Comet 780 question

Phantom59

Been looking around the web for information on this clutch and stumbled on my old golf cart site. I have a Land Pride UTV with the 780 clutch and I am having a couple of issues with it.
First problem is sometimes after running full throttle the clutch will fail to disengage and kill the engine when I stop. The clutch is enclosed in a cover and looked very clean when I replaced the belt.
Second I was told by Land Pride that they had limited the top speed of the vehicle with the drive clutch. Is there some way they could keep it from fully compressing to lower the gear ratio?
This UTV has a 20hp Honda and 25 inch tires but will only run 20 mph. I talked to Dana who built the trans axle and they said it had standard gears and should be capable of higher speeds.

BGW

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csason

I know what a 780 looks like, don't know what your driven clutch looks like, which is where your basic *ratio* comes from, HOWEVER, the whole deal is RPM dependent..you can't go fast if your rpms don't spin the clutch.

You could have a 80 hp motor that won't spin past 3500 and that cart is only going as fast as that will take it.

If it is sticking, I just blow them out and sometimes spray wd 40 in it..and it stops sticking for a quick repair.

to really see what is happening, I will put mine on jack stands or lock it in neutral, or both, and rev the motor to top end and watch the belt and clutch to see how they are performing. You could have a worn out belt maybe that isn't riding the clutches properly.

Phantom59

The belt is new and the driven pulley is the torque sensitive type. I guess I am going to take the cover back off to access the belt and pulleys. I'm just trying to get as much information as I can before I do that because it is a lot of work and it leaves the truck unusable until it is reassembled.

sho305

You should see something like this, though these are mostly stock golf cart clutches and it engages at pretty low rpm.
https://www.youtube.com/watch?v=XksLJlvY6KA
The secondary only senses torque to shift down under big loads or full throttle, otherwise it shifts up at part throttle so you can go faster at low rpm. It you wind the preload high it will not as much and rpm will stay high, like many utv do all the time. The primary is tuned to shift at WOT top rpm (around 3500-4K in golf carts), the only time it shifts at lower rpm is when the secondary lets it do so due to low torque running.

To limit speed it would have to not close all the way, that means the primary (on the engine) would not run the belt up to the top. Because the clutch has parts in it that limit it, or it needs more rpm than the engine is governed at. What is the diameter of the 780? Smaller diameter is less speed most cart clutches are similar to the comet 94 in size.

You should check the gearing while you are at it, see how many times the clutch (secondary) turns for one rear tire revolution (preferably in posi meaning both tires turn). My cart is about 13:1 stock gears for example, there are gearing calculators all over the net. The CVT in a G9 does overdrive to about .9:1, together that is about 11:1 total at full shift (13 x .9 = 11). With a 22 tire and about 5K rpm I get 30 mph or so. So at 3600rpm on a governor it would be much slower, with a stock lawn engine.

Phantom59

I believe I can get some lube into the holes in the clutch cover through the cooling hole in the belt case. What would be the best thing to spray in there WD40 or lithium dry lube? May also be able to look in there and view the belt while I rev the engine.

fstg21

dry moly or graphite lube only. no oil or teflon. Spray is fine.

The Tracker has 12:1 of 13:1 gears.



This is the Land Pride driven clutch. 9.25" and 7" diameter for the 780

It is a good match.

Take a black marker and make a solid line on both sheaves of the drive clutch vertically.

Then go drive the UTV at full throttle for a few minutes.

Stop and see how much if not all of the marks are worn off.

If it is all somewhat worn then every thing is working, if not report back.

It could be the driven is sticking part way shut.

Also if you can use a tach or timing light to check you idle. It should be 1600rpm, the clutch is setup to engage at 1700rpm.

It is very easy to turn the idle down a bit if needed.

You should also lubricate all the throttle linkage and the engine and the pedal once a year.

Phantom59

Wow someone who even knows want a Treker is I'm impressed. Thanks for the information I will try to lube it and see what happens I really don't want to take the belt case back off. With that gearing it sounds like I'm going to have to do some major modification to get 30 mph out of it and will loose towing power in the process.

fstg21

You can bump the governor to 4500 and not change or damage anything.

Just a cheap tachometer and a spring.

That should get you close.

Phantom59

Thanks looks like I will have to take the case off to access the clutch so I will be able to check it all out. I got an email from Dana today with the part numbers for the 4:10 gears so I am trying to locate them.

Phantom59

Sorry thinking about big trucks 10 to 1 gears