kammak,

How much speed did you gain by using the 5/16 shim. Do you have the power spring also. Talonman said that the shims with a stock spring are equivilant to the powerspring, but with the power spring would be to much.

Don't clasify the spring in your mind as a top speed mod. It is a mod to help your buggy to get to top speed quicker. It may also help to keep the heat a tad lower in your CVT by reducing friction from slippage.

If you get even one more mph top speed out of the spring feel lucky. It was not it's purpose. It would just probably mean you had some slipping going on inside your CVT that you did not know about.

Too much extra pressure on the belt would be a bad thing too. The 1500rpm torque spring already takes a muel to compress in the clutch. I don't even think you could put a shim, and the spring in there togeather, and be able to catch enouigh teeth on the 1 1/2" nut to keep it closed.

A 1500rpm spring and a shim togeather would not have any big advantage, and would have potential to do harm.

My 2 cents.

Talonman,

Thanks! That makes sense.

Glad to help.

I have a Dune 150. I used a piece of 2" schedule 40 fire sprinkler pipe. The 5/16" thickness was too much. The clutch does not fully disengage now. The buggy is only one month old. I am wondering if the spring or clutch get weaker over time, and you need a bigger shim over time.

I'm not understanding the clutch not disengaging?Is it possible there is something not assemble correctly.The drive and driven pulley are constantly turningwhen the engine is running.The more you rev the engine, the pads on the secondary come out and engage to the outer bell and put it in motion.The shim only changes operating rpm throughout the power band and helps with belt squeeze to prevent slippage.
Ken

When the engine is at idle, the driver clutch pulley should not engage the sides of the belt. The belt should be loose in the pulley and resting on the bronze bushing around the hub. The bronze bushing serves to protect the belt from rubbing against the spinning hub at idle and also to support a portion of the movable sheave as the sheave moves toward the engine during engagement. from http://www.gokartsupply.com/trouble.htm

I think this explains that the proper setting would be one that just barely allows the belt to slip while at idle. That will make it easier to start and idle. I am starting to understand now that the spacer is increasing the preload on the pulley. With the spring load adjusted too tight, you can never get the engine to idle low enough to disengage the belt from the pulley. That is the problem that I have right now with the 5/16" spacer. I have to crank more to get it started then gas it and go before the engine stalls.

I wish you could start the engine while still rolling without having to push the brake.

I'm starting to think we are playing with 2 different systems.

I think that explanation from gokartsupply is just plain wrong. The belt should never be loose. If the belt didn't move then clutch wouldn't spin.

Check out this classic post:
http://www.buggynews.com/viewtopic.php? ... =cvt+video

Re-reading the gokartsupply page I see that what they are calling the "driver clutch pulley" is the variator. By stating that the belt should not be contacting the sides of the pulley I think they mean it should be resting on the sleeve at the bottom and not be squeezed by the sheaves. Once the rollers move the sheaves will squeeze the belt & move it higher on the diameter. The variator/fan/sleeve are always spinning with the engine so the belt will always be moving unless it's REALLY loose.