm with a 5" Driver = 45.8mph.

 

Even these Small Harbor Freight 212cc Predator Engines rated 6.5hp@3600rpm with some Mods they can make 15-20hp would be nice for a kids Sled. When they go on Sale for $99. These are being used on some Ultralights today used at 15hp@4400rpm.

1st Trials 212cc Clone in Direct Drive.

Upgraded his Clone Engine to Belt Reduction Drives.

Same guy with original Rotax 185's 9.4hp@5000rpm.

 

Ok, that makes sense. The Calc didn't offer that choice below in the list for 1:1 (9) Tooth Sprocket. Any Idea How they figure that Constant Value Number that we could just plug it in? .

I see you already found a different calculator.

If you would have looked further on the website you linked for the original calc, you would have seen the author gave instructions on how to calculate the drive sprocket constant.

Text of the example pasted below - just start out with 1.97 instead of 2.86 in the first equation and solve the rest.

https://www.ibackshift.com/calculator

How to calculate a drive sprocket constant
Here is example of skidoo 2.86 pitch track with 7 tooth. You can replace the numbers with your own details.
The formula is also in Aaen clutch tuning manual.
When you scroll down the page, you will eventually see a chart with all the constants.

(2.86 pitch x 7 tooth driver) / 12 = X
(60 / 5280) = Y
(x)* = Z

1/z = Constant

Therefore - (X = 1.67)*(Y = 0.01137) = 0.0189

1/0.0189 = 52.6651 (52.66)

Constant = 52.66

 

I see you already found a different calculator.

If you would have looked further on the website you linked for the original calc, you would have seen the author gave instructions on how to calculate the drive sprocket constant.

Text of the example pasted below - just start out with 1.97 instead of 2.86 in the first equation and solve the rest.

https://www.ibackshift.com/calculator

How to calculate a drive sprocket constant
Here is example of skidoo 2.86 pitch track with 7 tooth. You can replace the numbers with your own details.
The formula is also in Aaen clutch tuning manual.
When you scroll down the page, you will eventually see a chart with all the constants.

(2.86 pitch x 7 tooth driver) / 12 = X
(60 / 5280) = Y
(x)* = Z

1/z = Constant

Therefore - (X = 1.67)*(Y = 0.01137) = 0.0189

1/0.0189 = 52.6651 (52.66)

Constant = 52.66

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.

(2.86 pitch x 7 tooth driver) / 12 = X
(60 / 5280) = Y
(x)* = Z

1/z = Constant
Therefore - (X = 1.67)*(Y = 0.01137) = 0.0189
1/0.0189 = 52.6651 (52.66)
Constant = 52.66

------------------------------------------------------------------------

(1.97*9)/12 = 1.4775 (X)

(60/5280) = 0.0113636363636364 (Y)

(X) 1.4775 * (Y) 0.0113636363636364 = (Z) 0.0167897727272727

1/0.0167 = 59.88023952095808 (59.88)

Constant = 59.88 <==== My Math maybe wrong!

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

The Gears 15/34 = 2.27 Ratio at 4000rpm with a 5" Driver = 26.2mph.

The Gears 15/34 = 2.27 Ratio at 4500rpm with a 5" Driver = 29.4mph.

The Gears 15/34 = 2.27 Ratio at 5000rpm with a 5" Driver = 32.7mph.

The Gears 15/34 = 2.27 Ratio at 5500rpm with a 5" Driver = 36.0mph.

The Gears 15/34 = 2.27 Ratio at 6000rpm with a 5" Driver = 39.3mph.

The Gears 15/34 = 2.27 Ratio at 6500rpm with a 5" Driver = 42.5mph.

The Gears 15/34 = 2.27 Ratio at 7000rpm with a 5" Driver = 45.8mph.

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.

 

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

 

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.

 

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.

 

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.

 

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.

 

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.

 

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.