Clutch Pull

[El Camexican]

I installed 6 Heavy Duty EBC springs on my Tri-Z clutch recently and was concerned I may have over done it with 6 HD springs. OnF1 suggested 3 HD and three stockers and Raffa built some sort of extension, but it turns out they aren't bad at all. Maybe a little much for all day on a tight MX track, or bush trail, but not at all for short rides.

To give a comparison I took my bathroom scale and forced it against the lever to see what the max reading was while forcing the lever towards the bars. I got a reading of 12#. In comparison my KTM's with stock springs read 11#, my Duck with a fancy slave cylinder on it takes 10# and my Suzuki 1100 with HD springs takes 16# to close. I didn't check the stock Tri-Z, but it was the lightest of them all by far. I suspect the springs were weak.

Just thought I'd pass that on.

[YTZ drew]

Very clever using the bathroom scale, I love solutions like that!

[El Camexican]

Very clever using the bathroom scale, I love solutions like that!

Fish scale would be better, but I don't have one.

[onformula1]

Removed for one.

[barnett468]

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I installed 6 Heavy Duty EBC springs on my Tri-Z clutch recently and was concerned I may have over done it with 6 HD springs. OnF1 suggested 3 HD and three stockers and Raffa built some sort of extension, but it turns out they aren't bad at all. Maybe a little much for all day on a tight MX track, or bush trail, but not at all for short rides.

For future reference if you never need it, and I realize that you know at least part, if not most of this, the spring rate itself is basically irrelevant because once the lever has been activated/pulled, the clutch will spin freely whether they are 10 lbs per inch or 200 lbs per inch . . The only thing that matters, is the amount of force they apply when the lever is in the static/open position which is technically called the “clamping” force.

If you have a clutch that is slipping due to weak springs, you can often increase the clamping force enough to eliminate the problem simply by preloading the springs, and in some cases, the springs can be preloaded to the same amount of force a set of high perf springs like the EBC’s and Barnett’s would apply, and if you only needed the additional small amount of force that using 3 stock springs and 3 high perf ones would provide, there is absolutely no practical reason I can think of to run 3 and 3 as opposed to preloading the stockers.

Now, here’s the cool part, when this is done to light springs, the amount of force it takes to pull the lever in all the way gets progressively less by percentage compared to the high perf springs . . In other words, if both a light and a heavy set of springs apply the same amount of clamping force, the total amount of resistance/force the lighter springs will have will be LESS than the stronger springs will have when the lever is pulled far enough to fully disengage the clutch.

I know this works because I have done it to many race bikes for the reason you mentioned, which is that the heavier springs would wear my hand and forearm out because the clutch had to be used so much in the type of racing I was doing.

That being said, the springs AND clutch plates in my Tecate race bike were in fact not only stock, but they also had over 100 hours of endurance testing on them and they were preloaded very little, if any, and I hole shot several Pro races with it and it only slipped once, after which I installed new stock plates and it remained good.

The most difficult part of this entire process is just finding thin wall flat washers that will fit inside the hib and over the bosses on the pressure plate . . “AN” style washers often fit and are easy to find at many hardware stores . . There are also some copper washers that have very thin walls and they can often be found in the orange Dorman boxes or in the “Help” section of most auto parts stores . . If they don’t have them they can order them from Dorman . . Dorman also has a full online catalog.

You can also increase the length of the actuating arm on the clutch cover slightly but this will also increase the engagement distance/length, and depending on your particular setup, the clutch might not be fully disengaged when the lever is pulled all the way, however, most bikes have enough extra travel stock that some increase in lever travel will still allow the clutch t be fully disengaged.

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[El Camexican]

.For future reference if you never need it, and I realize that you know at least part, if not most of this, the spring rate itself is basically irrelevant because once the lever has been activated/pulled, the clutch will spin freely whether they are 10 lbs per inch or 200 lbs per inch . . The only thing that matters, is the amount of force they apply when the lever is in the static/open position which is technically called the “clamping” force.

Agree

.If you have a clutch that is slipping due to weak springs, you can often increase the clamping force enough to eliminate the problem simply by preloading the springs, and in some cases, the springs can be preloaded to the same amount of force a set of high perf springs like the EBC’s and Barnett’s would apply, and if you only needed the additional small amount of force that using 3 stock springs and 3 high perf ones would provide, there is absolutely no practical reason I can think of to run 3 and 3 as opposed to preloading the stockers.

The one reason I can think of (besides not needing to screw around with washers) is that as the pack wears I would rather have the stiffer springs in it instead of the old/light etc. shimmed ones.

.Now, here’s the cool part, when this is done to light springs, the amount of force it takes to pull the lever in all the way gets progressively less by percentage compared to the high perf springs . . In other words, if both a light and a heavy set of springs apply the same amount of clamping force, the total amount of resistance/force the lighter springs will have will be LESS than the stronger springs will have when the lever is pulled far enough to fully disengage the clutch.

Agree, and all the more reason I would want HD springs in a serer use application. As the plates warp and twist in the pack I would want as much resistance from the springs as possible, not something that would progressively offer less resistance.

.I know this works because I have done it to many race bikes for the reason you mentioned, which is that the heavier springs would wear my hand and forearm out because the clutch had to be used so much in the type of racing I was doing.

I could see that in MX. My needs have always been drag (pre-centrifugal lock-ups and sliders clutches, or at least pre the $$$ to buy one) and for most of the other riding I do the clutch isn't used much.

.That being said, the springs AND clutch plates in my Tecate race bike were in fact not only stock, but they also had over 100 hours of endurance testing on them and they were preloaded very little, if any, and I hole shot several Pro races with it and it only slipped once, after which I installed new stock plates and it remained good.

Stock clutch plates regardless of Japanese manufacture are always better than anything else out there. Not sure who makes them, but they are still the choice on a 300hp drag bike.

The most difficult part of this entire process is just finding thin wall flat washers that will fit inside the hib and over the bosses on the pressure plate.

Agreed. I have always had to drill and grind to do this. Another reason to just go with HD springs.

You can also increase the length of the actuating arm on the clutch cover slightly but this will also increase the engagement distance/length, and depending on your particular setup, the clutch might not be fully disengaged when the lever is pulled all the way, however, most bikes have enough extra travel stock that some increase in lever travel will still allow the clutch t be fully disengaged.

Agreed, but as soon as the plates warp a little it becomes hard to find neutral.

[barnett468]

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Stock 2 stroke clutches are engineered to slip a small amount from the factory it helps with wear on the transmission

Please explain in detail exactly how this reduces wear on the transmission because I have never heard of this before.

Also, please explain, why it would reduce wear on a 2 stroke transmission but not a 4 stroke one…Do they use softer gears in a 2 stroke trans?

Also please explain where you got this information and post a link to it if possible because I have never heard of it or seen it before.

smoother shifting,

Please explain how a slipping clutch provides smoother shifting since when the clutch lever is pulled in, the clutch is fully disengaged at that point anyway except for the very slight amount of drag that some fluids can create.

helps to keep the engine " On the pipe".

Please explain how a slipping clutch helps keep an engine ”On the pipe” since it would require an enormous amount of slippage to get an engine back "On the pipe" if it dropped below the rpm range where it had sufficient power to maintain speed or accelerate with sufficient speed, especially if it was a small displacement high performance engine like an 80 cc or 125 cc which could be referred to as being "pipey".

Please explain how the clutch gets as much slipping as it sounds like you are suggesting it does, then eventually provides full engagement, since it is not a centrifugal or torque converter type etc.

Some stock clutchs slip to much from the factory, a good set up when you add power can start slipping to much.

In my experience, if a clutch on a new box stock bike slips to the point of being noticeable when fully engaged, it is faulty and replaced under warranty.



In my experience, which certainly may not be as much as some others, during all the professional level racing I did for several years, I probably hole shot [or close to it], far more races than anyone else that did the same amount of races I did, and I didn’t do it with a slipping clutch . . Also, having actually worked with the engineers at Kawasaki, whom actually designed the clutches, and doing literally hundreds of hours of clutch testing while I was there, I can guarantee you with absolute certainty, that designing clutches that slipped once the clutch lever was fully released, was not part of their design criteria at that time, but perhaps they intentionally design clutches that slip now...I have no idea.

In fact, the clutch on the Tecate grabs so much [or slips so little] upon release that it chatters and squeaks . . The test clutches that did not chatter, slipped too much, so I decided to use the one that worked the best for the production, since the amount of time people spend taking off from a dead stop on an ATV, along with the amount of time they are ridden, isn’t enough to trade a clutch that engages positively upon release but has a little chatter and noise, for one that doesn’t chatter or make noise, but has a noticeable amount of slippage . . Noticeable clutch slippage was also not the case with the Maico, or Honda, or Suzuki, or Yamaha etc models I rode, which is probably more than 100 different types and/or years.

I have also never heard Jeff Ward or Brad Lackey or Jimmy White or Donnie Luce, or Wayne Rainey or Larry Roesler or any other Kawi guys, tell me, or anyone else at Kawi, that they felt the clutch slipping when they shifted . . When some of these races are won by just a few feet after 20 or 30 minutes of riding, and a clutch that slipped at all would reduce lap times, I don’t see the logic in designing a clutch that momentarily slips no matter how short the amount of time it slips is . . Also, for a clutch to slip enough to keep a pipey bike on the pipe, it would have to slip worse than a 1955 [or was it 1956] Chevy Powerglide trans that was low on fluid and has bad bands . . A motorcycle clutch is not centrifugal, nor are the ones I am familiar with, designed to work like one.

This being said, there IS a slight delay between full release of the clutch lever and full engagement of the clutch, however, in my experience, it is not intentionally designed in, nor is it hardly perceptible if it is perceptible at all, and is insufficient to create less wear on the transmission gears or keep a bike “On the pipe” as you claim . . In my experience, the primary purpose of this type of clutch is to provide immediate and 100% engagement upon release of the clutch lever just like an automotive clutch is which is used in vehicles that often have a much lower power to weight ratio than a motorcycle or ATV . . This is because any slipping of the clutch should be done by the clutch lever, or perhaps I and everyone else I know have simply been using it improperly in all these years.
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[bkm]

I broke 3 T-5 transmissions in my Mustang with a Spec-Stage 3 clutch. I switched to a less aggressive King Cobra pressure plate and never broke another. A less aggressive clutch is easier on a transmission, you know this.

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[barnett468]

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The one reason I can think of (besides not needing to screw around with washers) is that as the pack wears I would rather have the stiffer springs in it instead of the old/light etc. shimmed ones.

Since the stiffer springs would apply progressively less pressure on the pressure plate as the clutch plates wore compared to light springs that were preloaded to apply the same amount of clamping force, the clutch would slip sooner with the heavy springs, which is another reason why I have used the stockers in some cases and just shimmed them.

Agree, and all the more reason I would want HD springs in a serer use application. As the plates warp and twist in the pack I would want as much resistance from the springs as possible, not something that would progressively offer less resistance.

I don’t understand what you are trying to say here but if your plates warp, they will increase the amount of pressure on the pressure plate . . In other words, warped plates would have the same affect regarding increasing pressure, as adding an additional plate, although it would be a very thin one, however, the amount of force/resistance even excessively warped plates will have, or the amount of force it will take to make them all flat, is only going to be around 10 lbs at the very most in my experience.

Agreed, but as soon as the plates warp a little it becomes hard to find neutral.

This is why I mentioned that it only works on some bikes . . You just need to see how much lever travel you have left after your plates are hot . . If it is at least 1/3 rd or more, then you can lengthen the arm at least a little . . I have had to do this on a few bikes which is one of the reasons I know it works on some.
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[barnett468]

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I broke 3 T-5 transmissions in my Mustang with a Spec-Stage 3 clutch. I switched to a less aggressive King Cobra pressure plate and never broke another. A less aggressive clutch is easier on a transmission, you know this.

First of all, you are not comparing apples to apples.

Secondly, let me ask YOU two SERIOUS questions.

Do you honestly believe that a 2 stroke clutch is designed to slip so much that it will work like a torque converter or the clutch in John Forces car, and keep an engine “on the pipe”.

Have you ever ridden a box stock brand new 2 stroke motorcycle or ATV that ever did this, and if so will you please tell me exactly which one, or ones, they were so I can avoid buying them?

[bkm]

Did I say anything about "on the pipe"? You're reading to far into what I said so don't drag me into that argument. I stand by what I said, and what I said only.

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[barnett468]

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Did I say anything about "on the pipe"? You're reading to far into what I said so don't drag me into that argument. I stand by what I said, and what I said only.

What you said doesn’t mean anything because you did not post all your cars specs, therefore we can’t really determine the most likely cause of the failure . . Just because you claim it was the clutch that caused the trannies to break, it doesn’t make it so, and I can assure with a very reasonable amount of certainty, that your stage 3 clutch did NOT cause the trans failures, but exceeding the load rating of the trannies most likely did.

Having been partners in one of the biggest vintage Mustang repair and restoration shops in the Western US for around 20 years, I have found that in many cases, the part a person claims was the root cause of a failure, was not the cause at all, but merely a symptom created by the cause . . This is the case with the many of the Pertronix I ignition module failures, because for whatever reason, some people leave their ignition key in the run position with the engine off, which will in fact kill the unit . . Also, some people throw a big roller cam and AFR heads etc on an engine with old cast pistons and rods with stock rod bolts etc, then rev em to 6800 rpm and blame the rods and pistons for the failure when they come thru the side of the block.
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[bkm]

You just made my point. I never once said the spec clutch was the number one reason I broke transmissions. I most certainly was exceeding the limits of the transmissions and by switching to a less aggressive clutch, I was able to make them live after that. Nothing else was changed. I took the advice of an experienced local transmission builder and never had a problem for the rest of the time I owned the car. You can try and spin it any way you like, write a 300 page novel, break out your molecular properties hand book, get down to oil viscosity. I know for a fact that the less aggressive clutch was easier on my transmission. I know you're the smartest person in the room, I don't even have to ask you because you'll tell me, but you're not convincing me otherwise here.

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[barnett468]

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You just made my point. I never once said the spec clutch was the number one reason I broke transmissions. I most certainly was exceeding the limits of the transmissions and by switching to a less aggressive clutch, I was able to make them live after that. Nothing else was changed.

Actually, you just made my point.

A less aggressive clutch is easier on a transmission, you know this.

A clutch that slips enough to keep an engine “on the pipe” or reduce the load on the trans to that of the mfg’s spec if you have a high perf engine, will be FAR easier on the transmission if one revs the engine and dumps the clutch, but that’s simply not realistic . . In fact, you could probably put a 351 Windsor stroked to 393 or 428 with a 245@ .050” duration cam and Kenne Belle twin screw supercharger in your car with 28” slicks and a box stock T5 and rev it to 4k and dump the clutch and it wouldn’t break the trans, but I’m kinda guessin that you oughta bring yer lunch with ya cuz your 1/4 mile et might be measured in minutes instead of seconds if you did.

I broke 3 T-5 transmissions in my Mustang…

Ok, what is wrong with this statement above? . . If I broke even one T5 tranny, I would have stopped there and figured out why then corrected the problem instead of simply buying another one . . If I broke TWO T5 trannies in the same vehicle, I definitely would have stopped there and figured out why they broke and corrected the problem instead of simply thinking that “The third times the charm.” and buy another one and hope for the best.
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[bkm]

I swear you give me a fawking headache. I didn't say anything about "keeping the engine on the pipe" stop referring to that. Why do you keep trying to make a mountain out of a mole hill? I made a simple fawking statement that a less aggressive clutch is easier on a transmission. Nothing more nothing less. Anything is only as strong as it's weakest link and when the transmission is not strong enough to absorb the shock from the power of the engine delivered by the clutch, it breaks metal parts. I lived it first hand. What I did as a teenage kid with limited funds to get my car back on the street for the weekend has nothing to do with discussion so leave it out. I'd do a lot of things different today than what I did 20 years ago. For my sanity I'm finished here. Maybe someone else will join in and you can over analyze their statement and give them a damn aneurysm like you've given me.

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