Well I searched and searched for a way to get my 96 Vmax engagement significantly above 4000 RPM, and even on this site I never found anything. It's probably not a big deal for a stock engine because the low end has plenty of pull, but mine was piped and it always bothered me that I couldn't get the engagement high enough to be useful. I know there are others out there in the same situation. I took out the pipes long ago but I still wondered about the clutch spring issue.
The short answer is, even though these are "short cover" primary clutches you can use "tall cover" primary springs, you just have to do some complicated math to convert the forces to the smaller clutch. I was pretty sure of my math but I needed to do extensive testing and now I can say for sure, on a 96 Vmax STW where the stock spring is (O-P-O) 90501-605J5-00 you get the same shift-out force with the long spring (Y-S-Y) 90501-582L1-00 and this spring will give you a much much higher engagement, almost 5000 RPM on the stock engine.
Now, do I recommend this? I can say that switching from a straight helix to the 51/39 made a bigger difference than raising the engagement. Something like 47/39 might be better for this model (mountain max) but what I'm using has performed much better than stock (night and day) in every condition and in every way, so I can't complain and I won't be changing it again.
This 600 has a lot of low-end for a piston-ported engine, so I'm not sure how much I've gained by raising the engagement. If my engine was still piped it would be an absolute necessity, but on the stock engine it just winds up a little faster and pulls just a little harder at first, but the difference is not huge. But I won't be switching it back either.
http://www.totallyamaha.com/snowmobiles/aaTECH/drivespecs/primary_springs.htm
Remember that you are squeezing "long tower" springs into the "short tower" clutch, so the pressure specs need to be converted. Both the preload and the full shift will end up higher than the spec sheet. It's a little too complicated for me to type the formula, but it can be done. The key to the formula is knowing what the tower size is, and I don't know if I have it down to the micron but the math worked out close enough with the tall cover at 73.66mm and the short cover at 65.4mm. With those numbers you can use the above chart to convert long spring specs to how they will perform in a short tower. As long as you get the full-shift KGs to match closely to stock, everything will be the same except for the higher engagement, and since we are using long springs in a short tower, all these spring will raise your engagement.
Anyway if anyone wants more detail or direction on this feel free to PM me, I'm not a big regular on this site but I'm a Yamaha owner and I'll try to help.
The short answer is, even though these are "short cover" primary clutches you can use "tall cover" primary springs, you just have to do some complicated math to convert the forces to the smaller clutch. I was pretty sure of my math but I needed to do extensive testing and now I can say for sure, on a 96 Vmax STW where the stock spring is (O-P-O) 90501-605J5-00 you get the same shift-out force with the long spring (Y-S-Y) 90501-582L1-00 and this spring will give you a much much higher engagement, almost 5000 RPM on the stock engine.
Now, do I recommend this? I can say that switching from a straight helix to the 51/39 made a bigger difference than raising the engagement. Something like 47/39 might be better for this model (mountain max) but what I'm using has performed much better than stock (night and day) in every condition and in every way, so I can't complain and I won't be changing it again.
This 600 has a lot of low-end for a piston-ported engine, so I'm not sure how much I've gained by raising the engagement. If my engine was still piped it would be an absolute necessity, but on the stock engine it just winds up a little faster and pulls just a little harder at first, but the difference is not huge. But I won't be switching it back either.
http://www.totallyamaha.com/snowmobiles/aaTECH/drivespecs/primary_springs.htm
Remember that you are squeezing "long tower" springs into the "short tower" clutch, so the pressure specs need to be converted. Both the preload and the full shift will end up higher than the spec sheet. It's a little too complicated for me to type the formula, but it can be done. The key to the formula is knowing what the tower size is, and I don't know if I have it down to the micron but the math worked out close enough with the tall cover at 73.66mm and the short cover at 65.4mm. With those numbers you can use the above chart to convert long spring specs to how they will perform in a short tower. As long as you get the full-shift KGs to match closely to stock, everything will be the same except for the higher engagement, and since we are using long springs in a short tower, all these spring will raise your engagement.
Anyway if anyone wants more detail or direction on this feel free to PM me, I'm not a big regular on this site but I'm a Yamaha owner and I'll try to help.
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