Primary shims

[Studroes144]

Been wanting to get the engagement up on my turbo. Using a GWG primary spring so very stiff preload but still only engaging around 3100 and I want to get it higher. I ended up cutting out some shims with our plasma cutter, the steel I used was 1.5 mm thick and I put one shin on each end of the spring so a total of 3mm. Engagement now seems to come in between 36 and 3650. No snow to try it but I was hoping for 3500+ rpm engagement. Does adding 3mm seem to make sense for gaining 500 rpm in engagement? Seems to me there'd be somewhat of a standard guideline but never researched it.

 

[staggs65]

Very rough guideline I always used was 100 rpm per mm. The rest of your primary setup affects that a little as does one primary to another.

 

[RJH]

adding shims will increase the preload and rate of the spring thru its range.

There is no "set push"..because of different spring rates and preload.

So ..when you add a shim..you have to test the pressure from the installed length to the finished length that is full comnpression..

 

[Studroes144]

Will be fun to see how this acts on long pulls, this actually makes engagement almost feel smoother..I'm sure many folks know what I mean when the rpm rises very fast from about 2600-3000, this setup gets the rpm through that range and engages very smooth still at 3600

 

[RJH]

Make sense...you have it closer to the power band.."in this case"
Your next step would be stronger helix spring then.. a higher number helix angle..

There is no end..there is no perfect setup that will last more than 3 hrs..

 

[RJH]

With 3 mm you are getting close if not for sure "spring bind"

With how the Yamaha clutch is set up I would not worry about that..probably better.

Some drag racers did that on purpose.

 

[Studroes144]

With 3 mm you are getting close if not for sure "spring bind"

With how the Yamaha clutch is set up I would not worry about that..probably better.

Some drag racers did that on purpose.

The spring bind is interesting, never thought of that. Had it out today in the back field where I've opened it up many times. 9368 rpm on the recall when rolling in to the throttle, not from a dig. 3 times in a row it hits 98 mph and feels like it hits a wall. Previous times without the shims it would run 105-110, topped it once at 113 and can only hold it for 7-800 feet tops. Will hafta pull the shims out and retry it and see if it acts different. Fresh 4" of snow over top of mud today so that could be hindering it to. Thanks for that tip tho, definitely something to keep in mind:

 

[RJH]

Been wanting to get the engagement up on my turbo. Using a GWG primary spring so very stiff preload but still only engaging around 3100 and I want to get it higher. I ended up cutting out some shims with our plasma cutter, the steel I used was 1.5 mm thick and I put one shin on each end of the spring so a total of 3mm. Engagement now seems to come in between 36 and 3650. No snow to try it but I was hoping for 3500+ rpm engagement. Does adding 3mm seem to make sense for gaining 500 rpm in engagement? Seems to me there'd be somewhat of a standard guideline but never researched it.

I bet it was nice and crisp Studroes nice backshift..

So..I have a machined scale that holds springs for measuring,,,and I graph them from that...I can change the preload and rate to any spring I have and be confident what will happen.

Here is what you can try....I forget the compressed spring length at installed..that can be found out...you also need the spec for full compressed.
So..you have the spec for installed and compressed

(I will need that soon so I hope you can help me out)

You need to find a scale and a press...with Yamaha springs a good sized drill press will work..if you get killed don;t blame me..this is for professionals only..there I said that.
So..compress the spring with the washer on to the installed length and take that reading...

You will not need to read every 10 mm like I do just go to the full compressed length or as close as you can and record that pressure..you are very near death at this point.

So..roughely you have the preload..the 1st measurement and rate the 2nd read.

Then..get the books out and find a spring with that (close to) rate and preload. I would also find one with your "liked"preload and OEM rate.

Oh what the hell..get a bunch with your preload and stronger rates..

Ask if you need to.

 

[Studroes144]

I was thinking too that I can fairly easily get the total length once installed, some readings on the micrometer and a calculator I know I can figure out installed length and collapsed length and if I'm less than the limits of the clutch travel. It's very crisp with this setup and engages just how I want it to, especially coming out on stutter. So should I be trying a longer spring with the same preload or shorter spring with same preload? If anything I'd like to lighten the weights a bit to let it rev more on top. Want it to run 93-9400 on long pulls.

 

[RJH]

I was thinking too that I can fairly easily get the total length once installed, some readings on the micrometer and a calculator I know I can figure out installed length and collapsed length and if I'm less than the limits of the clutch travel. It's very crisp with this setup and engages just how I want it to, especially coming out on stutter. So should I be trying a longer spring with the same preload or shorter spring with same preload? If anything I'd like to lighten the weights a bit to let it rev more on top. Want it to run 93-9400 on long pulls.

No ..do what I said first bud.....a longer spring will coil bind and a short will be useless. Yamaha has a huge chart of springs ...you could error on the stronger side on both preload and rate. . Aftermarket springs usually sag out in a very short time.

Do not touch the weights until we get this spring figured out ..OK? Or I cannot help you..or I cannot help if you missed that..

I don't think the turbo has the same spring as the Sr V does it? Can you find out
I will be taking my new sled clutch off soon and I can replicate your setup and test on my bench.

We will work on the secondary to get your revs up..have patience bud.

To keep your fingers out of things and busy.....find out what the stock secondary spring rate is.

 

[Studroes144]

No ..do what I said first bud.....a longer spring will coil bind and a short will be useless. Yamaha has a huge chart of springs ...you could error on the stronger side on both preload and rate. . Aftermarket springs usually sag out in a very short time.

Do not touch the weights until we get this spring figured out ..OK? Or I cannot help you..or I cannot help if you missed that..

I don't think the turbo has the same spring as the Sr V does it? Can you find out
I will be taking my new sled clutch off soon and I can replicate your setup and test on my bench.

We will work on the secondary to get your revs up..have patience bud.

To keep your fingers out of things and busy.....find out what the stock secondary spring rate is.

That all is basically what has led me to the gwg spring, strong preload and total force but not an overly long spring. I must say that after riding around for a good 5+ mins to get everything up to temp and then doing 3 back to back runs that there was no excessive heat from the belt or clutches, it ran as strong as it should right up to that 98 mph mark. You just got me thinking about the coil bind because my 800 improver ran the same as it would any other time so the shims I feel are what made the change. Secondary is completely stock with the exception I've machines the helix to get more secondary shift. Have tried straight 45, straight 47, 50/46 and 51/43 and got my revs where they needed to be and I keep going back to the stock 43, it just seems to stay the most consistent when conditions change. It really liked the straight 47 on good hard packed but hurt it more when snow got soft and heavy.

 

[RJH]

Shim = stronger spring preload and rate..I am too fussy to accept that...

after we get this spring..we will leave the 47 with a stronger spring..or you can wind the #*$&@ out of it

50 - 46 and 51 - 43 will give you more track speed on the start if you can pull it...

I will probably go with close to what you have for a primary..little less preload thou.. maybe

 

[staggs65]

you are very near death at this point.

That's too funny

 

[cannondale27]

Keep talking guys. This is what I have been waiting for. Learning for sure!

 

[Studroes144]

Shim = stronger spring preload and rate..I am too fussy to accept that...

after we get this spring..we will leave the 47 with a stronger spring..or you can wind the #*$&@ out of it

50 - 46 and 51 - 43 will give you more track speed on the start if you can pull it...

I will probably go with close to what you have for a primary..little less preload thou.. maybe

Looking on the yammi spring chart what do u think would be a good spring to try out? Got a pretty good selection of them.