drunkn munky Posted June 18, 2013 Report Share Posted June 18, 2013 Im having major trouble getting any decent feel in my brake lever, i have vacume pump which usually makes it a 5 min job, ive tried reverse bleeding, leaving the lever tied to the bar over night, holding the callipers above the res, ive bled the master cylinder end and i have clear fluid coming from both bleed nipples. I have GPZ750 forks and callipers (with anti dive blanked off), and a RC24 VFR750 master cylinder which according to this info are both matched http://www.rg500delt... bore sizes.pdf Doubting myself i went and drained/re-filled and bled both my NC and FZR which took no longer than just over 5 mins each so now im stuck for ideas, will dodgy seals on the master cylinder cause a soft lever? The brakes work but the lever comes back to the bar easily and doesn't feel me with confidence at all. Link to comment Share on other sites More sharing options...
porter_jamie Posted June 18, 2013 Report Share Posted June 18, 2013 try using a big syringe to force fluid in from the caliper end. this seems to usually work for me, as the air wants to go up, not down. open the lid and use another syringe to remove excess from the res. ideally 2 man job. Link to comment Share on other sites More sharing options...
drunkn munky Posted June 18, 2013 Author Report Share Posted June 18, 2013 Ive tried reverse bleeding with a syringe and got the same result Link to comment Share on other sites More sharing options...
porter_jamie Posted June 18, 2013 Report Share Posted June 18, 2013 oh. maybe it's just a shit brake - ie they might all be like it? bit like my gs500 one! Link to comment Share on other sites More sharing options...
-=JK=- Posted June 18, 2013 Report Share Posted June 18, 2013 edited due to my inability to read what you'd already done. nothing to see here Link to comment Share on other sites More sharing options...
Boozybloke Posted June 18, 2013 Report Share Posted June 18, 2013 Try taking the callipers part way off and pumping the pistons out a bit, then forcing the callipers back on? Also leave the lever lashed up for half an hour or so. Tried these both with my gs yesterday and they worked: only a little bit, but its a start? Link to comment Share on other sites More sharing options...
lorenzo Posted June 19, 2013 Report Share Posted June 19, 2013 Air trapped in the M/C? Crack the banjo off while you squeeze the lever, basically bleed the banjo on the master cylinder, using the actual bolt as a bleed nipple. Have plenty of rags to mop up! Link to comment Share on other sites More sharing options...
drunkn munky Posted June 19, 2013 Author Report Share Posted June 19, 2013 Master cylinder is bled using the above method. Maybe as jamie says there just meant to be like that, bloody crap brakes if they are. Admitantly im yet to ride the bike and like i said the brakes do work but i reckon it'll be a brown trouser moment pulling the bike up from any kind of speed. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 19, 2013 Report Share Posted June 19, 2013 Crap pressure seals. Link to comment Share on other sites More sharing options...
El Gringo Posted June 19, 2013 Report Share Posted June 19, 2013 Perhaps it wasn't just me then..... i couldn't get it any better than that. It does work but the retardation leaves a whole lot to be desired. The calipers were rebuilt with the existing seals and the vfr800 m/c wasn't a great match Link to comment Share on other sites More sharing options...
chrisexup Posted June 19, 2013 Report Share Posted June 19, 2013 i'd try a different m/c , could be the seals or just the feel that one gives...? Link to comment Share on other sites More sharing options...
drunkn munky Posted June 20, 2013 Author Report Share Posted June 20, 2013 Crap pressure seals. Presure seals meaning the piston seals? Perhaps it wasn't just me then..... i couldn't get it any better than that. It does work but the retardation leaves a whole lot to be desired. The calipers were rebuilt with the existing seals and the vfr800 m/c wasn't a great match It has a slightly different feel now too the VFR800 m/c that was on there, that one was dead soft until pumped a few times then you would get a half decent feel to them, as you say though that m/c didnt match the calipers so thats what i put it down to. The RC24 m/c i now have does match the calipers and the best i can get it is a ok feel to the lever, it doesn't go soft until pumped like the VFR800 one just a ok ish feel all the time. Maybe a strip down to investigate and new m/c seals will do the trick. Link to comment Share on other sites More sharing options...
marcaztls Posted June 20, 2013 Report Share Posted June 20, 2013 I think you're proving yourself that not everything you read on the 'net is right. My money's on the m/c being a bad match for the calipers in this instance, regardless of what the pdf. says. I've not read the full thread as I'm nearly out of tea but if you still have rubber hoses, clamp off the master cylinder lines just below it and if the lever's rock hard, there's nothing wrong with the seals in that. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 20, 2013 Report Share Posted June 20, 2013 Presure seals meaning the piston seals? Yes mate,sorry.. That trick that mark told you (clamp the hose) is a very good test. I also do this with braided lines as there is still rubber hose in the middle. Just have to be a bit careful (you can split the hose on the inside) But its a very good test. Link to comment Share on other sites More sharing options...
marcaztls Posted June 20, 2013 Report Share Posted June 20, 2013 Personally I'd be very careful clamping off braided lines as the inner hose isn't rubber, it's fairly rigid and brittle plastic. Link to comment Share on other sites More sharing options...
drunkn munky Posted June 20, 2013 Author Report Share Posted June 20, 2013 Braided hoses im afraid, not that i have anything to clamp them with anyway. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 20, 2013 Report Share Posted June 20, 2013 Personally I'd be very careful clamping off braided lines as the inner hose isn't rubber, it's fairly rigid and brittle plastic. I have done this a few times will no ill effects, and i was told it would not hurt them coz its rubber .. But i dont clamp them hard iygwim.. i just use pliers and squeeze with my hand. Ive seen people (inc a garage) use mole grips i suppose the plastic degrades over time and gets brittle as you say and could fracture.. i might stop doing that then.cheers for the heads up though mark Link to comment Share on other sites More sharing options...
lorenzo Posted June 21, 2013 Report Share Posted June 21, 2013 If you can get a firm lever by pumping it a bit first then that surely means that there's air in the system (or perhaps a knackered m/c), rather than it being a shitty match for the calipers? Link to comment Share on other sites More sharing options...
drunkn munky Posted June 21, 2013 Author Report Share Posted June 21, 2013 If you can get a firm lever by pumping it a bit first then that surely means that there's air in the system (or perhaps a knackered m/c), rather than it being a shitty match for the calipers? ? That was the previous non matching m/c cylinder that did that, that was changed for a matching one a long time ago, and it was never that firm just better than soft as shit. Link to comment Share on other sites More sharing options...
marcaztls Posted June 21, 2013 Report Share Posted June 21, 2013 If you can get a firm lever by pumping it a bit first then that surely means that there's air in the system (or perhaps a knackered m/c), rather than it being a shitty match for the calipers? Nine times out of ten, if you have a system with the original (or correct m/cyl) and calipers, and the lever needs pumping multiple times to get a decent pressure, it's because the caliper piston/s are retracting too much. This is usually caused by the seals sticking to the piston and as it's forced out by the master cylinder, it's 'sucked' back too far by the seal that's stuck to the piston so needs multiple fairly fast pumps to force the piston out past the stuck seal. A proper caliper service (and I do mean proper, just cleaning the exposed part of pistons isn't servicing your brakes but don't get me started on that...) should sort that. Very rarely, not very much these days at all in fact, it can also be that the piston seals are sided and chamfered in one direction, and they've been fitted the wrong way round causing too much piston retraction but like I said that's really rare these days. If you have a sliding style caliper, a soft lever could also be attributed to the slider mechanism. It could either be stuck, sticking or the rubber boot/s that the slider pins sit in have a vacuum in them (caused most often by people using the wrong sort of grease or worse, copper grease in them) which physically sucks the caliper back on the slider. I love brake problems me. Link to comment Share on other sites More sharing options...
El Gringo Posted June 21, 2013 Report Share Posted June 21, 2013 As a follow up to the above The calipers were completely stripped and rebuilt when i had them painted, original seals though and i don't remember if they ended up with dust seals in or not. The sliders were cleaned and lightly greased with the red rubber grease i used on the seals. I did look to see if there was a chamfer on the seal but i couldn't see one Could the VFR M/c be knackered too or was it a known good one Tony? Link to comment Share on other sites More sharing options...
drunkn munky Posted June 21, 2013 Author Report Share Posted June 21, 2013 No chris it was just one off ebay, looks in decent condition but the next plan of action is to get a rebuild kit for it. Stripping the calipers again isnt a problem although that would be a last resort as they seem to work fine, they move freely back and forth with no sticking and are clean as a whistle. Link to comment Share on other sites More sharing options...
gurninman Posted June 21, 2013 Report Share Posted June 21, 2013 I have done this a few times will no ill effects, and i was told it would not hurt them coz its rubber .. But i dont clamp them hard iygwim.. i just use pliers and squeeze with my hand. Ive seen people (inc a garage) use mole grips i suppose the plastic degrades over time and gets brittle as you say and could fracture.. i might stop doing that then.cheers for the heads up though mark The inner is PTFE tube - it's proper tough gear, and you should be able to clamp it as long as you don't do it too hard.It's not as malleable as rubber, so won't revert to it's previous form if you crush it.Biggest issue with PTFE tube is kinking, which can lead to cracks it it's kinked repeatedly..As long as you don't bend the line double , you should be OK. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 21, 2013 Report Share Posted June 21, 2013 The inner is PTFE tube - it's proper tough gear, and you should be able to clamp it as long as you don't do it too hard.It's not as malleable as rubber, so won't revert to it's previous form if you crush it.Biggest issue with PTFE tube is kinking, which can lead to cracks it it's kinked repeatedly..As long as you don't bend the line double , you should be OK. yeah as i said, i never had any issues when i have done it in the past, but then i dont go all silverback on it.Just gently squeeze hold in one hand while i operate lever in the other one.It is a very easy way to pinpoint if its a caliper (L or R) or a faulty MC. When i have done it i then squeeze it lightly on the opposite side to reform it and thats it job jobbed. Anyhow.. i still think its the seals that are toast. Link to comment Share on other sites More sharing options...
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