TimDH Posted January 29, 2022 Report Share Posted January 29, 2022 (edited) Sorry to start off here with a negative thread but I am having a complete mare with the rear brake on my 4RT. It's been a little problematic but no big issues until 2nd last time out when I did a big jump which split the res to MC pipe,fixed that and but it then refused to bleed even though we tried new MC parts. I replaced the MC with new and it bled easily enough,took it out again and the brake started binding as I guess in my desperation to get a brake I over adjusted it.Backed it off and pushed the pads back and no brake pressure no matter what we did. I have bled the normal way,reverse bled,used a vacum bleeder and some of the finest trials brains have given advice it just won't bleed. I have a new MC,tried a new hydraulic pipe and the caliper is 100 per cent not leaking.Every individual part works fine but I have no brake pressure at all. This is the most frustrating thing I've ever come across in 40 years of bike ownership and I used to race 2 stokes! Any help much appreciated as I'm at the point of breaking it for parts. Edited January 29, 2022 by TimDH Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted January 29, 2022 Report Share Posted January 29, 2022 (edited) I have had an issue like this once on my 07 4RT, from a drained system I was having an issue getting the air out even with vacuum and reverse bleeding. I ended up doing one last good reverse bleed and then having to pull the rear peddle off the bike lift the rear of the bike up with a strap and then pump the piston with a small rod (tip of a small screw driver) to get enough volume through the system to get the air out. Apparently there just is not 100% of the movement in the piston from the peddle and being able to fully push it in with the driver was all I needed. good luck. Edited January 29, 2022 by jonnyc21 Quote Link to comment Share on other sites More sharing options...
TimDH Posted January 29, 2022 Author Report Share Posted January 29, 2022 Thanks I will inevitably give this a go tomorrow,how on earth is this necessary though. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted January 30, 2022 Report Share Posted January 30, 2022 I wish I new why but I found that on all of my family trials bikes it has been easier to bleed the rear brakes this way. Daughters 06 Beta 80, Wife's 08 Gas Gas 125 (was the worst of the bunch), my 07 Montesa 4RT. I noticed your other post about reliability, you may want to double check your master dose not have a bur in the boar cutting the seal as well. I know of several people that had a buddy hone the bur out of the master and then have to put new seals into the Braktech masters. Good luck. Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 30, 2022 Report Share Posted January 30, 2022 You need to burp the banjo bolt on both ends of the hose. Just a quick loosening and retightning will get it moving. It helps if the caliper is higher than the m/c. Quote Link to comment Share on other sites More sharing options...
TimDH Posted January 30, 2022 Author Report Share Posted January 30, 2022 5 hours ago, lineaway said: You need to burp the banjo bolt on both ends of the hose. Just a quick loosening and retightning will get it moving. It helps if the caliper is higher than the m/c. We must have done that a thousand times. Quote Link to comment Share on other sites More sharing options...
TimDH Posted January 30, 2022 Author Report Share Posted January 30, 2022 5 hours ago, jonnyc21 said: I wish I new why but I found that on all of my family trials bikes it has been easier to bleed the rear brakes this way. Daughters 06 Beta 80, Wife's 08 Gas Gas 125 (was the worst of the bunch), my 07 Montesa 4RT. I noticed your other post about reliability, you may want to double check your master dose not have a bur in the boar cutting the seal as well. I know of several people that had a buddy hone the bur out of the master and then have to put new seals into the Braktech masters. Good luck. It's a new MC. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted January 30, 2022 Report Share Posted January 30, 2022 (edited) 1 hour ago, TimDH said: It's a new MC. The ones that my friend rebuilt where all brand new on new bikes... manufacturing defects happen and it might be hard to tell what lot or year the new one you have was built. good luck. Edited January 30, 2022 by jonnyc21 Quote Link to comment Share on other sites More sharing options...
lineaway Posted January 30, 2022 Report Share Posted January 30, 2022 5 hours ago, TimDH said: We must have done that a thousand times. Should only need to be done once. Use a clear 2-3 foot bleeder hose draped over the rear fender to see what you are doing and for gravity to help. Quote Link to comment Share on other sites More sharing options...
TimDH Posted January 30, 2022 Author Report Share Posted January 30, 2022 9 hours ago, jonnyc21 said: The ones that my friend rebuilt where all brand new on new bikes... manufacturing defects happen and it might be hard to tell what lot or year the new one you have was built. good luck. Ok thanks I'm leaving it until I come back from skiing or I may smash it with a hammer. Quote Link to comment Share on other sites More sharing options...
jrsunt Posted January 30, 2022 Report Share Posted January 30, 2022 Used to do this on 315’s as well as 4rt’s. Put the rear wheel on your workbench or as high in the air as possible. Usually bleeds up straight away Quote Link to comment Share on other sites More sharing options...
TimDH Posted January 31, 2022 Author Report Share Posted January 31, 2022 I couldn't resist another go before I go away. Thanks to those that tried to help but I still have no brake pressure despite trying the lifting of the bike method,all the parts are fine. On the plus side I resisited the temptation to smash it with a hammer. Quote Link to comment Share on other sites More sharing options...
jrsunt Posted January 31, 2022 Report Share Posted January 31, 2022 Stupid question, but have you enough free play on the pedal-m/cylinder if the brake pedal is still on? Also, the reservoir cap and rubber can seal too well not allowing fluid to be sucked through. They can be infuriating, keep at it. Quote Link to comment Share on other sites More sharing options...
jonnyc21 Posted February 1, 2022 Report Share Posted February 1, 2022 (edited) 13 hours ago, TimDH said: I couldn't resist another go before I go away. Thanks to those that tried to help but I still have no brake pressure despite trying the lifting of the bike method,all the parts are fine. On the plus side I resisited the temptation to smash it with a hammer. One more FYI on my comment about the issue with the master needing to be honed. The bur is small and cuts a very small scratch into the rubber seal that is only easy to see under a microscope or quality magnifying glass. Even at that size it is large enough to let in just a touch of air. I hope its okay to cross post from another forum, if so here is the thread on the exact issue I am talking about from ADVRider. (almost forgot one was over there)https://www.advrider.com/f/threads/braktec-master-cylinder-problems-why.1090928/ PS. I see the images on the 3rd page are not showing up for me any more, however they looked a lot like post 57. - https://www.advrider.com/f/threads/braktec-master-cylinder-problems-why.1090928/page-3#post-28052194 Edited February 1, 2022 by jonnyc21 Quote Link to comment Share on other sites More sharing options...
TimDH Posted February 1, 2022 Author Report Share Posted February 1, 2022 21 hours ago, jrsunt said: Stupid question, but have you enough free play on the pedal-m/cylinder if the brake pedal is still on? Also, the reservoir cap and rubber can seal too well not allowing fluid to be sucked through. They can be infuriating, keep at it. The sum total of brake pressure today is a slight movement of 1 piston and that's if I use a plunger on the MC piston. Quote Link to comment Share on other sites More sharing options...
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