79 scorpion tk 440 drag sled

[heiner921]

i guys. im looking a making my scorpion tkx 440 into a drag sled. anyone have a good setup that worked for them? did you use a comet 102c clutch? whats spring? different size gears? any info is helpful.

[obj1]

Tk's are family trail sleds, not racers. What are you thinkin?

[mooreperformance]

Probably not much help but doesn't the TK have the standard Whip exhaust? I would think that going to the Sting exhaust would give you a HP increase at high rpm?

Testing is your best way of increasing performance. Adjust the drive clutch so it just reaches maximum closing at the end of the race track (belt at the top of the sheaves). This is a combination of weights, springs and gearing. This is the best way to utilize all of the gearing built into a variable speed clutch while traveling down a race track.

I would think that the guy that would have the fastest Scorpion would be the guy that can convert a modern secondary (driven) clutch to a Scorpion chain case. A lot of tuning is done with an adjustable secondary (driven) clutch.

It would seem that Scorpions really are at a disadvantage when it comes to driven clutch technology. No adjustments can be made (at all) to a Scorpion driven clutch.
Driven clutch cams and spring tensions are the key to getting a Comet Drive clutch to work well! Installing a Cat driven clutch (somehow) would be the way to go!

From my experience it seems that the Scorpion drive clutch is closing much to soon. The torque converter locks up way to early!
The Scorpion racers are relying on engine torque to accelerate the sled. Not good.

The best clutch would allow the engine to immediately spin up to max RPM (max horsepower) and the gearing (clutch action) should accelerate the sled.

The perfect racer would max out, with the belt at the top of the drive clutch and at the bottom of the driven clutch (maximum clutch gearing), at the very end of the track. This would be the top speed and would also utilize all of the gearing advantage that the clutch could provide along the course of the track.
Just my two cents.
Dennis

[obj1]

I never thought we were at a disadvantage. Most times when we leave the track its the yamaha guys, the mercury guys and the rupp guys that think there at a disadvantage. lol

[scorp11]

The 79-81 440 TK's had the Sting pipe and a Mikuni Carb. The Scorpion TK's do real well around here in the stock classes.

I don't think you'll have an issue with the secondary in the stock classes, may want a 102C comet primary for tuning purposes.

[obj1]

So scorp11, is the sting pipe thing good or bad? You mean we could have the wrong pipes? No wonder why these things are slugs.

[scorp11]

Jan 11, 2013 22:35:41 GMT -5 obj1 said:

So scorp11, is the sting pipe thing good or bad? You mean we could have the wrong pipes? No wonder why these things are slugs.

The Sting pipes are terrible. You should never run them. I'll take all the ones you have so that you don't have to worry about them collecting dust. The only thing worse are some twin pipes I recently saw on some TK. I suppose if I "have" to, I'd take them too

[mooreperformance]

The Sting pipe is a good thing Scorp 11 is just joking.

I was told (back when I was a dealer) that they were good for a substantial horsepower increase at high rpm.
When we asked why they weren't standard equipment on all Scorpions we never got an answer!
I guessed (at the time) that they (maybe) cost a little low speed torque. So the pure trail sleds used the standard exhaust.

The main difference between the Sting and the Whip exhaust was the "Y" pipe (manifold). The Sting was a true "Y" and the Whip was a simple "y". The Sting manifold had a pronounced division between the cylinders with equal length pipes. The Whip was designed/compromised for a more compact/space saving manifold/exhaust.

Pararailer has a TK with the Whip exhaust system.

[mooreperformance]

When I worked as a snowmobile mechanic for a John Deere dealer we were given a warranty kit to install on the John Deere Cyclone (440RV Fan Cooled CCW). It consisted of different clutch weights and a new spring (Comet Drive). When it was installed on the sleds it helped performance some. When we installed it with a new 41 degree driven clutch cam and stiffer driven clutch spring, those sleds were much faster. The steeper cam angle allowed a faster up-shift and faster back-shift.

That little experience really hit home with me and made me start thinking about driven clutch tuning. Most sleds do well with a 34 degree driven clutch cam (Scorpion) and the standard spring. BUT, when you start tuning clutches for high elevation and deep powder (like we do in California), the driven clutch spring tension/cam ramp angle is very important! I can't help but to think that this is also very important in re-tuning a snowmobile clutch/carburetor for grass/hot weather drag racing.

Just to be able to play around with spring tension on the secondary would be an eye opener (I think) for a Scorpion racer.
A stiffer spring tension would hold the drive clutch in low gear a little longer and probably boost acceleration slightly. This would keep the clutch from shifting out too soon and lugging the engine. So important!


I am sure the most important part of drag racing is making sure that the clutch is fully shifted out and that maximum engine rpm is attained at the very end of the course. Knowing where the engine makes max horsepower (6500 rpm for an example) and changing the gears in the chain case for maximium rpm (when the clutch is fully shifted out) at the very end of the course is the basic start to tuning a clutch and finding the correct sprockets (gear ratio).

If the clutches shift out too soon and the sprocket gearing doesn't allow the engine to reach maximum RPM you are throwing away a lot of performance because you are not utilizing all of the gear multiplication available to you from a variable speed transmission.
Unfortunately...you can get max RPM from your engine at the end of the track if the clutches stay in low gear! But you are not going to win.

Everything needs to come together just as you are crossing the finish line...maximum engine RPM and the clutches fully shifted out into high gear (just like drag racing a car!)

[heiner921]

Well i have the sting pipe so thats a plus.... still need more insite on clutching and gearing...