Noob clutch question

D

Drwe

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Joined
Nov 28, 2021
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I got my 98 vmax 700 xtc out on a 200km rip this week. I noticed it was very fast from a dig or 20-40mph when smashing the throttle, it would rev up to 8300-8600, but usually around 8500 depending on what I assume was the traction situation at the time (I'm not studded).

However, it would quickly come down and hold at 8000 rpm after some speed maybe 60-80mph, or in that range and have less power. Smashing the throttle from that 60-80mph speed only sends it up to around 8000 rpm, give or take.

I'm still learning about how these cvt drives work, I know I have a red (doubtful it would be pink) spring in the secondary set to 60degrees. As far as I know the stock spring would have been green which would have provided more backshift, I could change the secondary to 70 degrees and experiment.

As an aside, I'm getting about 45L/100km on the trails, I'm not sure if that is typical. I'm not sure how changing backshift would change fuel consumption.
 

Maybe try your setting at 90 twist, see if that takes care of it if you dont have a green spring to try.
Do you still have the 45 degree helix?
 
If its a 45, there would be a 5 in the part number thats stamped on the outside of the helix.
Try it at 90 and see how it reacts.
 
MURDER YAMAHA said:
If its a 45, there would be a 5 in the part number thats stamped on the outside of the helix.
Try it at 90 and see how it reacts.
Click to expand...
picture from before I cleaned and rebuilt the clutch this year, but I see "50" on it. I will try 90 deg as you suggest.
 

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All those 700 red heads in those years were known for over-revving in the lower speed range, and then under revving at higher speeds.
The best fix is a clutch kit, however if you you find a helix that the RX-1 and Apex used, it is a 51-43 and would solve a lot of your shift issues.
You want that thing to stay at 85-8700 for best speed.
You may have to lighten the weights also if you use a 51-43
Also, about your fuel mileage, if you can still get a set of new needle jets from Yamaha, change them out.
 
74Nitro said:
All those 700 red heads in those years were known for over-revving in the lower speed range, and then under revving at higher speeds.
The best fix is a clutch kit, however if you you find a helix that the RX-1 and Apex used, it is a 51-43 and would solve a lot of your shift issues.
You want that thing to stay at 85-8700 for best speed.
You may have to lighten the weights also if you use a 51-43
Also, about your fuel mileage, if you can still get a set of new needle jets from Yamaha, change them out.
Click to expand...
Thank you. Do you have the part# for the oem 51-43 helix? My brother has an 06 apex I could steal it off of for testing. The feeling of 8500+rpm vs 8000 is hugely different. Where are people buying clutch kits from these days?
 
Also, while I believe I understand that rpm tuning should be done with primary weights first, the over/under revving nature of my sled seems best addressed by these secondary changes.
 
ok.
on another 700SX that I had, it would run 9000rpm bone stock with the 8DN belt.
But it was consistent, would not drop down later in RPM. We ended up using the heaviest rivets in each hole with stock weights, and changed the rollers to get it to run at 8600 rpm.
 
Drwe said:
Thank you. Do you have the part# for the oem 51-43 helix? My brother has an 06 apex I could steal it off of for testing. The feeling of 8500+rpm vs 8000 is hugely different. Where are people buying clutch kits from these days?
Click to expand...
It says 8FA on it.
If your primary has the 8CH weights in it, I found it was impossible to get a straight shift out of them.
By straight shift I mean that when you pin it, the revs climb to 8500 and stay there all the way to 100mph.
I'm not sure who offers clutch kits for these older machines now. You could try Hauck or Ulmer
 
You should also check clutch alignment and center to center.
I know for a fact after years and years of experience that if the center to center is greater than spec, that the revs will fall the faster you go.
 
If given the choice to swap some oem 8DF or other weights into the primary vs changing to an apex 51/46 helix, what is preferable? I'll also look for a clutch kit
 
take a lilttle weight outta the tip of the flyweights and put 14.5 mm rollers in if they not ! you'll be close then
 
Last edited:
im sorry i got it backwards ,I miss read your post, you should put in a bigger roller to increase your shift out rpm. try a 15 mm roller if its not or perhaps a 15.6
 
Im no expert, but
You are getting the correct rpm on the initial hit.
I would focus on the secondary to fix your issue first.
 
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