clutch problem

monty8563 · Mar 7, 2015

Hi all,
I hope that i am posting this in the right place, but here we go when riding my st1100 1998 the clutch works fine, but when in traffic and useing the clutch lots i end up with no clutch at all, if i pull over and let things cool down say 20mins or so clutch comes back. I have now replaced the clutch seals,dot4 and fitted a new b/ brake line im hopping this will put an end to the problem my next trip is at the end of march to London a round trip of 650miles we will see that happens, the next thing im getting is is i pull away on a very small hill i get a griding/knoking nose when on the more all is fine, if anyone can give me some pointer or if you have had the same please post i thankyou for any input you can give. Cheeres monty

ST1100Y · Mar 8, 2015

monty8563 said:
...when in traffic and useing the clutch lots i end up with no clutch at all, if i pull over and let things cool down say 20mins or so clutch comes back...

Sounds like air/water-vapour in the hydraulics, expanding due the engine heat, causing unintended actuation of slave cylinder...
- fluid replacement with throughout bleeding procedure (including wiping all parts of the reservoir-cover completely dry)
- rebuild of slave (& master) cylinder
- replacing clutch lines (minor leaking may cause water-vapour diffusing into the hygroscopic brake-fluid)

Brian Robinson · Mar 8, 2015

ST1100Y said:
Sounds like air/water-vapour in the hydraulics, expanding due the engine heat, causing unintended actuation of slave cylinder...
- fluid replacement with throughout bleeding procedure (including wiping all parts of the reservoir-cover completely dry)
- rebuild of slave (& master) cylinder
- replacing clutch lines (minor leaking may cause water-vapour diffusing into the hygroscopic brake-fluid)

I'm having a similar problem, I have been through the master clutch cylinder, replaced the seals with a complete repair kit, metal lines, must have bled a pint of dot fluid through the system. It's fine when cold and when i'm riding, but i stop for 10min or so, lost the clutch, it comes back once i have enough clutch to get into gear,[could be heat related but in winter when the temp gauge hardly moves?] so i come to the conclusion that it's the slave cylinder that there is a problem with. Is there a service kit for the slave cylinder?, been trying to find one listed to no avail. may try a new/second hand slave cylinder. And no leaks in the system, all new Banjo's, copper washers,ect!!!.

vinny · Mar 8, 2015

One question... when you say you have "no clutch" do you mean when you squeeze the lever, the clutch does not disengage, or after it warms up, the clutch will not engage? Two different problems. If the clutch is not "disengaging", then there is air or other contaminates, or leak in the system. If the clutch will not "engage" after working it a lot, then the return orifice in the master cylinder is blocked causing hydraulic pressure to build up and not equalized when the lever is released. Sitting a while allows the pressure to bleed down and then you have clutch again. Hope this helps.

monty8563 · Mar 8, 2015

It only happen when you have to use the clutch lots, the lever drops right back to the handle bar with no clutch at all if you let the whole bike cool down for say 20mins the clutch returns, when up and running all works fine, have fitted a braided hose, replaced the seals in the slave cylinder and bleed with new dot 4 oil.

I also get a gridding/knocking noise when pulling away or under load from a standing start all works fine when moving any idear whats happing here then??

Jim Van · Mar 8, 2015

ST1100Y said:
Sounds like air/water-vapour in the hydraulics, expanding due the engine heat, causing unintended actuation of slave cylinder...

That shouldn't happen if the bleeder hole in the MC isn't blocked with crud.

Jim Van · Mar 8, 2015

It sounds like the plunger in the MC is sticking and not returning to the released position.

It sounds like you have not dissasembled the MC yet. Correct ?

If not, I would dissasemble the MC, clean everything up, check the MC bore for corrosion, etc. Clean-up if necessary with 400 wet&dry and then re-assemble & bleed. I bet that fixes the problem. Make sure the MC bleed hole is clear.

monty8563 · Mar 8, 2015

Jim, when you talk of the MC what part are you talking about, i have striped the slave clutch part and replaced with new seal and cleaned the drain hole, is this what you mean?

Bush · Mar 8, 2015

MC = master cylinder, on the handlebar.

Jim Van · Mar 8, 2015

Bush said:
MC = master cylinder, on the handlebar.

+1 - That's what I meant.

BTW, I have disassembled several MC's in the past and re-used the original seal w/o any problems. The lip on the old seals still looked new. Cleaning up the bore & and getting all the gunk out seems to do the trick.

Finishing the job with "Brake Clean" does a good job of doing a final "rinsing" before lubing the plunger, seal, and bore with fresh brake fluid when re-assembling.

okbobw · Mar 8, 2015

monty8563 said:
Jim, when you talk of the MC what part are you talking about, i have striped the slave clutch part and replaced with new seal and cleaned the drain hole, is this what you mean?[/QU

Monty, Are you saying you rebuilt the slave on the front of the clutch cover.
I always rebuild them on any 1100 coming through my shop as that is a area that gets a lot of heat and any condensation usually turns the fluid in the slave cylinder to sludge.
What did you find in the slave cylinder?

So is your problem that the bike engine will rev and not go forward??? or is the bike still wanting to keep going when you pull the clutch lever all the way back to the handlebar?

The noise could be another issue but that would be internal and I don't think we should go there until you sort out the clutch working properly.

I might be inclined to favor the master cylinder on the handlebar as the problem

Jim Van · Mar 9, 2015

okbobw said:
Monty, Are you saying you rebuilt the slave on the front of the clutch cover.
I always rebuild them on any 1100 coming through my shop as that is a area that gets a lot of heat and any condensation usually turns the fluid in the slave cylinder to sludge. What did you find in the slave cylinder?

+1 to the above. I bought a spare slave cylinder off EBay and it was nasty inside ( rusty-like sludge ) after I dissasembled it. Much worse than any MC I have worked on.

monty8563 · Mar 10, 2015

Thanks, that bit i have not taken apart will take a look a.s.a.p

monty8563 · Mar 10, 2015

Hi okbobw,
The clutch works fine until you start useing it lots say when riding in the town, the clutcl lever drops back to the handlebar with no resistance if you stop on side of the road for say 20mins or so the clutch comes back, so i have rebuilt the slave cy on the outer clutch houses, i found inside a big billed up of crud and the drain hole at the base was block, cleaned all parts and replaced the rubber seals (3) off also fitted a new braded hose and bleed with new dot 4 oil.
The secound problem is when i pull away if i let the clutch out to quick it grides / knocks but only for a very short time as soon as you are moving all seems to be fine, if you can forward any idears this would be very helpful, i could live with it for a bit, but not looking forward to stripping the clutch out, lm thinking clutch plates?? Monty

Brian Robinson · Mar 12, 2015

vinny said:
One question... when you say you have "no clutch" do you mean when you squeeze the lever, the clutch does not disengage, or after it warms up, the clutch will not engage? Two different problems. If the clutch is not "disengaging", then there is air or other contaminates, or leak in the system. If the clutch will not "engage" after working it a lot, then the return orifice in the master cylinder is blocked causing hydraulic pressure to build up and not equalized when the lever is released. Sitting a while allows the pressure to bleed down and then you have clutch again. Hope this helps.

Hi, By "no clutch" i mean, nothing at the leaver, slack as a Monks pants. And playing "dumb" , i assume the master Clutch return orifice is the hole in the base of the master cylinder reservoir which is clear. i checked it this morning. I have ordered a set of Slave cylinder seals, so i will try those to see if the problem goes away. As for the heat question, i do notice that the two exhaust pipes on the r/h side go pretty close to the Slave cylinder, could heat be passed to it when parking up??. The heat shield does not go all the way around the exhaust pipe so i have lagged the pipe with Fiber Glass tape seal which was spare from my wood burning stove door. try anything once!!.

monty8563 · Mar 13, 2015

Brian, let me no how you get on with the fitting of the new seal and what you find in side when striped down, sounds like you have the same problem as me all the best monty

Jim Van · Mar 15, 2015

BTW, My clutch is working fine, but with 75K miles who knows when it may start to act-up ? I've been ordering some parts to have on hand and took a chance and ordered a set of clutch friction plates off a vendor on EBay. I possibly took a chance since it was a really good deal, but the plates look high quality to me - cork-based like the EBC plates. Who knows, may even be the same manufacturer.

Check the "Vendor Feedback" section in the "Buying/Selling, etc." section of the Forum for more details.

monty8563 · Aug 13, 2015

Hi all,
Here is an update on the clutch problem as talked about above, i replaced all parts in the s/cylinder ie seals x3 piston and bleed with new d.o.t 4 also replaced clutch cable with braided, this has fixed the problem and tested it on a 600 mile round trip to London were i did a fair few miles riding in London traffic clutch worked fine hope this helps. Monty

MSgJCarlson · Jul 16, 2020

I know this is and old threat, does anyone have a picture of where that return orifice is so i can without a doubt clean the right thing. Thanks

CYYJ · Jul 16, 2020

MSgJCarlson said:
...does anyone have a picture of where that return orifice is...

Hello, and welcome to our forum community.

Below is a picture of what I understand is called a "compensating port", perhaps this is the "return orifice" that you refer to. This picture is from a ST 1100, I am guessing that the ST 1300 would be similar. You can't quite see the tiny hole at the tip of the red arrow, the hole is underneath the round flat metal part. The little round flat part directly above the port is there so that fluid doesn't squirt up and hit you in the eye when you are working on the system with the master cylinder cover removed.

Fellow forum member @jfheath has written an excellent post that describes in detail exactly how the master cylinder works. He discusses the brake master cylinder, but I think most of the principles carry over to the clutch master cylinder. Here's the link to that post: Operation of the Master Cylinder

Michael

Compensating Port