Alex_H Posted June 19, 2012 Report Share Posted June 19, 2012 Yo all, was at a track evening today at doni (not my track it seems, pranged it last time) and a few minutes from the end of session 2, had a small wheelie out of the loop, came down and the brake lever was harder going into the next corner. At the end of start finish straight my brakes locked on hard so I had to get it off the track for obvious reasons. Session was cancelled because of this After a few mins, the lever came back and worked. I didn't go out again just incase. Anyone ever have this happen? And what was the cause? Its an ISR radial master cylinder hooked up to 09 R1 6 pots. Never had any trouble at the last trackday after lots more sessions. Any help appreciated before I melt the fucker down lol. Link to comment Share on other sites More sharing options...
ronenige Posted June 19, 2012 Report Share Posted June 19, 2012 make sure you've got some free play on the front brake lever Link to comment Share on other sites More sharing options...
bikecat Posted June 19, 2012 Report Share Posted June 19, 2012 as above but also check there's not too much fluid in the reservoir..( soak a bit up with some kitchen roll if it's right up near the top)..this can happen if you've topped up the system on worn pads then changed the pads which shoves the pistons back a bit then pushes the fluid back to the reservoir.. Link to comment Share on other sites More sharing options...
Alex_H Posted June 19, 2012 Author Report Share Posted June 19, 2012 seen this a few times and its always been a problem with a different lever being fitted to the master cylinder or an issue with a lever refitted incorrectly, so that's where i'd start Tis an ISR one so I don't think it can that really, it moves plenty freely Link to comment Share on other sites More sharing options...
CMSMJ1 Posted June 20, 2012 Report Share Posted June 20, 2012 too much fluid then? Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 20, 2012 Report Share Posted June 20, 2012 Clean your calipers.. make sure the piston move in and out freely.. it could be that the pistons are not retracting proplerly.. OR it could be you fluid boiling.. What are you using?? dot 4,5.1 or racing fluid (dot 5.0) how long since fluid was last changed? if it has water in it this will boil before the fluid does and will cause the same symptoms.. Hope that is some help to you. Link to comment Share on other sites More sharing options...
MonkeyJim Posted June 20, 2012 Report Share Posted June 20, 2012 Put some grease on the discs. for god's sake don't put it on the pads! just the discs, ok? HTH Link to comment Share on other sites More sharing options...
Alex_H Posted June 20, 2012 Author Report Share Posted June 20, 2012 Put some grease on the discs. for god's sake don't put it on the pads! just the discs, ok? HTH This had just crossed my mind, to the shed with the LM I go! lol The fluids about 6 months old, Dot 5.1 halfrauds. I'm going to take the calipers off later and make sure everythings moving ok. Got a funny feeling it'll all be free though. The fluid levels just above low marker so plenty of room in there me thinks. Link to comment Share on other sites More sharing options...
Pierre Posted June 21, 2012 Report Share Posted June 21, 2012 I fitted some cheap shite chinese ebay levers after falling off and promptly forgot about them till next trackday. When you pulled them, the brakes worked but after a couple of corners on the sighting laps they were virtually locked solid. I drained all fluid and bled through a couple of times, but it would do the same thing. Found that if i pushed the lever away from me the brakes released.DOH Funny thing was , when I compared them to OEM ones, I couldnt see even a small difference but in the bin they went. What I'm trying to say in a roundabout way is maybe try an oem lever again to prove the ISR one? Link to comment Share on other sites More sharing options...
srad34 Posted June 21, 2012 Report Share Posted June 21, 2012 This does sound very similar to my Duc when I fitted aftermarket levers. The adjustable bucket/pushrod was adjusted too far and this stopped the fluid returning to the master cylinder and as the brakes heated up, the front locked up bloody quickly. It took a couple of hours to figure it out but a tweak of an allen key sorted it, apparently it happens quite a lot according to that there tinterweb.... Link to comment Share on other sites More sharing options...
Benji Posted June 21, 2012 Report Share Posted June 21, 2012 Funny thing was , when I compared them to OEM ones, I couldnt see even a small difference but in the bin they went. What I'm trying to say in a roundabout way is maybe try an oem lever again to prove the ISR one? It's an ISR master cylinder with the lever that iSR supply with it, they don't make aftermarket retrofit levers. Link to comment Share on other sites More sharing options...
Pierre Posted June 21, 2012 Report Share Posted June 21, 2012 I realise that , i saw the pretty picture . But before he starts stripping down calipers I was suggesting (in poor cse-level english) that going back to a standard lever would quickly show if there was a fault with the ISR. Mind you, he'd probably have to test this by doing a few hard landing wheelies Link to comment Share on other sites More sharing options...
Tomfoolery Posted June 21, 2012 Report Share Posted June 21, 2012 I don't think standard levers fit ISR master cylinders. And they're very well made I'd be surprised if it were that. Link to comment Share on other sites More sharing options...
ronenige Posted June 22, 2012 Report Share Posted June 22, 2012 Just put the standard MC back on and try it , at least you can isolate whether its a fault at the top or bottom Link to comment Share on other sites More sharing options...
HeadtheBall Posted June 22, 2012 Report Share Posted June 22, 2012 I don't think standard levers fit ISR master cylinders. And they're very well made I'd be surprised if it were that. I think that he was referring to the lever that comes with the ISR M/C. Something caused the brakes to gradually lock (and it wasn't brake pixies). It *could* have been fluid expansion in the system as the fluid heats. Removing the master cylinder would eliminate it from the equation. The other thing to look at is the caliper condition. If the pistons are grungy and the seals in poor nick, then the piston could have seized, causing the pads to rub against the disc and overheat everything. I've seen it happen on a Kwacker with shitty 6-pot calipers Link to comment Share on other sites More sharing options...
Alex_H Posted June 22, 2012 Author Report Share Posted June 22, 2012 Cheers for the replies dudes. I don't think its the lever as such, but it could be an issue with the cylinder, so as I havn't got a spare MC to try, I'm going to have it off, throw a new seal kit at it while its off and obviously make sure its totally and properly clean. I can't imagine it'd take a lot to block the fluids return path. It's either that or I did actually boil the fluid, by way of maybe excess moisture in the system, would that do it? Is 5.1 prone to it? I've had the calipers off and checked all the pistons out, and all move freely and are pretty clean, as I think you'd expect on a caliper thats only 3 years old. I gave them a go over to remove some little bits but I dont really suspect them. Link to comment Share on other sites More sharing options...
CMSMJ1 Posted June 22, 2012 Report Share Posted June 22, 2012 5.1 is more prone to it than dot4. needs refreshing more often I do believe. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 22, 2012 Report Share Posted June 22, 2012 Dot 5.0 is the only one that dont absorb moisture. its silicone based,but is a biaatchh to bleed,the Army use this as they can leave the stuff wothout worry of getting water in the system. CMSMJ1 is right though dot 5.1 is more prone to hygroscopic behavior than dot 4.0. Link to comment Share on other sites More sharing options...
lorenzo Posted June 22, 2012 Report Share Posted June 22, 2012 It's either that or I did actually boil the fluid, by way of maybe excess moisture in the system, would that do it? No, I don't think so. I've overheated brakes in the past and the problem has been that the fluid boils and creates gas in the system, which essentially means you have to bleed them again and feels like you've just filled the system up but haven't bled them properly. Lever coming back to the bar, sloppy brakes, that sort of thing. In my experience just plain overheating from sticky brakes wouldn't do the same as what you've got. As a tester, I bet you can pick up a master cylinder with a lever for about £25 off ebay, something like an early r1 would be ideal as they're quite nice feeling without being radial, and hence pricier as an 'upgrade' on an older bike. Link to comment Share on other sites More sharing options...
ronenige Posted June 23, 2012 Report Share Posted June 23, 2012 but is a biaatchh to bleed, ????????????? , perhaps what you were bleeding was a tad awkward but surely ( in this case ) a fluid is a fluid is a fluid ???? Link to comment Share on other sites More sharing options...
Benji Posted June 23, 2012 Report Share Posted June 23, 2012 Is there a rubber dust cover on the master cylinder, have heard of people having problems with these before through dirt ingress. But equally that wouldn't cause the brakes to be coming on. Link to comment Share on other sites More sharing options...
BudgetBoy Posted June 23, 2012 Report Share Posted June 23, 2012 ????????????? , perhaps what you were bleeding was a tad awkward but surely ( in this case ) a fluid is a fluid is a fluid ???? No mate,, Dot 5.0 will hold air but not moisture. hence a bitch to bleed and get all the air out. Link to comment Share on other sites More sharing options...
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