Drive Clutch Tuning

[Dane]

This is mainly for all the 825 guys complaining about the engine rpm's when driving around at moderate to slow speeds. The drive clutch, the one attached to the engine is centrifually actuated. Of the two clutches in the Gator's drive system it's the only one that is controlled by rpm. The driven clutch is controlled by torque and belt tension.

The easiest way to change how the drive clutch operates is by changing the spring. The spring holds the clutch open and not engaging the belt. Weights inside the clutch get flung outward by centrifugal force. Part of these weights have a camming surface that pushes the clutch pulley side inward, forcing the belt to climb higher just like shifting to a higher gear. Springs are available in different lengths and with different diameter wires. Basically a heavier spring makes the clutch open more reliably at idle but also delays "upshifting". A lighter spring allows the clutch plates to close at a lower rpm basically shifting into a higher gear sooner.

I have this one off the engine but changing the spring is very simple and can be done on the engine. Getting to it is the worst part. You will probably need to remove the center bolt and it's thick, custom washer. Then remove the six bolts around the perimeter. When removing the last bolt get ready for the clutch face to pop out a couple inches.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch1_zps06acca35.jpg

Notice that the face plate has three arms. One is marked with an "X". Inside the clutch you will also see another "X". That's the important part. When re-assembling make sure you line up the X on top of the X. It's not fussy. You've got a 33.3% chance of getting it right just by guessing.

Lift off the top plate and underneath is the spring, sitting loose.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch2_zpsd1a92c14.jpg

Pull off the spring and you're left with the main clutch assembly.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch3_zps0d68721b.jpg

[Dane]

Now that you have the clutch apart you can see how it operates. In the center you can see one of the three weights that magically make the clutch work.

The weight in this photo is down and you can see the back, machined face that cams against the face plate causing it to squeeze the belt.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch4_zps2fb2746a.jpg

Here I'm holding it up which is how it will look when the engine is turning.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch5_zpsbe96172b.jpg

[Dane]

Depending on the spring you choose re-assembling the clutch will be easier or harder as you have to compress the spring. The tricky part is the plate has to remain relatively flat/parallel so it does not bind on the center shaft. Doable without special tools if you have two people. One to hold the clutch face plate against the spring while the other quickly gets a couple bolts started.

If working solo a simple trick is to use a couple pieces of threaded rod (1/4-20) about 6" long. Thread them into the clutch housing on opposite sides. You can't get them exactly opposite so you may need to wiggle the face plate to keep it moving in freely. Tighten the nuts alternatingly to keep the face plate mostly parallel as you go. If it starts to bind back off the nuts and wiggle until it's free. You don't have to compress the spring fully. Just get it close enough that the 6 bolts that attach the clutch face can reach. Once you get them started work in a pattern accross the face tightening each bolt a little like tightening tire lug nuts to keep the face moving in parallel and freely. If you feel it binding don't force it. It goes smoothly if the plate is square but if you get it crooked it will lock in place and you risk bending things if you force it.

http://i922.photobucket.com/albums/ad67/pilotdane2/2014/Gator%20Engine%20Swap/Drive%20Clutch/Clutch6_zps00805cb3.jpg

[Dane]

Since there have been complaints that the 825 rev's too high when driving around I wanted to point out that there is a trade off if you change the spring. A lighter spring will allow the clutch to slide into higher gear at lower rpm which will hurt towing and hill climbing ability. On the flip side it will shift into higher gear sooner so the engine isn't turning as fast when driving around at slower speeds. You really have to look at how you use your Gator and consider if it's worth the change.

The primary clutch will upshift solely based on engine rpm regardless of the load. Generally I don't think it's a good idea to change the clutch unless you live in flat country and use the Gator just for driving around. The 825 has a small displacement 3 cylinder engine. It's made to turn fast. Those tiny pistons have to move a lot to make it's full power. Changing the spring can get you lower RPM's when driving around at 10 mph but you will lose power. If you get bogged down in mud or want to haul a heavy load up a hill you will think your Gator has lost some power.

Once you get the engine up to an rpm where the primary clutch is fully closed there is no difference between a stock or lighter spring. Changing the spring will only affect what happens before the clutch gets fully closed (high gear). So, top speed will not change and the power you feel at faster speeds will not change. It's the take off, acceleration and towing that will suffer.

[GATORDONE]

Very good information Dane!! :Thmup:

[Bunky]

I would not even try the spring change. I will put on the silent rider next week. I will try to do a before and after with a video to see if it captures it.

[ESierra62]

This is good information, however this does not address the issue of downhill speeds. I have pretty much gotten used to having to drive with two feet to control downhill speeds. The problem of having to apply throttle to keep the engine rpm's up to keep the belt engaged is kind of ridiculous. What ever engineer came up with that little plan should be tossed. It is hard on the breaks but is doable! So my question is there a fix yet for this problem? I live in the mountains of Eastern California and weekly am going for drives in them. On steep down grades it can be a bit unnerving. It would be nice to have that little engine or the clutch be able to build compression to allow the 825 to come down without having to give it throttle and squeal the breaks all the way down! Any thoughts?

[Bunky]

After reading on one of these forums that running the 825i in high when driving at slow speeds, I started driving in L. It actually drives better to me at low speeds. When in L, you never need to worry about downhill speeds, it always seen to be engaged since the rpm is higher.

[Dane]

"Fix for the problem"... technically it's not a problem in that nothing is malfunctioning. The drive clutch is designed to let go when the engine speed drops below a certain rpm. You can say it's a feature you want but don't have.

Some manufacturers have a number of ways to provide engine braking. None come without a price. They may have one way bearings and run tighter belts which can lead to shorter lives for some components so there is a price to be paid for the feature. Honda and Kubota are the only UTV manufacturer I know of that is not using the CVT type drive and Kubota probably has the best engine braking available but it's a very different type of drive. In the end you just have to consider what features you want in a vehicle before purchasing.

[DIXIEDOG]

Couldn't someone put a 2013 or newer clutch/belt on their 825 and gain engine braking? :hdscrh:


I've personally never had a problem tapping the throttle to keep it engaged but if you ride down a steep enough hill I can imagine it could be a hassle.

[duling]

That's a good idea! Hopefully one of the techs will chime in.