Hey guys I was just wondering if anybody knew what the specs are on how much to shave off on the primary clutch to get over drive. I need the spec so I can tell my machinist how much to shave off.
valin
Active member
Just wondering why you want to pull overdrive? The SRX's already pull into overdrive approx. 3% from the factory, and when you start to run more overdrive than that, you start to lose efficiency. I gear for a max of 5%.
Hey Valin ive seen your sled at the North Bay radar runs. Thats a nice looking sled and its actualy fairly slow .....lol just kinding. I've geared the sled down a tooth on the top end and was thinking get the belt in a higher ratio to make up for the gearing.
valin said:
But you've stated yourself it can work for more top end.
Also wasn't it 5% from Factory?
Ski-doo has had 18-19% O/D for years, O/D will be the secret that many want in on.
valin
Active member
There are many ways to skin a cat. On my trail sled I used to pull alot of overdrive. On my race sled, I do not pull much. You can get it to work both ways, but theoretically, you should benefit more with closer to a 1:1 ratio.
valin said:
Yes, Theoretically. Indeed there are many ways to go about this, According to some it's a waste.I'm one of the believers!
mopar1rules
Active member
yep, 1:1 is the most efficient. read in aaen's clutching book and you'll see the efficiency charts. any overdrive over 1:1, the efficiency starts to drop.
mopar1rules said:
There are still gains to be made. Valin has hit well into the 120's with a stock srx with 15% (Was it Ryan???) O/D.
I'm done here, There are many threads about this. All of which turn into arguments, and I'm not getting into it~
mopar1rules
Active member
i didn't say anything about poor top end figures...just stated it isn't so efficient.
Essarex
New member
I run an overdrive sheave (not a machined stock piece) with 23/42 gears. With my 1.25 predator, it pulls on hard pack like nothing you've ever rode. And with overdrive, I am almost back to stock gearing. I too, have read Aaen's book, but yuo have to remember that this book was published many years ago, and belt technology has improved dramatically since then. Polymer and synthetic cord formulations are more tolerant of heat and stress and I have to believe that they flex around a radius more efficiently since Aaen published the book. I have not seen a loss in top end since I added the sheave and gears, which to me indicates no material difference in clutch efficiency.
mopar1rules
Active member
i know aaens book was published many moons ago, but it has been revised here in 2007. so, if his original statement of clutch efficiency and overdrive, has changed since then, i would think that he would have changed the book then now that's its (book) is revised.
Essarex
New member
just curious, has Aaen changed his graph showing the updated losses to efficiency?
chilli
New member
Bullit01, I dont know if Ive seen your SRX before,Ill have to keep an eye out for it this year. So few SRXs around, I always notice when I see em
ohhhh noooo another war about overdrive 
Mac
Member
No No not a war just a friendly discussion among snowmobile enthusiasts. Some will say yes others will say no. Very few will even attempt an effort. I would like to prove to myself it works but don't have the timing lights to measure the results. ---mac---
bluewho
Active member
Overdrive will work if a few things are taken into consideration .Does your moter make the power to pull a higher gear top end.Do you have the right weights to push the belt higher.Will your spring compress the extra distance needed.And is the moter adjusted in the mounts properly to let the belt ride higher in the priamary.If you do it only remove the material were the clutch sheaves touch together when compressed, that way you will not lose bottom end and not take away material that is needed for support to keep from cracking.Clutch must be in good condition to do this.Do not try this on a old clutch DANGER!!!!
mopar1rules
Active member
guys, guys, guys.....i never said overdrive doesn't work, i never said that valin can't get impressive top speed #'s. i just simply said that its not as efficient as a 1:1 ratio, by looking at aaens charts/info.
Essarex, i have no idea if aaen updated his chart.
i'm not trying to argue here, or start a war
i just simply stated what i read in aaen's book and all. i'm done here.
Essarex, i have no idea if aaen updated his chart.
i'm not trying to argue here, or start a war
i just simply stated what i read in aaen's book and all. i'm done here.
valin
Active member
Gotta love how this topic always transpires....
mopar1rules
Active member
valin said:
i know....right? lol.
They never end well, I've stayed out of it for this reason!