Primary clutch

[machj]

machz i was just useing that gearing as an examble i will be trying that gearing out next week

 

[machj]

snowbeast im going to cut the helix down to but im only doing one thing at a time we still have a good two to three weeks left here

 

[fourload]

Snowbeast is correct The highest it will ever come from the top is 1/4 with a machined helix. You can test this on a secure jackstand by hitting the throttle until the clutches abruptly stop,you will see that the primary sheaves hit before the belt goes to the top.Yamaha clutches just won't go to the top unless the primary and the secondary are machined like Matt from the speedshop wants to do in his clutch kit for next year.When you get your clutches machined and gear down it would be possible to use the whole primary if you shift into overdrive.However a 1 to 1 ratio is more efficient than overdrive due to a bigger contact patch for the belt on the secondary and the secondary,jackshaft and brake assembly is spinning at a lower rpm also,for a given vehicle speed, therefore using less hp.In the nutshell the sled that is geared down with overdrive will be the quicker one with the proper traction and probably faster in most trail conditions but the sled that will only shift to 1 to 1 with the taller gearing and not go into overdrive will have the ultimate top speed on ice and very long runs.

 

[ROCKERDAN]

Snowbeast is correct The highest it will ever come from the top is 1/4 with a machined helix. You can test this on a secure jackstand by hitting the throttle until the clutches abruptly stop,you will see that the primary sheaves hit before the belt goes to the top.Yamaha clutches just won't go to the top unless the primary and the secondary are machined like Matt from the speedshop wants to do in his clutch kit for next year.When you get your clutches machined and gear down it would be possible to use the whole primary if you shift into overdrive.However a 1 to 1 ratio is more efficient than overdrive due to a bigger contact patch for the belt on the secondary and the secondary,jackshaft and brake assembly is spinning at a lower rpm also,for a given vehicle speed, therefore using less hp.In the nutshell the sled that is geared down with overdrive will be the quicker one with the proper traction and probably faster in most trail conditions but the sled that will only shift to 1 to 1 with the taller gearing and not go into overdrive will have the ultimate top speed on ice and very long runs.

i totally agree...you just said exactly what i was trying to convey in different terms....

I also took everything out of the clutches and installed belt,and the belt will only ride to within about 1/4-3/8 from top of primary,do to the primary sheaves actually come together.....'

my question is,the gearing chart i use claims yamaha to have a .90 overdrive ratio,while alot of others say it will only go 1 to 1 ratio at most..have you seen the gearing chart?..here is link....i have heard guys running bigger speeds with turbos and stock gears then the 1 to 1 would allow for,so i feel the .90 is closer to correct.take alook.

http://www.snowmobileworld.com/tools/index.php



Dan

 

[fourload]

Turbo guys and asphalt racers have proved that it must have 10% with the proper machined helix. Go over to the turbo and supercharger section and check some of the speeds and posts.Our stock sleds are lucky to see 1 to 1.

 

[87gtNOS]

Dan that site you list is correct. However, I don't believe and stock Yammy clutches get more than 5% overdrive without machining.....

Use that chart for a refernce to see changes and to understand what is happening, not to be used as the 'exact' speeds, as there are many variables......

 

[the Wolfman]

...a quick end to this misery..lol...YXRC ..long or short cap.. don't close far enough to make it to the top...faces have to be shaved and moving driven has to be de-heeled....

 

[change_up]

Sorry to bring this thread back to life... but I feel it needs some attention.

Quote from a very knowledgeable drag racer over on the 2 stroke side.

Gearing and clutching go hand in hand, changing the one affects the other. When you go to a lower numeric ratio you are keeping the belt lower in the clutch and add to the efficency of the clutch system if all parts go hand in hand. So by looking at a given sled lets say with 140hp like a srx, if you run the sled at 1:1 ratio in the clutching, its going to be very efficient and transfer more of the available power to the track. When getting into overdrive on the clutch's you lose approx 10-12 percent of the clutch's efficiency, and it takes more power to run the same mph in a given distance, so in short by running in overdrive you are only applying 126hp to the clutch's by running your belt all the way up in the primary and low in the secondary. The reason for this power loss is the belt goes thru thousands of cycles of stretching and contracting and by bending the belt tighter it creates more heat from friction and contact loss, this is the lesser ability to clamp the belt from reduced belt surface to sheave contact, the smaller the bend the less area of the belt your hanging on to, now also when in overdrive your speeding up the belt. This is also the reason why the belt slips easily or burns when the sled is just starting out, you have hardly any area to hang on to the belt from the tight bend it has in the primary clutch at the beginning of shift ratio, the same thing is happening here at overdrive, just the opposite of starting out!

So what does all this mean? If you run a taller gear ratio, and you have good engine power to begin with your belt will be lower in the primary and higher in the secondary clutch at wide open, the sled will go faster from less frictional loss, but what gear ratio you can run and still maintain optimum efficiency will only be found thru testing!!


Here is a formula to play with, but you still need to test, this is just a tool to use:


Shift ratio= engine speed(rpm) x drive sprocket pitch diameter = (? ), divided by,
mph x gearing x 336


Having read this i have lost ALL confidence in overdriven clutches. You have to admit he makes a good point.

 

[black john]

o/d

my rx 1 pulls the belt within 3mm of the top with stk gearing before adding more hp and when you acount for the primary gear reduction the rx 1 was stk geared for about 120 mph. and the apex has the same gear ratio in the chain case with a deaper reduction off the primary so in therory its geared even lower. so you would have to bring the moter rpm up to about 10700 to get the clutch rpm up to pull the same gearing at the same speed.and that 120 mph was at 10500 rpm moter speed clutch rpm was still below 9000 rpm .

 

[whits-end]

Machzed and change_up are are tryin' to tell you the same thing, and it's based on fact.

Read Olav Aaen's clutch hand book. He 'splains it all. Even tho it's an old book now, physics just doesn't change.

Read the book, or else just keep tellin' each other stories.

 

[rxrider]

Meauring and math tells me stock ratio is 0.977:1 at the most. Now with an after market helix installed it will give me 0.93:1 ratio, I'll keep it that way running stock 24/38 gearing on my '03.