Machine Primary to get the belt all the way to the top

[TurboJamie]

Another one for you experts it seems and so I have been told that the belt never comes to the top of the primary clutch is this true? If so can the clutch be machined to allow it to close further and shift out more?

 

[tonykof]

I've noticed this on mine too. I'll be courious to the answers.
tk

 

[rxrider]

With a stock primary, and a stock helix in the secondary the belt is not getting all the way to the top at full shift out. It will stop 7 millimeters from the top with a new belt in. If you use a aftermarket helix which is machined to reach overdrive you will get the belt up 3 more millimeters. If you do not have a after market helix in you can put little 1.5 mm washers on the bolts before you put the helix back on. To get the belt all the way up you need a speed sheave like Hauck sells, or you can buy the Yamaha 88R sheave out of a Viking III any year, remember to balance the sheave before you install it, there is some extra aluminum on the back side on the outer edge that has to be ground away or else your clutch will be out of balance and maybe hurt the bearings in the engine drive shaft. You may also tear down your primary and mill away a little at the bottom of the sheaves but that will weaken the clutch sheaves some. I DO NOT recommend it. If you are going to mill them down anyway. First place a new broken in belt at the top of the sheaves flush with the outer edge. With the primary spring out, move the movable sheave completely towards the fixed sheave and measure the gap you get, holding the belt close to one of the sheaves, between the other sheave and the belt. You will find the distance the sheaves need to be milled to lift the belt all the way up. Mill half the measured distance from both movable and fixed sheave.

 

[LightningPro]

I would like to provide some information for you guys who want to modify your clutches for overdrive. If you like it fine ,if you don't thats fine too as I am not looking for any arguments especially because I am just trying to be helpful. I have been doing the primary clutch mod for overdrive since 97 on our sleds and many customers clutches in conjunction with our Lightning Pro Roller Secondary.

Earlier clutches in 97 thru 99 seemed to have a weaker casting, prone to fine hairline cracks near the center. I haven't seen any cracking in the last couple of years unless the person had his clucthing way off and caused a lot of heat, and that was before I took it apart to do the mod.
I haven't had any of the clutches blow apart that I have ever modded.

If you are bound and determined to do this yourself, here are the specs that I use.

1. The clutch must be dissassembled so that the split collar ring can be machined down .022. If you machine your sheaves and not the split collar you will be starting your shift engagement with a gap which will give you a jerky engagement and your sheaves will not close as far they could/should for this mod

2. While chucked up in a lathe, machine off .019 from each sheave contact surface near the center (NOT the whole angled face)

3. Blend/machine a radius so that the flat contact face that you just cut blends into the angle of the sheave.

4. Re-assemble clutch and balance (VERY IMPORTANT). Balance as a complete clutch but without the weights installed. I spotdrill on the backside like factory to balance -remember the inner sheave is rotated to a new position if the spit collar is machined.

5. On the secondary, machine .125 off the face of the hub where the helix inner hub would come to a bump stop. This is very hard steel under the aluminum casting and requires carbide to machine. Keep in mind that certain springs will coil bind and aren't designed for the extra travel.

This is not a mod that every one can or should do themselves. Dont do it if you cannot do all the steps listed above.

Also this mod doesn't really affect the take-off and lower speeds if that is what you are looking for, only the top-end. If you sled is not topping out or running out of gear this won't make a difference. To make use of this modification you should consider gearing down. You will get up to speed quicker and still have the topend from the overdrive mod. This is the real advantage to this mod!

I hope this helps if you are going to do it or at least lets you know what is involved.

Bob Flores
Lightning Pro

 

[Silverbullet]

Great rite up Bob....I would sugest that if you feel the need for speed than I would turn the BOOST UP

 

[rxrider]

LightningPro - thanks for the info on the correct way of dooing this mod.

 

[evil eagle]

I would like to provide some information for you guys who want to modify your clutches for overdrive. If you like it fine ,if you don't thats fine too as I am not looking for any arguments especially because I am just trying to be helpful. I have been doing the primary clutch mod for overdrive since 97 on our sleds and many customers clutches in conjunction with our Lightning Pro Roller Secondary.

Earlier clutches in 97 thru 99 seemed to have a weaker casting, prone to fine hairline cracks near the center. I haven't seen any cracking in the last couple of years unless the person had his clucthing way off and caused a lot of heat, and that was before I took it apart to do the mod.
I haven't had any of the clutches blow apart that I have ever modded.

If you are bound and determined to do this yourself, here are the specs that I use.

1. The clutch must be dissassembled so that the split collar ring can be machined down .022. If you machine your sheaves and not the split collar you will be starting your shift engagement with a gap which will give you a jerky engagement and your sheaves will not close as far they could/should for this mod

2. While chucked up in a lathe, machine off .019 from each sheave contact surface near the center (NOT the whole angled face)

3. Blend/machine a radius so that the flat contact face that you just cut blends into the angle of the sheave.

4. Re-assemble clutch and balance (VERY IMPORTANT). Balance as a complete clutch but without the weights installed. I spotdrill on the backside like factory to balance -remember the inner sheave is rotated to a new position if the spit collar is machined.

5. On the secondary, machine .125 off the face of the hub where the helix inner hub would come to a bump stop. This is very hard steel under the aluminum casting and requires carbide to machine. Keep in mind that certain springs will coil bind and aren't designed for the extra travel.

This is not a mod that every one can or should do themselves. Dont do it if you cannot do all the steps listed above.

Also this mod doesn't really affect the take-off and lower speeds if that is what you are looking for, only the top-end. If you sled is not topping out or running out of gear this won't make a difference. To make use of this modification you should consider gearing down. You will get up to speed quicker and still have the topend from the overdrive mod. This is the real advantage to this mod!

I hope this helps if you are going to do it or at least lets you know what is involved.

Bob Flores
Lightning Pro

I had .018 off of each sheave but I did'nt take the clutch apart, just had it machined. I had it done thsi way with my last two apex's. The first one I put 22700 miles on it that way, so I think there is no reliability issues.

 

[HURRICANE]

We are doing the overdrive clutch mod a bit different.We are also machining the split collar and where the sheaves meet.Then we are SLIGHTLY changing the angle of the sheaves to less angle to ride the belt up higher.This mod is invisable and will hold up on 400hp engines while racing or trail with no adverse affects

 

[Grimm]

What kind of prices are people paying for such a mod?