How about pulling the driven clutch to install a shorter belt?

woodyking

Anyone do this? I'm running the shortest belt I can get on, but after it's on there is quite a bit of slack. I believe it would be geared lower, making contact deeper in the drive clutch, if I had about a one inch shorter belt. But, I'd have to install it at the same time as one of the clutches, like have the belt on the clutch before putting the clutch on the shaft. How about it? Thanks in advance for info. Woody

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pizzamaker

i have done that a few times and it worked good, but it may make it a bit jumpy when you start off!

woodyking

Thanks! Which clutch did you pull? I'm kinda torn between them..... Woody

pizzamaker

i pull the drive clutch, its a lot easier to put back on.

woodyking

Thanks, I just found and printed a belt list off ebay of all the sizes with measurements made by Dayco so now I'll have to try a couple going down from what I'm running now. Lots of in between sizes to play with! Thanks again, Woody

scottyb

I am not sure you are going the right way .... I understand that the rear driven clutch acts like a variable speed gear ... the further out on the circle the belt is the lower the rear end gearing and when it is flying down the road it is opening to let the belt go down the ramp to a smaller ( taller) gear. At the same time the drive clutch is doing just the oposite.....so by putting a real short belt on it you loose low gear...unless you are just looking for top end only? What do you guys think?

I am running the recommended shorter 2 stroke belt on my 4 stroke workhorse. With 20x11x10 tires it gps at 26.3 mph andf has already lost some low end which I plan to gain back with some custom clutch work from Dixie ( see sponsors now!)

ruredy

What cart do you have? what belt are you running?
The problem with going to short is your cvt will stay engaged all the time and it will probably mess up the driven clutch and trash the rears input shaft bearings.
The stock belt rides about halfway up the sheaves on the drive clutch when first engaged. The whole idea behind the shorter belt is for the belt to engage closer to the shaft on the drive clutch and for the belt to remain in its original position on the driven. This is how you see a change of the gearing ratio.
Stringing the belt so tight it's pulls into the driven clutch will only mess up your clutches and rear end not to mention sending you on a backward path as far as the gear ratio is concerned.
Also... while you may be able to change the belt by removing/replacing the drive clutch, I doubt you can do this with only removing the driven because the shaft sticks out way to far. I've changed a bunch of belts and have never needed to remove a clutch to do so.

woodyking

I would never want it short to the point where it kept any load at all on it, just trying to find where it would be happy/loose with minimum slack. It would still have to have enough slack so as not to be gripped at all until the drive clutch moves in some. NEVER tight, just less slack. As you noted, the engagement doesn't start until the drive clutch is closed enough for the belt to be about midway. This is not using any of the lower potential that is lower on the drive pulley, right? The belt would not need to put any force on the shafts or bearings at all, only when the drive pulley moves in and grips it. I'm shooting for a lower ratio mainly, but also see it being better on the high side as well, since the shorter belt would not only start lower, but end up with a higher ratio as it would pull deeper into the driven clutch once the drive clutch was fully in. So it would be starting lower in the drive, ending up lower in the driven at full rpm. If it's designed equal, the cross section of the pulleys' pattern should not change the bearing loading regardless of which area of the pattern it is in at any particular moment. Now, on the other hand, if the driven pulley can't accept the amount of depth equal to the drive pulleys' take-up, then it would load the bearings to the point of the amount of force the centrifical clutchs' closing mechanism puts on it. Maybe this is what you're thinking? Seems like any well designed drive would have equal travel on their pulleys, and the drive clutch should max out before the driven one runs out of travel. If you had a driven clutch out where its' maximum opening and depth that the belt could go could be measured, that would tell you. I've replaced wear buttons in them but at that time wasn't considering stuff like this. Anyone got a driven clutch laying around? I'm betting their engineers have it equal take-up, but there's no real way to know without measurements.
Could be done also like this, raise rear wheels, go shorter on the belt until when the drive pulley is fully in, the belt is almost at bottom on the driven pulley. Then, if you have some slack back at idle, you would have your best possible belt and ratios.
It's a 90 model 2 cycle that I'm playing with. It has larger tires and still has more low end power than stock 295 four stroke engined carts, but I'm looking for a little more if it can be had. Seems like this would be a "free" win-win.
Didn't mean to write a book, but doesn't that make sense? Unless the driven pulley can't eat up the amount of belt the drive pulley takes in, then it should work, and with no loading on anything that isn't already there in normal operation. I appreciate you thoughts and experience, since I'm just theorizing without having actually done any testing yet. It all started when I noticed how much slack it had stock, was an old belt anyway, so I got a new one which is 1/4" shorter. Of course, this isn't much, and it still has lots of slack, so the next belt size down is another 1/4", etc. Thanks again, I really appreciate all the help and thoughts I can get. Woody

ruredy

opening/closing of the clutches doesn't have to be equal. The driven clutch controls the rate of the cvt's progression through its gearing. The drive clutch is forced closed by centrifuge forces from the engines rotation and can only close as belt length grows from the opening of the driven.
Anyway.. I always found about an inch shorter works great on the 4 stroke cvt, any shorter and you start loosing top end because the drive won't fully close. Don't know about 2 strokes, I have heard people using a yamaha belt on carts like yours (it's over an inch shorter) but I have never tried it. sounds like you have a good grasp on what you want/need.

woodyking

I pictured the drive clutchs' centrifical action squeezing the belt, and the more it tightened, the more the driven clutch had to give up. The driven clutch doesn't have any centrifical going on, but has to resist the drive clutch trying to close in more. The resistance can be more or less depending on the ramp angle and spring tension, more would make the gearing stay lower longer, less would make the gearing higher sooner. The end ratios would be fixed by the diameters and stay the same as long as you could make use of the full travel of both clutches. That's what I'm hoping for, to make use of as much of both their travel as possible.
Thanks for the info on the long driven shaft too, that would make it not work for changing shorter belts as you said. I'll try to take some pictures if I get into it and post them. Sadly it won't be today or anyday real soon, but definately before long........ That's southern talk for when I get a round to it.
If anyone knows how deep the belt can go into the driven pulley, like, can it go all the way down to the shaft or not, let me know. Thanks! Woody