Which side of 8300rpm?

Backwoods M Max

Backwoods M Max

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Mar 31, 2011
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I got out to do some testing on my mountain Max today. After I got all the clutching put back together I was just past 8000rpm at wot. Conditions were 7-8" saturated snow at 38f and 90%+ humidity. Not a great horsepower day. I had a slight overshoot to 8200 when pinning it. Clutching is 8cr with 4.5g in both holes, wgw spring and a rx-1 helix with a green spring at 70 wrap. I'll have to test again in fluffy powder and cold dry temps.

Should i try and put 3.6g rivets in the tips to pick that 300 rpm up? From a torque curve standpoint is it better to be over or under the 8300 rpm target? The manual specifies +/- 300 rpm on that max rpm. I know today's conditions weren't the best but I'm trying to plan my next move.
 

8300 is fine... goal is 8250 to 8300... You will get a slight overrev when spinning but check it with good traction and see if it pull up as you hit top speed. You could lighten the tip if you like but I would leave it as I think it will be traction and weather dependent.
 
Thanks MrSled. I forgot to mention above that the secondary spring is original to the sled as far as I can tell (12 years old). How much of an effect will 12 years of set have on the spring and its final calibration? Could I pick up the few hundred rpm I need by going with a new secondary spring?
 
Backwoods M Max said:
Thanks MrSled. I forgot to mention above that the secondary spring is original to the sled as far as I can tell (12 years old). How much of an effect will 12 years of set have on the spring and its final calibration? Could I pick up the few hundred rpm I need by going with a new secondary spring?
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Does it have a pile of miles on it?? It could make some difference with age and use but I have a pile of old sleds and they run pretty true even with the age. What spring color and what twist is it set at?
 
Its a green secondary set at 70 degrees. The sled has about 5600 miles on it. The primary spring is brand new. Can I over spring the secondary to 80 degrees to bring the rpm up? I thought that was cheating and ended up creating efficiency losses in the clutches by causing them to fight each other.
 
You can try it...if it was me I would lighten the weight and leave the spring at 6-1. I am not clutching expert...so maybe someone else will chime in.. I havent been on them in quite a while.
 
after watching your video( good video tells alot as to whats going on) you seem to be more of a throttle jockey kinda rider((no offense intended its just how some guys ride)) meaning on and off the gas alot, not a constant run or continuing rpm so you need a fairly quick upshift and quick backshift. I would think youd be better off to use a slightly stronger primary spring to help enhance the backshift on the front clutch,your current spring is 40/114kg so you could go up to a white/white/white and that would raise your top rpm some and help backshift it a little better. the engagement will be slightly higher then what it is now. your other option is to shim your spring you have now , try 2 spring shims and see if its what you like.

if you just wind up the back spring it will backshift sooner and if you were riding in wet heavy snow i would agree that is the right thing to change but if not and it was just a 1 day thing your better off to either shim the front spring or switch to a w/w/w. You dont adjust the rear clutch to change the rpm you do it to help the engine with the load as to the snow, wether its wet and heavy needs more rear spring wrap for that day, dry poweder needs less spring wrap for that day, its somthing you can change on the fly pretty easy but usually its a 10-20 degree window as to what tunes it in and what will hurt the performance of it.

before you do anything you should take it out and run it on a normal temp(20-30degrees) snow condition day and see where your at as when its 38 out and wet snow your gonna be low on rpm from richer engine(less power) and wet snow applies more load to the clutchs via the track,harder to turn.
 
Thanks for the input mrviper700 and sorry some of our other clutching posts got so heated.

I do have a www spring I can throw in and try. Last year I was running that spring and it would have a very high engagement (5000+rpm) and coupled with a silver spring in the secondary it would never upshift. I was very much stuck in low gear. Here is my next question in this evolution.

Last year the primary was weighted backwards. 3.6 was in the heel and 4.5 was in the tip. I didn't set it up that way, it's the way it came when I bought it and the way I had ridden it until last year was a disaster and I didn't really investigate why, it's just the way it was.

Being that the tip rivet helps on top end, and heel rivet contributes to shift curve what effect does the total mass have on engagement? If I go back to a 3.6 tip, I'm at stock calibration and only changed the engagement preload and ended up with a slightly lighter total force? Does the heavier spring/heavier weights make the engine more responsive to on/off throttle riding? The field I was testing in wasn't big enough to be on the throttle long enough to fully shift out, but that was very much how I would ride out in the woods. For a day to day tuning standpoint, is it acceptable to go 10 degrees on either side of 70 degrees based on snow condition? I do have a new green spring coming so that both clutches will have new springs in them.

At the end of the day, if the www with heavier weights doesn't work I can go back to the wgw and lighten the tip. Changing a spring is easier than pulling and grinding rivets.
 
i dont understand how you could possibly have a 5000rpm engagement, as the w/w/w/ spring is 45/119kg, the spring you have in now is 40/114kg, its only 5kg differnt it might be about 300-400rpm differnt, so it will engage at 4000rpm instead of 35-3600rpm likely, but you cant get to 5000rpm with that spring unless you use a 8-10mm shim in the clutch cover(making the spring stronger because your shimming it shorter). Yamaha doesnt make a spring with more then 45kg. start. All those spring will engage right around 4000rpm. To get a 5000rpm engagement speed youd need a 55-60kg start. The less start kg the lower the engagement speed will be. Weights, and rivet placement do have a little bit of impact on engagement speed, but you cant change it a 1000rpm unless you use thick shims or go to a stronger spring start.

you do have a long spring primary clutch cover on it... right?

the reason i suggested the w/w/w/ is that its only 5kg more on the shift which will raise the shift rpm some and will backshift it slightly better. if you want more backshift it would be better to drill a hole thru the tip rivet and lighten it up a tad, go back to 4 grams. i have ran redhead engines at 8300-8500rpm and they run great anywhere in that range with the stock pipe.

its certainly acceptable and done all the time to tune the back clutch to the snow/riding conditions, usually 60-70 twist is general snow riding, if its wet and heavy snow youll need more twist like 80-90, if its glare ice you ride on and want topspeed you go lower on twist. The rear clutch is the torq. converter, it controls the shift. I like to use a spring thats soft enough to do everything I do with the sled, a red is soft, green is stiffer then red, the silver is really stiff and unless you have a roller sec., its too stiff for good snow performance, great on grass racing. I fyou find yourself having your sec spring up at 80-90 all the time like with ared for example alot of times youll find bumping up to a green at a lower twist will work better overall, as once your past 90 twist the rear clutch becomes a heat maker and will ruin your shift cirve because it wants to backshift while the front is upshifting.
If you ride like that video alot, you would really like a roller secondary clutch on that sled as it will make it more revy and very quick backshift , with a long track your not worried about top speed anyways, a roller secondary clutch would be a great improvement for you. See if hauck still makes them they go on your stock clutch and still uses the stock yamaha helix style, all youd need is that and a silver sec spring.
 
I will give the white a try this weekend. The high engagement was from last winter, but it may have been tough to truly tell the speed because there was no upshift accompanied with the engagement. The clutch would grab and engagement would go right to over revving and having to back off the throttle. We know the silver spring was the cause of that. I have a much better understanding of what it does and I need to do now than a few months ago, and way more than last winter.
 
mrviper700 said:
i dont understand how you could possibly have a 5000rpm engagement, as the w/w/w/ spring is 45/119kg, the spring you have in now is 40/114kg, its only 5kg differnt it might be about 300-400rpm differnt, so it will engage at 4000rpm instead of 35-3600rpm likely, but you cant get to 5000rpm with that spring unless you use a 8-10mm shim in the clutch cover(making the spring stronger because your shimming it shorter). Yamaha doesnt make a spring with more then 45kg. start. All those spring will engage right around 4000rpm. To get a 5000rpm engagement speed youd need a 55-60kg start. The less start kg the lower the engagement speed will be. Weights, and rivet placement do have a little bit of impact on engagement speed, but you cant change it a 1000rpm unless you use thick shims or go to a stronger spring start.

you do have a long spring primary clutch cover on it... right?

the reason i suggested the w/w/w/ is that its only 5kg more on the shift which will raise the shift rpm some and will backshift it slightly better. if you want more backshift it would be better to drill a hole thru the tip rivet and lighten it up a tad, go back to 4 grams. i have ran redhead engines at 8300-8500rpm and they run great anywhere in that range with the stock pipe.

its certainly acceptable and done all the time to tune the back clutch to the snow/riding conditions, usually 60-70 twist is general snow riding, if its wet and heavy snow youll need more twist like 80-90, if its glare ice you ride on and want topspeed you go lower on twist. The rear clutch is the torq. converter, it controls the shift. I like to use a spring thats soft enough to do everything I do with the sled, a red is soft, green is stiffer then red, the silver is really stiff and unless you have a roller sec., its too stiff for good snow performance, great on grass racing. I fyou find yourself having your sec spring up at 80-90 all the time like with ared for example alot of times youll find bumping up to a green at a lower twist will work better overall, as once your past 90 twist the rear clutch becomes a heat maker and will ruin your shift cirve because it wants to backshift while the front is upshifting.
If you ride like that video alot, you would really like a roller secondary clutch on that sled as it will make it more revy and very quick backshift , with a long track your not worried about top speed anyways, a roller secondary clutch would be a great improvement for you. See if hauck still makes them they go on your stock clutch and still uses the stock yamaha helix style, all youd need is that and a silver sec spring.
Click to expand...

It's a stock 2002 tall cover clutch. I was around 3800 grab with the w-s-w spring, I'm in the low 4000's now with the w-g-w spring. I will see how it goes with the w-w-w on engagement. Last winter it seemed over 5000. Maybe it had something to do with the clutch getting stuck in low gear because of the secondary being over sprung. I did not find any shims on the clutch cover, I didn't remember seeing any stuck to the clutch itself but I will check when I change the spring. If the w-w-w gets me where I want to be peak rpm wise, I'll live with the higher engagement when trying to start in deep snow without digging a hole. Having instant upshift will probably help a lot with digging holes. Gaining track speed faster than engine rpm should do wonders.
 
For anybody waiting for a follow up. I bought a gram scale and took .9g off the tip rivets. It was a chance to balance the weights too. I'm sure the rivets are within a tolerance when there made, but there is still variation. Started with 47.9g total weight, brought them all down to 47.0g. Picked up the few hundred rpm I was looking for. Made the sled a lot snappier too, kept my engagement around 4200 which is awesome. Now we just need some snow, we're dying here in New England for a few dumpings.
 
I had some nasty clutch vibration after I did the rivet trimming. Short of it was that the weights were out by up to .25g when weighed with a rcbs powder scale. I rebalances the weights and she purrs now. For some reason on slick ice or powder snow my rpm's dropped. Don I went back to the w-w-w primary and my rpm's are around 8300 now pinned. Engagement is around 4500. The clutch must have been excessively dirty or loading the weights with the rivets in the opposite holes last winter caused some crazy 5500 rpm engagement.

I also swapped the secondary for a new green, so both springs are new now and secondary is set at 70 degrees. I'm planning to get out on Wednesday and flog it in some deep snow and get another video of the tach.
 
Came across this thread at an interesting time. We are experiencing a bit of a warm spell and my sled reacted in a simular way. No surprise. Very informative thread.
 
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Vincent said:
Came across this thread at an interesting time. We are experiencing a bit of a warm spell and my sled reacted in a simular way. No surprise. Very informative thread.
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After going through all of this I learned 2 things. My sled can't pull a rx1 helix and heel Clickers are awesome. She runs just shy of 9000 now after full shift and pulls like an animal.
 
Better gear it higher,,,,,,,,,,, 5 mile run across a lake at 9000 grand and your done, when it will go all day at 8500......................,
 
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