Need to raise shift rpm about 2k rpm.

[Vbzatty]

To start off, I’m not working on a sled but a Yamaha golf cart with a RZR 800 motor. But this forum, by far, is the most knowledgeable about cvt tuning. Here’s my issue:

The cart is using the stock Polaris P85 primary with an EPI red spring and the stock Yamaha secondary. Ideally shift rpm would be 5800-6000. Right now it’s only 4000rpm. From 4000 rpm to 6200 I’m in over-rev and mph and revs climb until I hit 53mph and the rev limiter. The acceleration is lacking as its upshifting way too soon. I essentially have only one speed; shiftout is happening way too soon.

Idle is 1200rpm and engagement rpm is 1500. That seems low but it makes for comfortable driving around town.

I need to get my shift rpm up about 2k rpm which I know is a lot. There are three ways I can do this; a primary spring with a higher end rate, lighter weights, or a stiffer secondary. Most people recommend changing rpm with weights but can I change rpms that much with weights or should I start with the primary spring? Or should I stiffen up the secondary and pull up rpms by making the primary work harder. Everything I’ve read says the latter is a no-no.

I’ve spent hours on this forum and have learned so much and look forward to any help you guys can offer me.

Colby

 

[eddy]

Try a primary spring with the same starting rate and about 100 lbs more finish rate and report back.

 

[slash]

what weight weights are you using ??

 

[volcano buster]

What engine did the cart have originally?

Torque curves may be considerably different as well as operating rpm's such that the secondary setup is not matching with your existing power plant.

 

[kanedog]

You May need higher gearing in the cart.

 

[kanedog]

You May need higher gearing in the cart.

I take back this suggestion. I think the clutches are worn out.

 

[Dynamo^Joe]

Polaris P85 primary
EPI red spring
Yamaha secondary
Ideally shift rpm would be 5800-6000
full throttle is 4000rpm

Flyweight determines engine speed at full throttle
IF need more engine speed, THEN reduce flyweight
1 gram = estimated 200 rpms.
6000 rpms [needed] - 4000 rpms [actual] = 2000 rpms
that's like 10 grams you in theory would have to reduce.

Dont know what secondary spring you have, whether it a torsion [probably is] or compression spring, but if you know the forces of the secondary spring, then can calculate a new stronger one.
Or
If know the helix angles, then can calculate a new helix and run that to help overcome the low engine speed.

other than that, look at the gram amount of the flyweight and see if there is one that's 7~8 grams lighter and that will get you pretty close.