mattycoops43 Posted June 13, 2014 Share Posted June 13, 2014 Hi peeps.Bit stumped here, I have come across the same problem on two different bikes which we can't work out.One is the hydraulic clutch on a custom intruder and the other is a hydraulic rear brake on a trike with a reliant axle.Both do the same thing, all rebuilt calipers on the trike, new master cylinder and slave on the clutch, both bikes ride fine when cold, but as the brakes heat up, the system pressurises and they gradually lock on, if you disconnect the linkage from the slave cylinder it will release enough pressure to free up and the clutch on the intruder is fine till the engine is properly hot when the clutch starts to slip and all the freeplay at the clutch lever disappears, if you crack the bleed nipple and do it up again, some fluid comes out and the clutch starts to work again.Not exactly the same systems I realise, but the problem seems to be very similar. Has anyone come across this? I have never had to strip a master cylinder but was wondering if there is some kind of groove which means that at fully open position it allows fluid past the seals to allow for pad wear etc. No idea if this is the case but trying to think of ideas that would explain a hydraulic system self pressurising? I thought if that was the case and you had the wrong piston travel at the master cylinder it might not allow fluid to equalise after each stroke, but that really is a guess.Intruders have a rep for bad clutch, and people say it's air, but this has been bled, reverse bled, bled with the slave up high etc etc a load of times. We could be wrong but think there is no air in there.Any ideas welcome really. Quote Link to comment Share on other sites More sharing options...
Tango Posted June 13, 2014 Share Posted June 13, 2014 Fresh brake fluid Matty? .....if it's absorbed any water, that will expand when it gets hot, causing these sort of probs.... Quote Link to comment Share on other sites More sharing options...
Chrissb6 Posted June 13, 2014 Share Posted June 13, 2014 Any moisture that's in the oil will expand as the calliper heats up causing the piston to stick on. Flush the lot out with good quality fresh oil Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 13, 2014 Author Share Posted June 13, 2014 Yup good thinking, the bike has only done 200 miles since built, but it was a long time in the building, not sure how long it's been in there. Quote Link to comment Share on other sites More sharing options...
Tango Posted June 13, 2014 Share Posted June 13, 2014 Yeah....brake fluid absorbs water....so, fresh fluid may sort it mate..... Quote Link to comment Share on other sites More sharing options...
Stu Posted June 14, 2014 Share Posted June 14, 2014 This is a common problem on the tlr so it could be the same issue The return hole in the master cylinder could be blocked up not allowing fluid to expand out of the lines Sometimes they need a poke with a bit of thin wire to unblock them Water would just make the fluid boil quicker and expand quicker but blocked holes in the master will stop the fluid going anywhere Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 14, 2014 Author Share Posted June 14, 2014 Thanks Stu. It's hard to describe, but it really does FEEL like fluid not returning. Quote Link to comment Share on other sites More sharing options...
Tango Posted June 14, 2014 Share Posted June 14, 2014 I'd start with the easiest thing Matty.....then go from there if that don't work......so, if it were me, I'd put fresh fluid in and see what happens.... Quote Link to comment Share on other sites More sharing options...
eastanglianbiker Posted June 14, 2014 Share Posted June 14, 2014 i would go with stu on this one as the more you are applying the pressure the more fluid is going to compress to where it will have nowhere to go once u open a pipe/nipple its then doing the job of the return hole in the master cylinderso as you have got to drain that to check do both jobs at t he same time drain fluid check return in master cylinder then top up with fresh fluid and rebleed Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 14, 2014 Author Share Posted June 14, 2014 Had a chat with Simon this morning, we both think you're all on the right lines, but he showed me in the manual there is a cable version, and it is a little unit mounted on a plate that is the same base as the slave cylinder and it's all self contained so because hydraulic clutches are generally a pain, he is just gonna change it. I don't blame him, they do seem rather hard to bleed. Quote Link to comment Share on other sites More sharing options...
Fozzie Posted June 14, 2014 Share Posted June 14, 2014 It's almost certainly got to be water in the fluid if it's only doing it when hot!Happened on a bike where the fluid was so old it had gone beyond the brown colour to black mould. Bleeding is easier than brakes usually, bleed nipple on the clutch end just needs a pipe attached, then pump the clutch lever and bleed the same as brakes, but access is easier and usually there's less piping running fluid to it. But if a cable conversion exists then I do advocate for that instead. Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 25, 2014 Author Share Posted June 25, 2014 Update for you guys.After stripping the master cylinder and relieving the equalising hole, put it back together and saw that the lever was pushing on the piston just enough to close the valve over said hole. Easy fix, Guessing it's not the right Lever? Just shorten the business end of the lever slightly and job done. Quote Link to comment Share on other sites More sharing options...
Stu Posted June 25, 2014 Share Posted June 25, 2014 that was going to be my next suggestion was take a look at the lever its a common problem with cheap chinese levers! more so on the brake though!!! I have heard horror stories where people fit them then so far down the road the brakes start to apply themselves due to the heat build up!!! not a good combination!! Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 25, 2014 Author Share Posted June 25, 2014 It's an original lever and original master cylinder. A brand new piston was bought for it, and part of the piston is a short intermediate link rod and this was 1mm too long. Quote Link to comment Share on other sites More sharing options...
Fozzie Posted June 25, 2014 Share Posted June 25, 2014 Sometimes 1mm makes all the difference Quote Link to comment Share on other sites More sharing options...
mattycoops43 Posted June 25, 2014 Author Share Posted June 25, 2014 Oh, and it was all brand new internals from Suzuki I found out today, so it looks like the build quality on their brake components is the same as their bodywork and paint! Quote Link to comment Share on other sites More sharing options...
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