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Discussion Starter #1 (Edited)
Well it looks like for the most part that our rainy spring is about to end so its time to get ready for some clutch tuning. I bought one of those little tachometers for testing purpose only and put it to use after I mounted it. My bike is a 2017 708cc Grizzly all stock (Except EHS Fuel Controller) including the tires & belt. It has 40.4 hours on it and 540 miles. The tire PSI was set at 7PSI and the air temp was between 55*- 60*. This is a average of 2 to 3 test for Rpm's on a dry paved road. FYI, Once warm the idle settles in right at 1600 - 1610 Rpm's.

10 MPH = 3250 - 3280 Rpm's
15 MPH = 3760 - 3800 Rpm's
20 MPH = 4150 - 4180 Rpm's
25 MPH = 4410 - 4440 Rpm's
30 MPH = 4730 - 4750 Rpm's
35 MPH = 5050 - 5080 Rpm's
40 MPH = 5380 - 5410 Rpm's
45 MPH = 5650 - 5680 Rpm's
50 MPH = 6010 - 6040 Rpm's
55 MPH = 6240 - 6280 Rpm's

That is all I had time for tonight but will try to get the 60 & 65MPH - Rpm's before the rain moves back in tomorrow for a day or so. In the Pic. When I first started the Griz the tach was set on the wrong setting so it only read 1/2 the Rpm's it was supposed to.
 

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Cool! Thanks for posting it
 

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@Zrt1200 thanks great info.

Please tell us what brand and size tires you are running and maybe an estimate of the total weight you are hauling.
 

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was your speed using the ATV's speedometer, or were you using a GPS?
 

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....because, if your tires are larger than factory, the speedometer will read lower than true, due to more travel per tire rotation. And the inverse is true for smaller than factory tires.
 

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Discussion Starter #6
@Zrt1200 thanks great info.

Please tell us what brand and size tires you are running and maybe an estimate of the total weight you are hauling.

I am running the factory stock Maxxis Muo6y tires. 26X8X12 & 26X10X12. The tire circumference 80.625/ pie (3.14^%) = 25.664" diameter. I did a internet search with no luck on the tire weight. I would assume they are a pretty lite tire though.


was your speed using the ATV's speedometer, or were you using a GPS?
Yesterday and earlier today I was using the stock speedo. I then put on my GPS performance meter. See the next post as soon as I get it wrote up as it will have a Lot of info including ET times and MPH's for giving distances.


....because, if your tires are larger than factory, the speedometer will read lower than true, due to more travel per tire rotation. And the inverse is true for smaller than factory tires.
To my surprise the stock speedo with the stock tires are with in 2-3MPH of the GPS.
 

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Discussion Starter #7 (Edited)
Day 2 of collecting info before I start clutch tuning which will be a little bit as I have to go out of state for a few days. As promised here is the Rpm's for 60MPH = 6600 Rpm's and 65MPH = 6800 Rpm's. I also checked the lower MPH VS Rpm's again today and they were the same. I then put on my Turbo Dynamics GPS Performance meter which shows GPS MPH and Elapsed times from a standing start. The reason I have this meter is for testing and tuning of our Prostock grass drag snowmobile. I have tested the GPS performance meter against professional wired timers and it is very accurate and very consistent. It should be though for $350 bucks. So here is the data collected today.


GPS MPH --------- Stock Speedometer MPH
10 MPH ---------------- 12 MPH
15 MPH ---------------- 17 MPH
20 MPH ---------------- 22 MPH
25 MPH ---------------- 27 MPH
30 MPH ---------------- 32 MPH
35 MPH ---------------- 37 MPH
40 MPH ---------------- 42 MPH
45 MPH ---------------- 48 MPH
50 MPH ---------------- 53 MPH
55 MPH ---------------- 58 MPH
60 MPH ---------------- 63 MPH
64 MPH ---------------- 67 MPH
Top Speed on the GPS was 64.2 MPH vs 67 MPH on the stock Speedo.
Now here is some interesting info for clutch tuning and is the reason why I bought this GPS....


0-60ft 6.20 Seconds at 28.8 MPH
0-300ft 10.61 Sec @ 49.7 MPH
0-500ft 12.81 Sec @ 55.1 MPH
0-660ft 14.76 Sec @ 57.4 MPH (1/8 Mile)
0-1000ft 18.65 Sec @ 61.3 MPH
0-1320ft 22.16 Sec @ 62.2 MPH (1/4 Mile)
0 to 60MPH 17.1 Sec and 862ft
Top Speed 64.2 MPH


Edit. I was just thinking about the 60ft times. If I moved even a 1/2 of inch before I hit the throttle the ET would be off as this performance meter starts at the first sign of movement. When I get back I will take a second run and see if the ET's match up or not. If Not I will post the correct ET's. Either way I will let you all know.
 

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Discussion Starter #8
As you can see in Post #7 there is a lot of room for improvement in the 0-60ft ET and IMO there is room for improvement from 500ft to 1000ft. I did notice from a dead stop when going WOT the Rpm's stayed lower (Around 3500-4200Rpms) for about 3 seconds. I will see if I can borrow my boys GoPro and get a video of the Rpm's from a standing stop start when I get back. FYI, I am not into top end speed but I do like quick acceleration.



Speaking of quick acceleration. Our ProStock Drag snowmobile which is a 1000cc 3 cylinder 2 stroke that pumps out 290HP at 9400Rpm's will do a 1.1 Sec 60ft and cover 500ft on the grass in 4.3 sec @ 117MPH. Now I do no the Grizzly is not even in the same category as that sled is in but that sled is why I own the GPS performance meter and it has helped us dramatically in clutch tuning.
 

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Discussion Starter #9 (Edited)
Update. As I suspected. I must have moved a 1/2" to 1" before to trip the timer so the set of ET's (Elapsed Times) in post #7 are no good. I did a few runs today and the ET's are Much Faster. The MPH is still close but the ET's are Way better.

Run #1
0-60ft ---------- 2.14 Sec @ 30.2 MPH
0-300ft ------- 6.53 Sec @ 50.0 MPH
0-500ft ------- 8.75 Sec @ 53.7 MPH
0-660ft -------- 10.73 Sec @ 56.9 MPH (1/8 Mile)
0-1000ft -------14.76 Sec @ 57.6 MPH
0-1320ft -------18.33 Sec @ 60.2 MPH (1/4 Mile)

Run #2
0-60ft --------- 2.11 Sec @ 29.9 MPH
0-300ft ------- 6.49 Sec @ 49.8 MPH
0-500ft ------- 8.70 Sec @ 54.7 MPH
0-660ft -------10.65 Sec @ 57.3 MPH (1/8 Mile)
0-1000ft ----- 14.57 Sec @ 60.0 MPH
0-1320ft ----- 18.13 Sec @ 61.5 MPH (1/4 Mile)
Top Speed 63.1 MPH (Note. I did not hold it WOT as long to get a full top end run today but its still with in 1.1 MPH so close enough.)
0 to 60MPH time and distance. 13.05 Sec and 865ft.


Note. In Run #2. I held the rear brake and brought the RPM's up just high enough to feel the centrifugal clutch engage (Power Braking) to see if that would help the ET's a lot. It did help by .020 to .030 Seconds. That's not enough gain to wear out the centrifugal clutch IMO and I wont be doing it again.
 

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All awesome information! Can't wait to see the data after more tuning.
 

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Discussion Starter #11 (Edited)
Now that I have a factory stock performance baseline I am read to start clutch tuning. So I pulled some plastic off and pulled the clutch cover off and the first thing I noticed is the belt is already to the top of the secondary sheave (Actually about 1/64th above) and the belt is just touching the cover. So I checked the clutch ratio and its 2.42 to 1 so no clutch mods have been done. Next I checked the belt width and its 1.251" or 31.79mm wide. So I checked the length. My belt is 37-5/16" long or 37.312". I am assuming my stock Yamaha 3B4-17641-00 belt is long??? Does anyone know what the stock belt length is supposed to be?? I cant hardly do any clutch mods with the belt already hitting the cover as the belt rubbing will only get worse??
 

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I have the length somewhere. I'll need to look.

Proper way to measure belt is-
Draw a line on the edge of the belt.
Find board about 4-5 ft long.
Hold the outer cogs tight on the board with the line down. Make a line on the board adjacent to the line on the belt.
Roll the belt along the board until the line on the belt contacts the board again. Mark the board at this point. Now measure between the two lines on the board.
This is the true length of the belt.

Sent from my SM-S327VL using Tapatalk
 

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Discussion Starter #13
I have the length somewhere. I'll need to look.

Proper way to measure belt is-
Draw a line on the edge of the belt.
Find board about 4-5 ft long.
Hold the outer cogs tight on the board with the line down. Make a line on the board adjacent to the line on the belt.
Roll the belt along the board until the line on the belt contacts the board again. Mark the board at this point. Now measure between the two lines on the board.
This is the true length of the belt.

Sent from my SM-S327VL using Tapatalk

You are talking about checking the pitch length. I can do that as I have done that before. Thanks.
 

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Discussion Starter #14
After talking to Griz7 to see if he had problems with his 16 Grizzly and a Coop45 sheave as well as Ridgway81432 about the belts hitting the cover. I did some more investigating. There is at least a 1/4" of clearance around the belt cover and the problem must be the stock secondary spring is not stiff enough when back shifting letting the belt balloon out touching the cover on deceleration. I took measurements in multiple locations and the one place its hitting there is 3/4" clearance when the belt is to the top of the primary sheave and 1" at the bottom of the primary sheave. So now that I know whats going on its time to continue with some clutch tuning.
 

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After talking to Griz7 to see if he had problems with his 16 Grizzly and a Coop45 sheave as well as Ridgway81432 about the belts hitting the cover. I did some more investigating. There is at least a 1/4" of clearance around the belt cover and the problem must be the stock secondary spring is not stiff enough when back shifting letting the belt balloon out touching the cover on deceleration. I took measurements in multiple locations and the one place its hitting there is 3/4" clearance when the belt is to the top of the primary sheave and 1" at the bottom of the primary sheave. So now that I know whats going on its time to continue with some clutch tuning.
This is the rubbing I had with my Coop machined sheave with a 0.5 shim and a worn belt. Never gave me problems. I've since replaced the belt. In this case my initial ratio was down to an awesome 3.175 / 1!

Though I'll admit, I find it odd you have rubbing with the stock set up
 

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Discussion Starter #16
This is the rubbing I had with my Coop machined sheave with a 0.5 shim and a worn belt. Never gave me problems. I've since replaced the belt. In this case my initial ratio was down to an awesome 3.175 / 1!

Though I'll admit, I find it odd you have rubbing with the stock set up

Ya I have to agree. The only thing it can be is the secondary spring is sacked out or Yamaha had a bad batch of them. I'm not worried about it at this point as that will be my second clutch mod.
 

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Discussion Starter #17
So my first clutch Mod is a set of wet slugs. Being I have the tools and equipment at home I went ahead and bought a foot of yellow brass for $6. at my local steel supplier (He wanted $7. for 6" Go figure??) and made up my own wet slugs. I knew I was going to do this so I had already bought the new gasket, nut, oil & filter to do this job. After I got it tore apart I made up the wet slugs. Each slug weighs 6.0 grams. Instead of doing a taper like the aftermarket does I did a .010" under cut so I no which side press's into the wet clutch. After dinner I will see if I can get it all back together.


I also called three semi local dealers in my area and none of them have a new Grizzly belt or new what the length was supposed to be. The next time I go up to my buddies place I will stop at a couple bigger Yamaha dealers on the way to his place and see if they have any belts in stock.
 

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Ya I have to agree. The only thing it can be is the secondary spring is sacked out or Yamaha had a bad batch of them. I'm not worried about it at this point as that will be my second clutch mod.
I seriously doubt your secondary spring is weak or bad. If that was the case your CVT would always overshift, your motor would be bogged out of it's power band and your performance data would immediately reflect this.
 

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Here are the 700/550 OEM belt specs. OD 37.125" PL 913.4 mm OD 943 mm




Your belt rubbing issue...With a stock CVT and everything working as it should. The forces of the engine braking will not slack up the belt enough to rub the cover. Some claim this happens when the rev the shet out of the machine in neutral (no load) and they see the belt flutter. With a load on the it will not happen.

What could cause enough slack to cause the rubbing is the secondary sticking.
Did you rotate the cvt 4-5 times to bring the belt all up before you read the 1/64" measurement?

Consider servicing the secondary. Cleaned it, check the movement of the button and re-grease it. I use high temperature waterproof wheel bearing grease.
 

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Discussion Starter #20
Here are the 700/550 OEM belt specs. OD 37.125" PL 913.4 mm OD 943 mm




Your belt rubbing issue...With a stock CVT and everything working as it should. The forces of the engine braking will not slack up the belt enough to rub the cover. Some claim this happens when the rev the shet out of the machine in neutral (no load) and they see the belt flutter. With a load on the it will not happen.

What could cause enough slack to cause the rubbing is the secondary sticking.
Did you rotate the cvt 4-5 times to bring the belt all up before you read the 1/64" measurement?

Consider servicing the secondary. Cleaned it, check the movement of the button and re-grease it. I use high temperature waterproof wheel bearing grease.

No I did not when I checked the measurement, But yesterday before I tore the wet clutch apart I was running the engine to warm the oil up. I did notice some times the belt would not stop at the top of the sheave while other times it would. You may have hit the head on the nail with the secondary sticking. I will tear it apart and see what I find. Thank you for the Measurements. FYI. My belt OD is 37-5/16"/ 947.7mm and my Pitch Length is 36-1/64"/ 914.78mm. So I do have a long belt to start with. I would bet if everyone starts checking the length of a new belt you will find they very a fair amount. In the Snowmobile world belts varies up to a 1/2" in lengths. When I do buy a new belt I always check the OD of them because they very so much.
 
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