Yamaha Clutching.

[philsummers21]

Have some questions for a clutching guru if theres any out here. I need a few more RPMs out of my Nytro and i believe it falls off to much between the trail and Deep snow. Maybe its a 4 stroke thing tho. Anyways what does winding up the secondary spring accomplish? More aggressive backshift im assuming but does it gain you rpms as well? How about the primary spring. Does running a stiffer primary spring gain or loose you rpms? and im not sure on how to read a yamaha spring yet. Im use to ski-doo springs there easy (130/320). Also does it matter where you add or loose weight to your weights? and whats the advantage of adding weight to the tip or heal? Thanks in advance Phil.

1 more question. What would going from a Green/white/green to a Orange/pink/orange spring accomplish

 

[Turk]

Go to the technical pages & read thru the clutching section. It,s all there.this stuff has been answered a lot of times in the last 6-8 years on this website. The clutching section in the technical section explains how everything works.

 

[philsummers21]

Thanks Turk ill check it out. I must have went to the wrong spot earlier. all i could find was a list of what people were running for different sleds

 

[philsummers21]

Ok heres a question. If i tighten my secondary spring i should gain more RPMs and Backshift sooner correct?

 

[spray25]

Ok heres a question. If i tighten my secondary spring i should gain more RPMs and Backshift sooner correct?

Yes. Typically you want to controll RPMs with the primary, however, the MTX has rather poor backshift stock.

 

[philsummers21]

And to gain rpms in the Primary i can do a few things. higher final force spring, Loose weight, or shallower helix. If i go a higher spring what else will that accomplish? if i go lower weight i don't pull as hard correct?

 

[Turk]

You want to lighten primary weight to gain rpm,s. Adding a stiffer primary spring makes the weights work harder to overcome the force. For deep pow riding it,s nice to have a slight overrev for better backshift(9000 rpm) It will bang off the rev limiter on hardpack tho at wot. It is impossible to get both hardpack & deep snow clutching at the same optimum rpm,s on these sleds.

 

[outofbounds]

You may want to call Tom Hartman. I think he fits under the "guru" category. Good guy who will take time to talk with you. He can also provide the custom clutch parts if he has what you need.

208-468-1073

 

[outofbounds]

You may want to call Tom Hartman. I think he fits under the "guru" category. Good guy who will take time to talk with you. He can also provide the custom clutch parts if he has what you need.

208-468-1073

 

[yamahaboy701]

Tom Hartman and Turk are both clutching gurus! I have Tom's Nytro MTX clutch kit and it works great does exactly what turk suggested above "slight overrev for better backshift(9000 rpm) It will bang off the rev limiter on hardpack tho at wot". On the trails I see 9200-9400 and about 8800-9000 off trail.

 

[philsummers21]

Thanks to all the responses above. I know it may sounds stupid but i try to derive at my own clutching instead of buying a kit. I would really like to learn the ins and outs of clutching.

I do understand that ill need to overrev on the trail but as yamahaboy said he looses about 400rpms from trail to pow. Im loosing about 1000-1200. Ill try to twist my secondary a little more see what that gives me.

 

[Stoli]

get this book - everything you could possibly want to understand about the clutching. Even then there is a lot that goes into the understanding of it even with the book... rider weight, conditions, any other mods, track.... so there will be some trial and error involved with weights and springs and preload as you indicate. I just got back from MT and i was only getting 8400 in the powder while similar Nytro's were pulling 8800 with similar clutching setup - but the difference in track, weight, springs and i have 900 miles vs the others having 200 miles on it.... so even i still have some tweaking to do before the next trip.

http://www.amazon.com/Olav-Aaens-clutch ... B0006R954Y

 

[philsummers21]

yah i just ordered that book yesterday.

 

[Mtnviper]

Phil
Moving mass (rivits) to different hole positions effects rpms at givin point in the shift.
For example my sled was over-reving at slow speeds and under-reving at 60-70 mph. 9200 lower speeds dropping to 8500ish. So I removed 2.1 grams from the tip, and added 2.4 to the heel and another .3 to the center.
The shift is 8800-9000 straight through now! (I run a little higher rpms then stock, because of the Excell header.)
Weights with more mass in the heel will usually back shift better, pull harder at low speeds, but may not have as much top speed.
Heavy tips are good for top speed (as long as the motor can pull the rpms), but can have a lazy back shift.
Another factor is how much track you have. Big ol mountain tracks can rob a lot of horsepower at higher speeds, pulling the rpms down. So a good mountain set-up will usually be heavier in the heel and lighter in the tip.

 

[philsummers21]

Ok went to 30 degrees on the Arctic Cat yellow spring and wow. 8400 rpm trail/deep/hills all day long today i was 8400. Backshift was incredible. Going to shave a gram off the tip of my weights to try to get 200 more RPM out of her. But i must say this sled ran awesome today. Even impressed some XP800s and M8s. Actually walked all over the m8 but his clutching was way out.