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thanks for the reply , ive checked all brake lines all are clear . as its now a trike it only has one rubber brake line that goes from top of master cylinder to a metal tee then on to wheel cylinders all copper pipe lines, ive syringed brake fluid through all the pipes and all are clear. just put master cylinder back on again this morning after filling it with fluid in attempt to prime it. tried again to bleed rear brakes only pushed a few drips of fluid out but did notice as i pushed released peddle quickly fluid did splash up in reservoir thats all that happens , i cant understand whats going on with this as rubbers look ok M cylinder dont leak its not scored inside or blocked the whole system looks ok there dont appear to be a reason it dont work even back filled it think ill try get another M cylinder from somewhere

Hi all has anyone got any ideas what's wrong with my rear brake master cylinder for a 1980 gs 850 , firstly the bike is now a trike with reliant robin axle and drum brakes all new shoes and wheel cylinders. The reservoir had dirty fluid in so i thought id change it , I used a syringe to get mots fluid out without getting air in the system filled with fresh fluid and then tried to bleed rear brakes in the normal fashion, but no fluid would pump out , so i made a vacuum with a compressor to draw fluid out but then nothing came out and just squashed the pipe at bleed nipple. i thought something then was blocked so stripped it all down all pipes are clear stripped rear master cylinder , rubbers look ok nothing is blocked no leaks or scores in cylinder seemed all ok , put it all back , first used syringe to back fill rear brakes and pipes with new fluid till it came out of bleed nipples, locked them up then filled inlet and banjo outlet with fluid before tightening them up, connected reservoir and refilled. tried again both normal bleed and vacuum but still the same no brake pressure wont bleed and no rear brakes , gonna try easy bleed tomorrow but have doubts as if it wont vacuum from a bleed nipple as if it was blocked i cant see it pumped from reservoir working either. my conclusion buggered master cylinder or am i missing a trick with this . any ideas anyone

ok thanks seems its an upgrade then, perhaps its the box thats playing up giving me erratic movement on the rotor with the timing light fitted . the problem is im getting up till the engine get really hot backfiring in the exhaust and popping in the carbs IE you can see the carbs moving backwards as they make popping noise , tick over is ok, quick revving makes backfire slowing down, holding on 3to 5 thou reves makes backfires and the popping in carbs , so im not sure if its the carbs making the engine run ruff showing erratic advance movement or dodgy advance making engine run ruff, but when engine been running parked for 10 15 minutes it must be quite hot by then and it not as bad then but then im getting worried in case im over heating it. car engines are much easier. I have cleaned all the jets in carbs float levels checked all good compression is over 160 psi all 4 inlet boots now not leaking but do need new only thing not properly sonic cleaned is carb bodies im sure just that would cause all the problems

Hi all can any one help me as now proper confused, 1980 gs 850 GT electronic ign . I took off cover put a snap on timing light first on no 1 then on no 3 to check auto advance, both pic ups. appeared to be very erratic at tick over and higher revs. (now the confusion ) my Haynes manual says check the atu fittd to both electronic ign and points ign, so i undid the center bolt and took off what i call the rotor then the three screws holding the back plate removed the back plate and nothing is there just end of crank shaft and a small locating pin that fitted in the bottom end of magnetic rotor arm ive added some pics the rotor the pick ups and back plate and lastly what is behind them . have i got parts missing this may account for back firing etc or is there any other device that sets the auto advance . thanks for any help advice etc

thank you ,ive just sent grumpys a message , hope he can help

hi all i only joined OOS yesterday and have a couple of questions i need some advice with, so hope im in the right place. After a very long absence from bikes im now retired and an oap, but have now treated myself with a 1980 GS 850 GT Trike (electronic ign) 1st ive had carbs of cleaned all jets thoroughly and blown 160 psi of air through them (not with diaphragms fitted). tuning the air screws no 4 carb air screw has no effect at all. with the srew out engine running should this draw air through the screw hole ? mine does not if it should, would it be wise to blow air pressure to try unblock it 2nd while carbs were off i found the rubber inlet boots were quite hardish one was split and another had a very slight leak allowing wd 40 to seep through, i have temporally sealed them but obviously need a new set ive checked Google and Eblag etc and can only fined them in USA, im in Essex UK, is there any members who can point me in the best cheapest direction in or close to Essex to get a set, or will any from a later model fit my engine thanks for everyone patience reading this post and i apologise if ive put this in the wrong place thanks for any help with my questions