conquest clutch rebuild parts

[Rock Doctor]

Ok, just so you all know how geeky I am...

I played with excel and I was right the first time.

Changing the spring rate translates the clutch force curve. The slope remains the same.

Changing the weight changes the slope of the clutch force curve. Proportional to the square of RPM.

F = (0.000341Wrn^2)-S

F - clutch force in foot pounds
W - mass of weights in pounds
r - radius of mass of clutch weights
n^2 - rpm squared
S - spring "weight" in pounds

I ignored that r changes a bit as the clutch operates and that S should really be a rate proportional to the "stretch" of the spring.

Less weight decreases the slope of the curve so if the clutch needs a certain force to come on line it will happen at a higher RPM. It also decreases the rate that the gears will change per RPM change.

LOL, OK, you completely lost me here
English Please

[JohnF]

English Please

Did I say that? LOL

Ok, You and Roger made different changes that affect when the clutch comes on line.

Let's say the clutch needs lbs of force to come on line and stock this will happen at 10 RPM. In fact, let's say the clutch force curve stock is 1:1 so at 0RPM there is 0lb clutch force, 1RPM=1lb, and 50RPM=50lb etc.

Your change adds spring force, which is opposite the centrifugal force. Let's say you change the curve by adding 3lbs of spring so at 0 RPM there is -3lbs of clutch force; basically, you moved the 10lbs to 13RPM but the slope remained the same so: 14RPM=11lbs, 15RPM=12lbs, ...

Roger's change flattened the slope. His still has 0lbs at 0RPM but the slope of his clutch force curve is 1.3:1. Both move the 10lb point to 13RPM. For Roger though 1RPM change add only .77lbs force.

The clutch force affects the gearing so changing the rate of clutch force changes the rate of gearing change.

[JohnF]

My dealer tells me that the weights aren't available any longer. I was thinking that I could pour some lead back into the drilled hole. I fear that pouring melted lead into a lead container is asking for trouble.

What do you guys think?

Maybe build some sort of sleeve that wraps the weight to pour into?

John

[Roger S]

What drilled hole are you talking about.. I missed something. 225 is what mine came with factory.. dunno what those higher #'s we saw on paper are about.

[JohnF]

What drilled hole are you talking about.. I missed something. 225 is what mine came with factory.. dunno what those higher #'s we saw on paper are about.

From the factory the weights for my conquest were 266g. There is a significant portion of each weight drilled from the top to make them about 225. It was done with a large drill bit to get close and then a smaller bit here and there to get it right. The larger bit hole is right down the center so that each weight looks like a thin walled cup. This is in the smaller diameter portion of the weight.

I'm not at home right now or I could post a picture.

[JohnF]

I had to put this here because it is very related to a part of this discussion.

From this post, jerseybigfoot gave us this link to an article on clutch tuning.

[Roger S]

Ahh, now we're (me) getting somewhere. No wonder conquests are so low rpm operating, with heavier weights. Well, now I know what to do for them. Use 225 weights and maybe some shim.

[JohnF]

Ahh, now we're (me) getting somewhere. No wonder conquests are so low rpm operating, with heavier weights. Well, now I know what to do for them. Use 225 weights and maybe some shim.

LOL, I don't think it's that easy. My 225g weights have me operating in a very narrow band that bumps pretty quickly against the governor.

The FD620D produces max torque at 2200 RPM and max HP at 3600 RPM.

When I watch RDs vids I know that I cannot putt around like he does. Say in the cabin moving vid where he sets up in the trees. I have to run quite higher RPMs just to be engaged.

Edit - your Briggs max torque at 2400 (Could be higher with your mods)

[JohnF]

Okay, I'm confident enough to stick my neck out here.

A couple of things first:

- I am a scientist. As a scientist I am not afraid to be wrong. If this is post is crap, say so, we can all learn; or at least I can.

- I've spent some more time reading and getting to know these CVT clutches. Some of that was hunting around here on 6x6World looking for what others have said about clutch tuning. Roger, dude, that 2400 figure is for the stock engine (Yeah, you know...) and I have no idea where your torque curve is. Some of you guys are nuts - and I mean that in a good way.

- RD asked "english please" and I don't feel I met that challenge. In fact, I had to find the english for myself.

My goal is a practical explaination of clutch tuning for the regular not-a-racer-yet crowd. The people that read this kind of post and first wave it off as fringe hobbiest mumbo-jumbo but yet in the back if their mind, wonder...

We will limit ourselves to only three variables: the driver clutch weights, the driver clutch spring, and the driven clutch spring. Things that are important are: max torque RPM, max power RPM, driven clutch cam, basic vehicle load profile, and belt.

Change anything I held constant and you need to start over.

The driver clutch spring and the weights affect the driver clutch force. (I am not describing specific forces for simplicities sake) The driver clutch (sometimes called primary) starts with a low force that increases with RPM. The driver clutch is RPM sensitive.

The driven clutch is torque sensitive, the higher the torque across it, the higher the force. This force opposes the force of the driver clutch and the belt balances where the two clutch forces match.

in our tuning here I will assume we are tuning for "the best". What does that mean? Different things... For this discussion I want a launch that does not hammer the machine or slip the belt/tires too much at a reasonably utilitarian load in the environment I will operate in (tough order), engine braking at low RPM for hilly operations, use of engines max power.

I am not modifying the stock engine so I will use the stock numbers of max torque at 2200 and max power at 3600. (Side note, Kawasaki lists these numbers and then has a derated suggested max power curve - WTF - not that confident in the engine?) I'm pretty sure looking at the power curve that this engine can produce more power at higher RPM but the manufacturer limits RPM with a governor. I will not remove it because I do not want to perform the modifications necessary to prevent the sudden scattering of engine parts due to overreving.

Ok, down and dirty. We have three things to adjust and every time we change one we will in some way affect the others. Changing the weights has the most drastic effect. In fact, we will consider the effect of driver spring changes (we are limiting ourselves to minor changes) as completely unimportant once the clutches engage.

Real quick description of the operation of our perfectly tuned clutches: We are sitting still at the end of an endless straight track. The engine is idling and the driven clutch is not spinning. We crank to wide open throttle (WOT). We feel the engine RPM start to rise and the clutch engages smoothly with no jerking or belt/tire slipping*. Engaging the clutch does not lug the engine in a way that makes us worry that it is going to die. As soon as everything is moving the engine RPM instantaneously locks on to max power RPM and stays there as we accelerate until the CVT fully shifts up and we sail along at max speed**. When we do come across a rise in the road, the RPM does not vary but we can tell that the CVT, due to load, is shifting down.

* There is - there has to be - but it isn't violent.
** assumes a governor at max power RPM. If none, then fully shifted and RPM again rises.

Now to do the tuning. You need a tachometer. Get your max power RPM memorized. Disable the governor for the moment because we can't tune the clutch with it in the way. Do the run like above and watch the RPM and time the run. If the engine overshot the target RPM then you need heavier weights. If it didn't get to target RPM then you need lighter weights. If it's pretty close let's not fixate because we may be able to make minor changes with the springs. Our goal is WOT = max power RPM. Put your governor back.

Next we adjust the driver clutch spring for engagement RPM. This is going to be the toughest choice you make because the torque needed to get the vehicle moving depends on your current conditions and load. If you want to pull houses at high altitude in 125 degree weather then engage at max torque RPM. If that can't do it then your vehicle probably can't do it. Probably you will want to be lower than that and you definately want to start at an RPM less than max torque (remember the smooooth requirement.) If when the clutch engages the engine dies then you need a heavier spring. If things hammer or belt/tires slip excessively then you need a lighter spring.

Last is the driven clutch spring. This affects how sensitive to load the CVT is and is basically the hardwired guy that picks which gear you are in. This one is a little tricky to measure but we can do a decent job with our tachometer and stopwatch. Do a run as above and if you gain acceleration you are headed in the right direction - lose acceleration, wrong direction.

Remember, each of these variables affect the other so cycle through these a bit to dial it in.

Changing elevation should not require weight change as max power RPM should remain the same (or very close, and yes, max power changes a lot). But, changing elevation will require redialing the engagment RPM because the torque needed to get things moving does not change but torque at RPM does change. Basically, higher elevation will require moving towards max torque RPM - a higher spring weight. Unfortunately, this spring is buried in the clutch and isn't easy to adjust so if you expect high altitude conditions then you may want to accept some slipping/banging at lower elevations.

There you go, my layman's understanding. (keep in mind, I've never done this before)

John

[Roger S]

If you want weights, google Gene Lintz (argo dealer) in Iowa for a phone #, he had weights and shoes last year.

Some guys here know a lot about cvt theory, but usually work on other hardware besides argos. I think you know enough about the situation to just try something and let us know how it turns out.

[berky84]

Great thread! I'm servicing/tuning my clutches this week on my new-to-me conquest. What was the final tune on your clutches John?

[Rock Doctor]

Great thread! I'm servicing/tuning my clutches this week on my new-to-me conquest. What was the final tune on your clutches John?

I love reading John's posts, but just to keep things simple, I would recommend trying this out:
Primarty Clutch: Put in a new spring. Test it out. Put a 1/8"-5/32" shim under the Primary Spring, test it out. (The thick shim will slightly "Coil Bind the Primary, which will cost you a slight bit on your top end) (These changes will progressivly increase your Engagement RPM)
Secondary Clutch: Move your Spring to hole 2, test it out. Move Spring to hole 1, test it out. (These changes will Decrease your rate of acceleration, and increase your rate of "Backshift" (Engine Braking). Be carefull when taking Clutches apart, comploments are under Tension and can come apart with LOTS of energy.

RD

[JohnF]

Hey, that was a while ago. I just read that last post of mine:

"Changing elevation should not require weight change ..."
That's wrong. Although the max power RPM does not change and it is true that the masses in the drive pulley are RPM sensitive the CVT as a whole is power sensitive and the max power of the engine changes with elevation.

So, what would I say today? First make sure everything is clean and lubed. Follow RD's advice above but with some understanding to fit your case.

Not everyone will need to change their engagement RPM. I drive a standard transmission Jetta (pretty light car) everyday. When air conditioner season first hits my highly calibrated left foot sometimes needs adjustment to raise the engagement RPM or I'll lug (and sometimes kill ) the engine. Same theory here, if you're lugging the engine then you need higher engagement RPM, if it hammers and/or spins tires when it engages then you need lower engagement RPM. The drive pulley is not as adaptive as my highly calibrated left foot so it is best to choose engagement for loaded condition (whatever your's are) and accept slightly higher engagement under other conditions. Especially so if you use tracks. RD's shim adds preload by slightly compressing the drive pulley spring. The downside he mentions is that the wire diameter of that spring is such that the drive pulley will coil bind before the pulley will fully shift out and you will have a slight drop in your highest drive ratio. I have been looking for the spring that will give the preload without the shims but these CVTech pulleys are not current (old version of powerbloc 50) and CVTech told me that they do not make the springs any longer; that I should experiment with powerbloc 80 springs and gave me a list of 4 to try. That's 'spensive so I instead decided to add more power at lower RPM so I could remove the shim. (in progress - stealth mode)

The numbered holes on the driven pulley affect the CVTs affinity for high or low drive ratio. The lower numbered holes skew preference towards low and high numbers towards high. I have the lowest geared transmission and drive in hilly conditions, sometimes with supertracks, and absolutely prefer the lowest settings here. I'm not sure I can tell the difference between 1 and 2 so I like either. This is especially the case on downhill legs as it gives me the ability to creep it down some pretty freaky slopes.

So far in my experience the settings you choose for the above two don't need adjustment with elevation change.

Now for drive pulley weights. At(ish) and below 3000ft elevation I run 260g weights. Where I ride in this elevation is hilly and I haven't had a chance to run the tracks but these weights work well.

At and above 8000 the 260g weights are a dismal failure. Last year (about this time actually) I went on a group ride in the mountains of WY on tracks and in the snow and frankly was a bit embarrassed by how poor the machine performed. I really had to work it to get it to turn, etc. At lunch I popped out my tools and a set of 225g weights and swapped. This improved RPM (from 1700 to about 2100 as I recall) and made it so I could at least turn in low gear easily, but still... This year I grabbed 200g and 175g weight sets and intended to experiment further but when I had time there was no snow and when the snow came I went to the Carribean and then ran out of time.

And now I have that stealth project going which will change everything.

Oh, "...to keep things simple..." Whaaattt?

[berky84]

Thanks for the reply, I'm headed out for my first big trip out here at the end of the May loaded down on super tracks towing a 6 wheeled argo tub trailer loaded down. From what i'm gathering the $30 primary spring replacement coupled with the secondary in hole 1 sounds like the set up of a work horse and the best place to start. My original issue was that in turns i was powering out, thinking it was a combination of the secondary wasn't down shifting causing a lack of power (correct me if i'm wrong but it is the secondary that does the majority of the downshifting?), as well as the engine only having 150 & 140 compression. Engine is rebuilt and should be back in by the end of this weekend And RD, thanks for the time you spent on your you tube video's, i'm a visual learner clutch rebuilding was a breeze!