Lets all fix this Crappy clutching once and for all

[Rx1M5]

OK I've got an idea here that if everyone buys into we can make some headway on this MTX clutching. From talking with other guys on here I don't believe most guys are getting the full potential out of the primary clutch on these sleds with any of the setups listed. I have put a magic marker line on my primary from the outside edge to the center hub. After riding I still have pretty well 3/4 of an inch showing on the line measured from the outer edge of the primary to whats left of the line and the rest is rubbed off. If everyone does the same thing we can get some real numbers on the primary and belt height. I don't believe most gys belts are going as high as they say because I've looked at a bunch, but the only way to know for sure is to measure them.

If we can get full shift out I think we all should be able to see 48+ mph track speed in a real pull, I'm not talking hard pack here.

So slap on a mark and post your true results including your clutching setup.

48 gram base weight Heavy hitters loaded to 51.3 grams all in the heel
14.5 rollers stock primary spring G/W/G
Yellow Cat spring at 10 degrees 39 Helix still
156 2.5 15 Camo extreme.

Rx1M5

 

[ben apexgt]

i was looking for the same problem on my apex gt and it was recommend to shave on both sheave (primary) .010 and test it with a black marker to see how far it goes and may be another .005 if not enough to get the maximum range anything for the secondary ???

 

[Rx1M5]

Are you talking about milling the sheaves? My Rx turbo runs the same primary clutch and the belt goes to within 1/8" on the primary, mind you its got the power to do it, anyways I think the clutch has the ability to fully shift out mines just not doing it.


Rx1M5

 

[Nikolai]

stock 8FS weights with 17.2 rivets in all 3 holes
not sure on rollers but GWG primary spring
stock pink driven spring at 100* with 39 helix
150x15x2.5
20/40 gearing
with the permanent marker test I'm about 3/4" from the top of the primary.

I'm trying the YWY spring next weekend which has a little lower rate than the GWG (24.5 vs. 27, same 45 preload).

 

[Rx1M5]

If you haven't changed the rollers from stock you have 16.5's. The 14.5's offer more belt squeeze with less total weight in the primary. Lots of guys, myself included the rollers are the first thing changed in the primary. I've always been led to believe that the lighter you make all your clutching components the more reactive your clutch setup will end up being which if you think about it makes sense cause more weight needs more Hp to make it work.

Rx1M5

 

[ruffryder]

Rx1M5... I think you are confused a little. Achieving full shift out is a function of hp and gearing. We do not have the hp to achieve full shift out with 20/40 gearing as turbo sleds are running 80 - 90 mph track speed with that setup.

I am pulling 47-48 mph trackspeed.

Supreme tool adjustable weights supertips, 7g base, 1g middle, 1g tip
16.5 rollers, orange pink orange primary spring (30/137)
18/42 gearing
Camoplast challenger 153x2.25 track
modified stock header, under tunnel exhaust.

running 8600 rpms, I need to increase them to about 8900 or so, but I am lazy, even though the supertips are really easy to use.

 

[Rx1M5]

Rx1M5... I think you are confused a little. Achieving full shift out is a function of hp and gearing.

I'm aware of that but this setup and HP should be capable of moving the belt higher in the primary. I forgot to mention I'm running 19/40 gearing. Have you put a marker line on your primary and measured truly how far up you are getting. My sled will pull over 50 mph on a good pull in low snow (9" or so) but the belt still only goes to within 3/4" of the top of the primary, so track speed is not the only measuring stick. Belt movement is the only easy way to compare dissimilar setups and conditions. If we could line up 10 different setups at the same place on the same day then we would know what does and doesn't work but there are so many other factors like snow depth, snow type, elevation etc etc. My Rx1 stock (140hp) used to put the belt right to outer edge of the same primary so the Nytro should be able to as well. IMO this isn't a HP issue as my Nytro is probably making 10 more HP than my Rx1 did before I turboed it.

Rx1M5

 

[macnytro]

does the 14.5 rollers work better on a stock nytro then the 16.5. this sled has a pipe & power commander on it & clutches are stock but i added 13.3 steel w/hole in outer but still hits rev. limiter on hard to soft snow unless it's real deep snow than not to bad

 

[Rx1M5]

In theory you should be able to get away with less weight with the 14.5 rollers, but weight curvature plays a big part in that as well. The stock Nytro weight is very flat and bulky. IMO adding more weight to that already heavy weight isn't the way to go. I'm only running if I remember right 77 grams in my turbo sled and its pushing over 260 hp so the little Nytro shouldn't need that much weight. JMO.

Rx1M5

 

[Tookes]

In theory you should be able to get away with less weight with the 14.5 rollers, but weight curvature plays a big part in that as well. The stock Nytro weight is very flat and bulky. IMO adding more weight to that already heavy weight isn't the way to go. I'm only running if I remember right 77 grams in my turbo sled and its pushing over 260 hp so the little Nytro shouldn't need that much weight. JMO.

Rx1M5

BTW, what RPM's are you getting?

 

[skidooboy]

if you want to see how much you can possibly get for a shift out on the belt, take out the primary spring, close the sheeves till they bottom, place belt in the primary. that is all you get without machining the faces of the bottom contact area of the sheeves.

most yamahas i have ever saw or worked on could only get to about 3/8" from the top of the sheeves. i believe this is max shift. to get more you have to cut the primary.

 

[Rx1M5]

In theory you should be able to get away with less weight with the 14.5 rollers, but weight curvature plays a big part in that as well. The stock Nytro weight is very flat and bulky. IMO adding more weight to that already heavy weight isn't the way to go. I'm only running if I remember right 77 grams in my turbo sled and its pushing over 260 hp so the little Nytro shouldn't need that much weight. JMO.

Rx1M5

BTW, what RPM's are you getting?

I'm getting right around 8650 but it is rock solid.

Rx1M5

 

[MAMILLA]

Rx1M5... I think you are confused a little. Achieving full shift out is a function of hp and gearing.

I'm aware of that but this setup and HP should be capable of moving the belt higher in the primary. I forgot to mention I'm running 19/40 gearing. Have you put a marker line on your primary and measured truly how far up you are getting. My sled will pull over 50 mph on a good pull in low snow (9" or so) but the belt still only goes to within 3/4" of the top of the primary, so track speed is not the only measuring stick. Belt movement is the only easy way to compare dissimilar setups and conditions. If we could line up 10 different setups at the same place on the same day then we would know what does and doesn't work but there are so many other factors like snow depth, snow type, elevation etc etc. My Rx1 stock (140hp) used to put the belt right to outer edge of the same primary so the Nytro should be able to as well. IMO this isn't a HP issue as my Nytro is probably making 10 more HP than my Rx1 did before I turboed it.

Rx1M5

Hey what track are you running? Because I heard it is good to go with 19 top gear, but I am still running the 153" track.

 

[akvector]

Not to compare apple to oranges but My buddy in his mxz is running 18/45 gears and 9 tooth drivers and that thing just rips. Same with his rev 600. I have no doubt that his 600 with kick the snot out of my nytro.


Here is my delima. I have always geared down on all of my yamahas but I have never been able to get the track speed that I would expect. I have never been happy with my vector and my nytro does not do what I expect either. I have a hard time spending 10gs and have to dump more in to make it work.

 

[Rx1M5]

Doo has always used those large diameter drivers thats why their bottom gears are so large. The final drive between the two systems Yami vs Doo isn't really much different. The thing that the large drivers are nice for is they have less track bend and they have slightly less resistance as well. I don't know if that actually gives any more power but they never ratchet.

Rx1M5