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Discussion Starter #1
hi Guys
i have bought (see my earlier sub ) a 97 no runner that was garaged for over 6 years
i have it running now and its ready to ride but for 1 thing
in the beginning the binding was quite hard as witnesed by the earlier fitted pads being worn almost to the metal
the front lhs and rhs calipers are still moderately binding on the discs and im not happy to ride it like that
i have isolated the issue to the front brake system only
(by trying the rear pedal only hard they release freely ) even though i have had the brake delay valve " pop" a couple of times before it freed up
so its definitely not the classic rear cbs issue

so what have i done so far
1 took out the outer pistons and cleaned them up and polished the surfaces with chrome polish to a mirror finish and taken out the seals and cleaned them up too
now they slide in and out easily

2 on both sides i have flushed the system and there is no air trapped the lever is pretty solid and needs little pulling in to activate the brakes the lever is not squishy

3 i have been working the pistons in and out repeatedly to force any air that might have been in the system into the msater cylinder reservoir and opened the lid
sometimes they go in with finger pressure and sometimes near end of inward stroke i need a lever ( at random)

4 continuing on this i have continued to do this and the amount of stick-tion has reduced somewhat but still binding

5 i am beginning to think that i have a duff master cylinder that is not letting the fluid back into the reservoir ( i had flushed this and drained out all the old fluid )

any thoughts on this are appreciated
paul
 

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3 i have been working the pistons in and out repeatedly to force any air that might have been in the system into the master cylinder reservoir and opened the lid
sometimes they go in with finger pressure and sometimes near end of inward stroke i need a lever ( at random)

This says to me that there is something wrong with the lever system, have you double checked by pushing in the centre pistons which should stay in?
If you have then you would be right to suspect the M/C ......... or the hoses.

The random nature suggests to me that there is a random plug of 'debris' that moves around hence the random nature of the problem. If there is 'debris' (could be black goo as often found in secondary cylinders/pcv) inside the hoses/mc then you need to dig in there and see what you find. The M/C pulls apart easily (probably need a service kit) but if a line has started to decay inside replacement is the only option. A quick check for lines is to pull them and push some suitably sized fishing line through, this should slide through with little resistance, if it doesn't then the hose should be replaced.
 

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Discussion Starter #3
hi Duck
thanks for the heads up
indeed the scenario seems to be pointing towards an obturation in the front master cylinder and or the front hoses
am i correct in thinking that the secondary master on the lhs fork is taking fluid and under load driving the fluid to the rear brake inner piston ?
in that case im doubting how a blockage there would affect the front outers ,
as i mentioned before the footpedal front inners are free and dont drag
look forward to your thoughts
paul
 

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hi Duck

am i correct in thinking that the secondary master on the lhs fork is taking fluid and under load driving the fluid to the rear brake inner piston ?
in that case im doubting how a blockage there would affect the front outers ,
....
paul
Yes that is how the secondary works on the rear brake (2 outers operated by the secondary).
If you are testing in the garage (not on the road) you can separate the front and rear circuits simply by not activating the foot pedal which operates the centre front pistons.
If you push the centre front pistons in they should not move if you just operate the hand lever. If you still have an occasional brake stick then you know you have an issue with the M/C or hoses.

I'm not suggesting that the blockage is in the secondary cylinder (or the PCV) simply using these as examples where the black goo often resides.
 

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Discussion Starter #5
hi Duck
thats clear
next thing im going to do is get a 2nd hand front MS and see if that makes things better
they only cost about 25 gbp so its a cheap bet
if thats not the solution ill start attacking the front hoses one by one
thanks again for your help
paul
 

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Discussion Starter #6
to recap
97 bike stood for nearly 7 years binding front brakes
curiously the rears worked ok after freeing the front linked brakes delay valve ( popped open) and then re popped it several times
and
cleaned and silicone greased the slider pins
all systems fully bled
but still binding at the front
now solved after a long process of trial and error
steps taken in the process
1 clean / polish all the outer front pistons lhs and rhs and remove and clean dust ring ad poke a wire through the channels
slight improvement but still stiff
2 take off master and clean it out and free up the tiny bypass orifice
slight improvement but still stiff
3 fit a 2nd hand master
still stiff
4 remove all front brake hoses and link tubes and blow clear, refit
still stiff
having failed to solve the problem i look again at the front calipers
this time i remove the main seals ( on all my other hondas i never had an issue with the main seals as they are always wet )
lo and behold
corrosion in the groove under the main seal
hard to believe but its true
i have no idea how water and air got into the system
cleaned out the rhs and all is releasing properly ( still re used the old seals as the ones i bought in the uk were stiffer on the pistons )
cleaned out the lhs and re used the old seals but still stiff , so will now go to honda and get the genuine outer seals
06541MZ 2405 for the smaller holes
06451GE2405 for the bigger hole ( as used on my cbr1000f so i have oem stock )

moral of the story
start with a full caliper rebuild and trust that nothing is correct...;
 

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To aid in reassembly, red rubber grease works great for inside of caliper. I like to slather the seal groove thinking maybe it'll keep from oxidizing.
 

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lo and behold
corrosion in the groove under the main seal
hard to believe but its true
Not that hard to believe, brake fluid is hygroscopic (attracts water) so old fluid will no doubt have some water in it. Leave it sitting in the system for a long time and corrosion will start. Add to that a failing dust seal and water can find its way in from the outside as well.
I was rebuilding the front caliper of my Honda XL600LM yesterday, both groves needed a good 'picking' to start with followed by a polish before the seals would sit correctly.
 

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Discussion Starter #9
hi Duck
what shocked me is that the calipers are made of cast steel and not alloy …
anyway its pretty much sorted now
some residual gripping was mostly eliminated by
1 drying out the slider pin holes ( a little too much silicone grease was creating compression )
2 changing the slider pin grommets which has swollen slightly
3 taking part of the bend off the anti chatter springs as they were pressing too hard on the pads and gripping them
4 sanding off about 1mm of material off my new( non oem ) pads as they seemed to be too thick and press the caliper pistons and sliders too far back
5 re bleeding again to get the very last tiny bubbles out of the system
now the residual friction is " almost normal " eg i can get about 1.5 turns from the wheel if i spin it by hand before it stops
before it would stop immediately
i guess the residual friction will gradually decrease as the pads and seals/ pistions bed in
lets wait and see….
 
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