Hydraulic clutch vanishes

[CBr6y]

Just looking for thoughts here ......

CB1300, all working fine a matter of weeks back, then a week ago it was taken out the garage and the clutch was gone. No warning, no previous slippage or issues whatsoever!

Now in many years of biking between us, neither of us have ever had a clutch go on us, let alone having had something suddenly disappear like this. 

Now normally you would expect that at the right revs, you would be able to shift  up and down the gears without too much trouble,  this also did not prove to be the case!!  Safe to say, we were not amused or impressed as only purchased the bike a few months back.  Anyhow, got bike to garage it was purchased from (shall reman nameless for now).

Picked bike back up today and it is running fine, and the answer we got was, the clutch fluid must have degraded.  We changed the fluid and its working fine.

Now does this seem right to anyone on here?  ........ bearing in mind that the fluid that was in it when it went in was crystal clear and light in colour, no floaters etc .... and it can clearly be seen that there has been no screwdriver anywhere near the screws on the reservoir, so how can they have changed the fluid? 

They appear to be hiding something so curious as to what could have caused the clutch to disappear like this?

[Alzo]

Moisture in the fluid....or air in the system and a quick bleeding has resolved the situation...but all said the lid of the reservoir would need to come off to do a complete bleed and refill...so they must have been real careful on removal.

[7550]

When you say the clutch was gone, do you mean the clutch lever had no pressure or it had pressure but wasn't disengaging the drive ?

[CBr6y]

Clutch had no pressure whatsoever

[Alzo]

Then moisture or air would have that effect.

[MOzZereLLa]

What about the slave cylinder? Seals?

[CBr6y]

It's all a bit odd. Garage really didn't want to discuss and stuck with the degraded fluid angle, and when we pushed it a bit yesterday the guy responded with ... 'ah well if you've left the bike bike sitting for a couple of days, maybe that's what's done it'  to which we responded, we leave bikes sitting for weeks if not months on end over winter periods, never had issues before.
Where we store the bikes now is a much warmer and drier place than where we used to have them, so don't have the same level of moisture/cold risk.

The bike is under currently under warranty, but from our perspective who says it won't just happen again out the blue as it did this time .... by which time warranty could be out, hence looking for thoughts on what could be underlying reason or just one of those things?

The garage attitude/responses makes us more suspicious, as they appear to be paddling for all they are worth.

[Alzo]

It's a basic hydraulic set up....so any failure is only attributable to air (seal  failure)....degraded lines...connections...or moisture....but moisture doesn't usually lead to full failure....just spongy.. No idea why the garage is being so coy....but I honestly don't think you have much to worry about...if you have no confidence in their fix then for peace of mind get it checked over elsewhere
A visual check and new fluid by yourselves if you feel so inclined.

[CBr6y]

Visual  checks already carried out ar the time it occurred,  couldn't see anything out the ordinary whatsoever. Garage confirmed in one of the phone conversations that slave cylinder had been checked and was fine/dry and no sign of any issues,

The bike will get checked over by a garage we know and trust for piece of mind, was just curious if anyone had any other ideas or had any experience of something similer, just on the off chance.

[Alzo]

No....

[DaveH]

I had something like this happen to the GPZ900, brought it out of the garage after winter to the same thing - no  signs of any leak. Got a slave cylinder of ebay went to change it but the clutch was working again and continued to work.

Still have no idea why it failed that one time

[CBr6y]

Spoke to our 'trusted' garage, and straight away he said its more than likley the slave cylinder being the root cause.

Says the cb13's are bad for it. Won't see a leak as such, it's more of a mist, and because if where it's situated it's not obvious due to chain spray. Advice is just to keep an eye on it as the likelihood is that it will happen again, if it does, time for a new slave cylinder.

Hey-ho   

[Green_Ninja]

I had something like this happen to the GPZ900, brought it out of the garage after winter to the same thing - no  signs of any leak. Got a slave cylinder of ebay went to change it but the clutch was working again and continued to work.

Still have no idea why it failed that one time

When i had the ZX10 (1990) I had the same issue turned out to be the seal in the slave cylinder and because of the position it's hard to see any leak and because it is affected by the heat cycles of the engine the fluid goes off much quicker.

[DaveH]

I never had to replace the slave cylinder or even bleed the clutch, it just worked without any intervention.
Can't remember checking if the clutch was engaged, could it have been stuck disengaged, giving the apparent feeling of no clutch action, it was just that the slave was already extended?

[MOzZereLLa]

Look into an Oberon slave cylinder. Should be better than oem and cheaper.