CLUTCH LOCK??

[Kennyg]

if anyone could advise I've had this issue a few times.....usually at high RPM accelerations my clutch will go very stiff and remain disengaged (no drive to the wheel)  each time I have removed the clutch cover plate and taken the clutch spring and first plate off. Then I can manually force the pushrod back in, after that if reassembled it resumes operation. Why is the pushrod pressure increasing to the point where the clutch will not engage again.? This is a little upsetting to fix at the roadside.....but today I did just that.
I am assuming a return flow ? in the master is plugged although seal kits have been replaced at both ends of the clutch.    thx

[red]

if anyone could advise I've had this issue a few times.....usually at high RPM accelerations my clutch will go very stiff and remain disengaged (no drive to the wheel)  each time I have removed the clutch cover plate and taken the clutch spring and first plate off. Then I can manually force the pushrod back in, after that if reassembled it resumes operation. Why is the pushrod pressure increasing to the point where the clutch will not engage again.? This is a little upsetting to fix at the roadside.....but today I did just that.
I am assuming a return flow ? in the master is plugged although seal kits have been replaced at both ends of the clutch.    thx

Kennyg,

I am assuming that you have air or water in the clutch hydraulics, which expands to hold the clutch disengaged when you get things hot enough.  Your "fix" is probably just taking enough time to let things cool off, rather than doing anything mechanical.  Bleed the daylights out of that clutch slave cylinder, entirely replacing the old fluid with new fluid, by at least twice the capacity of the system, and see what happens then.  

If the slave cylinder is really corroded inside, you would need a new slave cylinder.  Hydraulic fluid absorbs water from the air, which can boil out (making steam) when things get hot.  Never leave any container of hydraulic fluid open to the air, longer than absolutely necessary.  Air expands when heated, also.  Some hydraulic fluid boils naturally, at temperatures higher than other DOT types.  Make sure you are using the correct DOT Type fluid that is needed by your bike.

Cheers,
Red

[racerrad8]

Does the clutch spring go over center?

Also, clean the pushrod behind the slave cylinder. The chain lube & road debris builds up and can cause it to hang up it the seal. Then the heat expansion of the rod might be enough to cause the problem.

Randy - RPM

[Kennyg]

Does the clutch spring go over center?

Also, clean the pushrod behind the slave cylinder. The chain lube & road debris builds up and can cause it to hang up it the seal. Then the heat expansion of the rod might be enough to cause the problem.

Randy - RPM


thanks to both and yes the spring seems to pancake right flat and it was just replaced??

[racerrad8]

thanks to both and yes the spring seems to pancake right flat and it was just replaced??

Flat is fine, over center is not. If it were going over center it would be concave the wrong way. You usually have to tap it with a hammer or drop it on the ground to get it to pop back.

Randy - RPM

[movenon]

You say that you rebuilt both cylinders. Did the problem start after the rebuild or was it there before you rebuilt the cylinders ?
George

[Kennyg]

The rebuild was last season but the engine and tranny were removed and overhauled just this spring??
new clutch plates and spring etc

[Kennyg]

thanks to both and yes the spring seems to pancake right flat and it was just replaced??

Flat is fine, over center is not. If it were going over center it would be concave the wrong way. You usually have to tap it with a hammer or drop it on the ground to get it to pop back.

Randy - RPM

Any issue in doubling up the clutch springs new and old for more strength??

[RichBaker]

That is the standard fix for the weak clutch spring....   

[ribbert]

That is the standard fix for the weak clutch spring....   

Only here.

I replaced a 100,000km old clutch spring with a new one and the improvement was only marginal. So a weak spring was not the problem. Replaced the fibres, as is the standard when they begin to slip, and it was like new. Put the old spring back in some time later while doing other work, still performs like new.

Even though my plates were standard thickness they become glazed and impregnated with crud and probably oil additives over time and that reduces the friction.

Adding a second spring does not compensate for a weak spring, it compensates for 'worn' fibre plates.

Yes the spring weakens over time, but unless it's been seriously overheated, not by much.

The standard order for fixing a slipping wet clutch is a set of fibres and if it still slips, new spring as well (it's uncommon to find worn out steels).

Clutch plates are a consumable like tyres and disc pads and need replacing when no longer serviceable.

The number of bikes I have worked on would be in the thousands, the number of different makes and models in the hundreds and unless something other than the water going down the plug hole in the opposite direction happens south of the equator, that's how it's done.

There will always be exceptions such as substantially increased power, clutch abusers, drag racers and certain oil users, in which case a doubled up spring is appropriate.

Motorbike clutch's are not very robust and are very prone to premature failure with abuse or just bad clutch habits. They are designed to do the job but without much reserve, to keep the lever as user friendly as possible.

The irony is a lot of people cite the cost saving of adding a second spring then go and spend more than the clutch pack would have cost on a M/C to overcome the extra pull required.

It is often said FJ's have weak clutches. Presumably they all leave the factory the same, the only variable being the user. I got 90,000 out mine (30,000 of that by the PO) and even then it only slipped slightly under the most extreme conditions, WOT, high revs, high gears and only then when the oil was not at it's hottest. I would consider that reasonable clutch life.
The plates were still the same thickness as the new ones.

Noel

[fintip]

If I'm not mistaken, there's a release valve that you can see if you pull the lid off of the clutch master reservoir, it releases 'bubbles' sometimes when the clutch lever is pulled, especially when bleeding; if that gets clogged, and it is small enough to clog, the lever can lock up, if I'm not mistaken.

Correct me if I'm wrong? I mean, for the pushrod to have THAT much resistance, when you have so much mechanical advantage over it through the hydraulic system... That would have to be VERY stuck, no? Doesn't this sound more like a hydraulic system failure?

Other option: Frozen slave cylinder?

[Pat Conlon]

Noel, there are so many errors in your post, I won't even begin....

To Kenny, the OP, many, many of us have corrected a slipping clutch by addressing the clutch spring.
If you have glazed fiber plates, yes, replace them...but you gotta ask yourself, how did they get glazed...from slippage? from the oil you are using?
If you have fiber thin plates, out of spec, yes replace them.

If your fibers are fine, and within spec, and your clutch is slipping (which many of us have found, except Noel) fix your clutch slippage by addressing your clutch spring....not by buying new fibers.

[ribbert]

Noel, there are so many errors in your post, I won't even begin....

To Kenny, the OP, many, many of us have corrected a slipping clutch by addressing the clutch spring.
If you have glazed fiber plates, yes, replace them...but you gotta ask yourself, how did they get glazed...from slippage? from the oil you are using?
If you have fiber thin plates, out of spec, yes replace them.

If your fibers are fine, and within spec, and your clutch is slipping (which many of us have found, except Noel) fix your clutch slippage by addressing your clutch spring....not by buying new fibers.

Yes.Yes, Yes, I agree with you 100%, 110%, fitting a second spring will overcome your slipping clutch woes!

The clutch is a simple device that relies on pressure and friction to operate efficiently. The two components that provide these are the spring and the plates. The bike leaves the factory with perfectly functioning clutch which gives many years and tens of thousands of miles of good service.
At some point it starts to slip. It is reasonable to assume that one or both of these components has reached the end of it's serviceable life. Therefore, if you replace those parts, you return it to as new condition. Simple.

I don't see how that is so wrong you "won't even begin...."

I wouldn't use the word glazed so much as contaminated or impregnated. As for the condition of my own clutch, it has never been allowed to slip and yes it was a brief encounter with synthetic that set it off and from which it never fully recovered but the same process would have happened at some point anyway. It's condition being entirely consistent with a clutch of that mileage that hasn't been abused or poorly used.

Your post suggests you don't acknowledge that the fibres become contaminated (as opposed to glazed) and lose friction and believe if they are in spec, they are serviceable.
Well, if we can't agree on that, further discussion is futile.

I  guess what offends me with this particular subject is not so much the mod itself or that some people choose to do it, but that it's defended and presented as a normal fix and, as a consequence, it's widespread use within the forum.
It also goes against the grain of 40 years experience fixing things properly.
A good repair should return the vehicle to it's best possible serviceable condition, or better. This mod fails that with the heavier lever pull.

I don't know what industry sources you have outside the forum that makes you sure enough to straight out tell me I'm wrong, apparently on many levels, rather than just having a different opinion but
if I'm wrong, as you suggest, then I've been deluding myself that years of training, schooling and decades of experience has taught me anything, even basic stuff.

I'm done with this subject. Challenging forum lore and suggesting it may not always be right is not well received.  Thís mod will continue to flourish as the "standard fix" within the forum and I'll stop worrying about other peoples bikes, let's leave it at that.

Pat, I am curious though about the "so many errors, I won't even begin..." .

BTW, who on earth are Kenny and the OP?

Noel

[Flying Scotsman]

Doubling up the springs is and should be recomended as it returns the clutch to better than stock working condition.
Saying that the lever pull is to hard is nonsense if thats the case you need to bulk up a little.i have 2 bikes with double springs and highly recomend doing just that.I have another bike with a barnet clutch and its fine but I like the double spring better.4th one has not been on the road yet but if it only has stock spring set up I will double up the springs even if the clutch does not slip.
Clutch lever is not much stiffer than 1 spring.