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What are Shims

22K views 14 replies 5 participants last post by  TINKEN 
#1 ·
I have been looking at clutches trying to figure out what I'm going to get and one thing I notice that keeps popping up on the forums are shims for the clutch. What is the purpose of the shims and what benefits do they add as far as performance and reliability?

thanks,
 
#2 · (Edited)
#3 ·
I send a pm to Todd seeing if sold them without buying his sheave kit haven't heard back yet
 
#5 · (Edited)
Hunterworks does sell them separate, they are an OEM Yamaha part.

If Todd doesn't have the size you need, I have them as sets of two for 3 bucks, both in 18-8 stainless steel at 0.2mm and 0.5mm because nobody's output shaft is the same and often requires fine tuning to shim the desired width. Pretty simple, just don't want to run out of splines at the end of your shaft and you don't want to hit your spider/belt cover, hence the fine tuning. Easier with Hunterworks sheave because there is no grease cover on the end of the clutch. :icon16:


 
#6 ·
^ how much you think would be good to add to a shock (mm) sheave Micheal?
 
#8 ·
If your belt doesn't rise too far out of your secondary clutch to rub on your belt case, I have seen additions between 0.5-1.8mm (2.2mm for me because I don't use a cvt cover).

For lack of better pictures, these will have to do. Notice there is a space between the outside belt surface and your cvt cover. You need to keep your outer belt from rubbing that case by adjusting your shim count.

Here is with no shims:


Here is with some shims:


Here is with maximum shims:


It's a really inexpensive mod, but it will take a little bit of Tinkering with to get the most out of it. Your belt moves lower in the primary and higher in your secondary clutch, therefor yielding lower take off torque. :icon16:
 
#7 ·
Here's a few more pictures to explain the process. Lower take off, even in high range puts less stress on your belt and wet clutch. For me, I like the reliability this gives and don't care about a few mph extra that I probably won't use anyway.

Without shims:



With shims:

 
#14 ·
Shims added to a stock clutch (1.5mm), no machining to allow the belt to run to the top of the primary. But there's an added amount of bottom end. With a machined clutch, belt travel is both lower and higher.

https://www.youtube.com/watch?v=ngS2sJaeIAU
You said the 1.5 mm shim on a stock clutch allows the belt to run to the top of the primary, actually just shims on a stock clutch it would run lower on the primary and higher on the secondary and decrease top speed but agreed more bottom end.

That is why the machined sheave is the better mod all be it more money but you lose nothing.

Im not writing this to you, it was to anyone reading your comment I am pretty sure you mean secondary and typed primary.

Todd
 
#15 ·
I meant that since the sheave in the video is stock, there is no machining to allow the belt to run to the top of the primary sheave. As seen in the video, the belt is down 0.25" from the top.

The shims in conjunction with a machined sheave is a better mod when applicable. For instance if you have over sized tires, you are likely not going to be able to use your top speed and tuning your clutch for a little more bottom end would be to your advantage.
 
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