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First two pictures are of my factory sheave , the second two my coops sheave , don’t know if it helps any but may give something to the discussion 🤷🏼‍♂️
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To actually understand the benefit of machining you have to see the different wear marks after machining, where the belt rides in a closer position to the center of axis.
 

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Back to basics, shim widens the distance between sheaves so the belt rides closer to the shaft center of axis. We machine the sheave (remove material) to provide the same result, let the belt down in the primary further...closer to the center of axis.
To the thread starter, it looks like the machining was done near the outer edge of the sheave face with nothing done near the center of the sheave, so the ratio is close to stock.
The stock sheaves shown above look to have a straight surface contour, the sheave being thicker at the center and thinner near the outer edge. The discussion starter sheave is dished, with a curved/dished sheave face....not the machining theory needed for best results.
COOP reduces the seal hump to let the belt ride closer to the center of axis for a higher pulley ratio and better low end pull.
 
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Looks like your guy only took off a mm.. That's not enough to notice.
You may have something else going on as the belt should be running a little closer to the center.
It is a bad idea to run staggered roller weights. That may also be part of your problem.
I’ve got a photo of mine it doesn’t quite look like your stock sheave View attachment 100407
 
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Discussion Starter · #25 ·
Well I believe we’ve all came to the conclusion they did very little machining if any and I agree that they have no clue what they were doing .. I’d like nothing more then to take it back to them and have them redo it , I have talked to them and all they say to me is they took the 1.5 mil off already if I’d like more it will cost me another $300 bucks !! I don’t think so , if I decide down the road to go farther into this I’ll buy new sheaves and have coop45 do it . For now I’ll just shim the hell out of it ,what ever I can get out it before something rubs Thank you to everyone for the info
 

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If you haven't do your self a favor and service the secondary and install all one weight rollers like 18's or 20's
 

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I’ve got a photo of mine it doesn’t quite look like your stock sheave View attachment 100407
From looking at your photo it looks like the belt has ran closer to the seal hump than most stock sheaves do. Did they do any machining on the inside of the sheave where the roller weights sit?? Kinda like in this photo?? Right Hand sheave.
 

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In post #3 he said inner and outer sheaves got machined.
Maybe machining of the weight channels in the movable sheave and face machining on the fixed sheave....who knows?
 

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Discussion Starter · #29 ·
From looking at your photo it looks like the belt has ran closer to the seal hump than most stock sheaves do. Did they do any machining on the inside of the sheave where the roller weights sit?? Kinda like in this photo?? Right Hand sheave.
No the inner roller channels were not touched
 

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Discussion Starter · #30 ·
In post #3 he said inner and outer sheaves got machined.
Maybe machining of the weight channels in the movable sheave and face machining on the fixed sheave....who knows?
Yes the movable and fixed got machining they didn’t do anything inside the primary, they said .75 mil of each sheave to make 1.5
Also I’ll add when everything’s put together my belt doesn’t ride up on secondary at all it’s flush
 

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Yes the movable and fixed got machining they didn’t do anything inside the primary, they said .75 mil of each sheave to make 1.5
Also I’ll add when everything’s put together my belt doesn’t ride up on secondary at all it’s flush
Did you check your belt width?? Typically when you add shims you belt is above the secondary on the 700's.
 
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They machined the wrong area of both sheaves and screwed up his system. I bet if he ever gets on the road with those parts it tops out at about 50 m.p.h. in high gear.
I'm glad we have COOP so we don't take a chance of using the knuckle head that messed up his bike.
 
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Discussion Starter · #33 ·
Did you check your belt width?? Typically when you add shims you belt is above the secondary on the 700's.
I haven’t added any shims yet just with machining it should ride up a little and it doesn’t , the belt is brand new ac delco belt
 

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Discussion Starter · #34 ·
If you haven't do your self a favor and service the secondary and install all one weight rollers like 18's or 20's
I’m putting in all 17 g weights , going to shim it to what I can get max , then deside between purple or gold spring ,
 

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I’m putting in all 17 g weights , going to shim it to what I can get max , then deside between purple or gold spring ,
17g weights are going to have you reving high, sick with 18 or 20gm weights. Also be in your best intrest to grab an oem belt, none of the aftermarket belts are anywhere near the same quality.
I know your into it for a pile of money now, but if it were me, i would bite the bullet and buy a new sheave and start from scratch since they messed yours up. It atleast contact coop and see if he might be able to salvage yours.

As for a spring, i would start with a purple.

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Discussion Starter · #36 ·
Hello everyone ,
I’ve got a few updates , today I put in shims 1.5 and switched to gold spring , running mix 19.8/17g average of 18.4 g really impressed with how this machines preforms now I even tried to go to 1.7 shim and that was a no go screws were touching the cage and belt was so low it was riding on the collar and rubbing the belt . I guess they must have machined something as 1.5 seems to be my max .. also did a ratio and at 1 rotation I’m 4 over,, as var as I can figure out that’s 2:85:1 I think could be wrong ..
 

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I was thinking 1.5mm shim was very close to max on a stock sheave, .7mm on Coops machined sheave, I think you might have very little taken off your sheave or even this shop may have through your balance off for the way your belt is suppose to travel in the sheave for the price they charged you, you could have stuck with your stock sheave adding 1.5 mm and made very close to the same gains. Coops only!!
 

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Yeah the shop screwed you. Hopefully nobody else pays them for their hackjob.
 

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1.5mm is pretty much the max on a 700. At 1.7mm you get belt rub on the cover. It really sounds like that sheave want machined down, more like cleaned up with a rard buff, or possibly ballanced as Griz7 said.


Where are you getting the numbers due your weights? What brand are they? Pretty sure they aren't oem, i don't recall yamaha having 17gr weights, i was pretty sure they only had 14, 16, 18, 20, 30. No odd numbers, and definitely no decimal point numbers.

Are they epi weights? Are you weighing them with or without the covers?

Why did you choose a gold spring? What are you running for tires on this bike?


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Discussion Starter · #40 ·
1.5mm is pretty much the max on a 700. At 1.7mm you get belt rub on the cover. It really sounds like that sheave want machined down, more like cleaned up with a rard buff, or possibly ballanced as Griz7 said.


Where are you getting the numbers due your weights? What brand are they? Pretty sure they aren't oem, i don't recall yamaha having 17gr weights, i was pretty sure they only had 14, 16, 18, 20, 30. No odd numbers, and definitely no decimal point numbers.

Are they epi weights? Are you weighing them with or without the covers?

Why did you choose a gold spring? What are you running for tires on this bike?


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The weights I’ve weighed them all oem part number
3b4-17632. 19.8447 with cover
5km -17632 -17.0097 with cover
5GH -17632 -14.1748 with cover

I understand someone back in the day someone said those same numbers came out at 700 was 18 g 20 with cover
660 was 16 and 18 with cover
450 was 12 and 14 with cover
But there actually not

as for tires there 28” zillas I know there really lite tires but I also run 27” silverbacks and 27 dirt commanders just depends on where I’m going the gold felt the best for my style of riding , I found the purple just didn’t have that low punch I was looking for maybe down the road I’ll switch the green spring witch is right in the middle gold punch with purple back shift
 
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