Need secondary clutching advice on helix/spring

[beacon2]

Hi all,

I have a somewhat unique question that I'd like your input and advice on, since I know virtually nothing about snowmobiles. So I'll try to pick YOUR brains about what helix and spring to use.

What I have is a little racecar that I run in what's called autocross. They take an open area like part of an airport and set up orange traffic cones and make a small road course. The total length of the entire course is usually about 1/2 to 3/4 of a mile total (sometimes a little longer), with usually about 12 to 14 turns, so you can see it's fairly tight.

The speeds aren't all that fast (maybe 65 - 70 mph tops) because you're really always turning one way or the other. It's more about driver control than speed. Probably the longest stretch of straight-away is 100 feet or so to 'open her up'.

So I guess I need the driven (secondary) clutch to upshift fast and backshift fast so I can 'goose it' coming out of a corner but yet backshift quickly as I'm going into a corner to help slow it down and also be ready when I 'goose it' coming out of the corner. Does that make sense?

There's no snow or hills to contend with as a snowmobile would have, just flat concrete or asphalt with lots of turning.

The jackshaft is keyed and is 1" diameter. It currently has an old Arctic Cat button style secondary that I plan to replace with a newer style Arctic Cat roller off of Ebay fairly cheap... unless one of you guys wants to sell me yours cheap.

Any suggestions on what helix and/or spring to use?

I'd appreciate any ideas/suggestions/input you might have.

Thanks!

 

[HSR]

Really an impossible question to answer without more details.What kind of motor????Horsepower?????Rpm range????Without those details I would suggest a blue spring and a progressive helix.Now I bet your going to want more details right!

 

[beacon2]

More info

HSR,

Thank you for the reply.

The motor is a Rotax 493 l/c from a 2000 Skidoo MXZ 500. The class that I run is extremely restrictive, only the 493, the 494 (non-rave version) are legal in the class. All motors have to be bone-stock, no modifications. I've heard that horsepower on these is around 90-95, is that right?

I'm running the stock Skidoo primary clutch that came with the 493 motor. I think it has some sort of a clutch kit in it but I haven't had it apart. The guy I bought it from used said it had a kit but he didn't know or remember what it was. It was on the used motor and seems to work pretty well, although the engagement RPM is higher than I probably need.

RPM range, I'm not sure. There's no tach on it... yet. I hope to get one hooked up but I'm not sure I'd have time to take my eyes of the course to look at the tach... it gets pretty "busy" watching where I'm going.

Here's some YouTube videos that might give you a little better idea of what a course looks like. This particular course is longer than normal since it uses more of the taxi-way. They put the slalom in to slow you down some so you don't get going toooooo fast.

The first video is from the inside of another car, obviously not mine. It should give you a good general overview of the type of racing I do.
The other videos are of me but not nearly as good as the other one.

http://www.youtube.com/watch?v=gl32n7LH0pw&feature=related

http://www.youtube.com/watch?v=FR0uxmk2VOQ

http://www.youtube.com/watch?v=us4XedRLi5s&feature=related

http://www.youtube.com/watch?v=k4PxI-QPNWc&NR=1

That may give you guys a little better idea of what I need to do.

Yes, I was wondering... straight helix, progressive helix... if so, what degrees, what secondary spring, etc.

Again, thank you. I appreciate all the input and ideas that you can suggest.

 

[spring snow hero]

what do you and the car weigh? elevation? gearing? primary setup?

if you copy and paste this to the perf/mod section you will get lots o help