Clutch free play changes when bike warmed up

Hello, Joe, Hope my recent experience will help. I have just gone through exactly the same as you describe. Clutch ok when cold but when engine warm the clutch lever travel increases to a point where it will not disengage drive and hence no clutch operation. I bled the system and still the same. As soon as heat was introduced the problem returned. I have owned the bike from new and changed the fluid every two years. There was no leak indication at the tell tale hole under the clutch slave cylinder. The problem was the clutch slave cylinder, I have replaced this and all is well. The reason there was no tell tale leak was that the area inside the rear engine cover was encrusted with dried fluid which I suspect had built up over a number of years and blocked the hole. In hindsight I would say there had been a very small leak and because I have changed the fluid often It never caused a noticeable drop in the master cylinder level. Strange as it may seem the problem came out of the blue, fine one day and failed completely the next. I am quite sure I would have picked up on any slight change in feel or operation of the clutch or lever. If you eliminate the suggestions above and decide to change the cylinder MaxPete has a great write up on how to do this in the ST1300 articles section. You do not need to remove the engine as the Honda manual says. Hope this helps.
Ed:)
 
I hear "I don't have a leak" far too often.
Just because folks don't see it, does not mean it's not leaking.
This month was clutch slave cylinder awareness month :rofl1:
 

Attachments

  • 20210516_202059.jpg
    20210516_202059.jpg
    127 KB · Views: 52
  • 20210518_151321.jpg
    20210518_151321.jpg
    101.2 KB · Views: 50
And for those of you about to do this job, I may be able to give you a couple pointers on a much easier way to do it with a few simple tools.
 
Thanks all for the advice. Just to make things interesting, I lifted the top of the master cylinder to check out the fluid, and cleaned off the corrosion around the mating surfaces, cleaned and dried the hard plastice cover and rubber diaphram (seems to have a few drops of condensation on it. Checked the fluid which looked a bit cloudy tbh and re-assembled. No problems since!. Will be flushing and refiliing the system in the next couple of days as having just bought the bike changing all the fluids and some basic checking of the systems.

Joe
 
Just an update - problem never went away. Did a fluid change yesterday, all working fine till the bike got up to temperature - by that I mean when the fan kicks in in traffic. Clutch won't disengage until lever about 25mm from the bar. All returns to normal when its cooled down. So best guess is clutch flexi pipe expandinf - so fix may be a braided hose.
Anyone with a similar experience? - A9 model just incase that makes a difference.

Joe
 
Yes. Check the brass Bush in the clutch lever. When you remove it, you will see a hole in the side. The push rod is supposed to fit inside that hole. My guess is that it was pressing on the outside. Mark the position of the hole with a felt pen on the top circle. It helps to make sure it is aligned.

If it is this, it is caused by the fluid expanding with engine heat and pressing on the slave cylinder. Normally the expansion is released through the tiny compensation port in the master cylinder but with the brass Bush permanently keeping the piston partly pushed in, the compensation port is blocked.

My A9 was delivered brand new in this condition. I commented that the lever felt tight and it was dismissed as being brand new. It got me 7 miles before I had to be rescued.
 
Last edited:
jfheath said:
Yes. Check the brass Bush in the clutch lever. When you remove it, you will see a hole in the side. The push rod is supposed to fit inside that hole. My guess is that it was pressing on the outside. Mark the position of the hole with a felt pen on the top circle. It helps to make sure it is aligned.

My A9 was delivered brand new in this condition. I commented that the lever felt tight and it was dismissed as being brand new. It got me 7 miles before I had to be rescued.
Click to expand...
I don't think thats the issue with mine as the clutch returns to normal operation once it cooled for 10mins. - If it was a bush issue it would stay in a failed state. Cheers for the thought.
 
Sorry. I hasn't spotted that I've contributed to this before ! I hate smartphones- far too small to read and type properly. Or I'm getting too old for this.
 
Congrats on the bike!
If your clutch function is normal when cold but an issue when hot, looks like your clutch slave cylinder neeeds attention/replaced. These can go bad by not flushing the fluid often enough.
I've never heard of anyone on this forum needing to put stainless braided clutch lines on their bike to prevent or remedy the problem you're having.
Good luck...
 
It’s got nothing to do with the lines.
As the engine warms up (heats up) the fluid struggles (thins out) and the rubber seals get soft and can’t do their job, tilting the piston just enough so that it’s metal on metal, and cause it to bind.
What your more than likely feeling is the clutch slave cylinder piston binding.
If you notice in this picture, the grey marks, are where the finish has been worn away from metal to metal contact.
 

Attachments

  • BCFCA3F7-66C7-4D37-A729-498A0E510C43.jpeg
    BCFCA3F7-66C7-4D37-A729-498A0E510C43.jpeg
    84.4 KB · Views: 36
Well 2 years later still not identified - However today after flushing the fluid and using a oneway bleed valve, I was able to study the action of the lever and piston in the master cylinder. I noticed that the piston was reluctant to push the lever back during bleeding. so i prodded around and freed it off and operation seems better. Once I'd closed the bleed valve the lever action was great. So planning a ride tomorrow to see if anything changes. I should look to see if I can find an exploded diagram of the master clyinder too.
Thanks all.

BTW I spoke to a guy that has serviced the master, changed the slave, added braided pipes and even rebuilt the clutch. Still the problem exists.
I suspect I need to contact someone who knows a cure for warts!

Joe - Loving his A9..most of the time!!!
 
Was the guy you spoke with, the guy who did that work on this bike?
If so, did he know what he was doing?
Its very easy to put the rubber bits on backwards on the MC pistons without knowing it, or not install and lubricate the slave cylinder correctly when putting it back together etc.
How was the system flushed and bled? Did you watch it being done?
I'll private message you a couple thoughts and things to try before I post them here to keep this post simple.
 
I had a similar issue on my 02 not that long ago. In my case, it was old fluid that needed a change. The problem got progressively worse over time until the clutch would no longer disengage at all (holding flat to against the bar, sitting at a junction, open the throttle and the bike would take off).

A simple fluid change sorted me out.

However, I have the master rebuild kit sitting in my garage, still in it's wrapping. From Honda that's a shade north of £100 for parts. Feel free to PM me an offer and an address. I'm happy to let it go for a reasonable price to a member here, and by reasonable, I do mean less than Honda charge (including postage).

Why the random generosity? Well... I bought a BMW K16.... doubt I'll ever need to use that part on my ST13...
 
I. Having the same issue, when it warms up, it creeps forward with the clutch lever pulled all the way to the bar and can't change gears when standing still, I have to be moving to get out of 1st or second to go to neutral. I rebuilt the slave and master, put new fluid in it, bless it several times with no improvement. I am almost to the point of replacing friction plates as I was told its " hydraulically locking up the friction plates" and a new set of frictions would help ...
 
Ajcole85 said:
I. Having the same issue, when it warms up, it creeps forward with the clutch lever pulled all the way to the bar and can't change gears when standing still, I have to be moving to get out of 1st or second to go to neutral. I rebuilt the slave and master, put new fluid in it, bless it several times with no improvement. I am almost to the point of replacing friction plates as I was told its " hydraulically locking up the friction plates" and a new set of frictions would help ...
Click to expand...
Mine did that when it got hot, to the point that stopping stalled the engine. The clutch lever travel was all free-play, with no resistance or clutch releasing. I fell over twice during my Ride Like a Pro class. Only cooling off made it return to normalcy.

Replacing the clutch fluid twice made all the difference. I used a cheap vacuum pump at the slave cylinder. The first change helped a lot, but the second time fixed it. I haven't noticed any more problems, regardless of engine temperature.
 
If the bike is creeping forward, then the clutch isn't disengaging.

If the clutch isn't disengaging it could be because:

  1. There is air in the system.
  2. The brass bush in the lever that pushes on the push rod has a blind hole and it has worn through. No longer blind.
  3. There is a build up of fluid in the slave cylinder housing poke the relief hole with a thin pointy thing. 6 o'clock on the slave housing.
  4. The fluid is squeezing past the piston seals in either the master or the slave.
  5. The pressure relief valve is blocked in the base of the fluid reservoir, preventing pressure from escaping when the lever is released.
  6. Crud has built up in the master cylinder, preventing the piston from returning.
5 and 6 are exactly the same issue that is reported when the SMC continues to apply the rear brakes when the brakes have been released.

Or sometimes it could be burring / distortion on the clutch plates or the basket - but this would happen when the fluid is cold.
 
jfheath said:
Or sometimes it could be burring / distortion on the clutch plates or the basket - but this would happen when the fluid is cold.
Click to expand...
What if, like mine used to do, it only happens when the engine is excessively hot, and returns to normal after cooling back to normal operating temperatures?

That must be due to fluid problems, like water vaporizing and then re-condensing, and not due to mechanical abnormalities that wouldn't change with temp.
 
That would be what mine is doing. Only does it when it's hot. The brass bushing in the lever is still ok, I cleaned out the CSC and it's housing when I rebuilt it, I thoroughly cleaned the master reservoir when I rebuilt that too ... I put my bike on the center stand when I bleed the clutch lines and I've done that about 3 times. I put a hand vacuum pump on the bleed nipple, pump it and crack the bleeder, top off the reservoir as needed. I even did it the old fashioned way by pumping the lever, holding it in, cracking the bleeder, locking the bleeder and pumping the lever again.... You know, wash rinse repeat.... What am I doing wrong?
 
You must log in or register to reply here.
Back
Top Bottom