Front Brake issue

Laverdalothar

Laverdalothar

Hero member
Location
Germany
Morning gents,

while driving to the MOT, the front brake almost locked just under riding. Lucky enough, I recognised it early enough to stop, but at that time, you could not even push the bike forward anymore. After cooling down, the brake released the front wheel again and I could load the bike on the trailer back home.

having it on the bike lift now and having taken off both callipers (while they are still connected to the brake lines and the brake master), I could push each of the 4 pistons in easily on each side. However, this caused the other sides calliper to push the pistons out. If I block one side, I can not pus the other side in, which makes me think that there is an issue with the master cylinder, not with the callipers (fluid not going back into the reservoir).

Would you gents agree I should start taking the master apart rather than the callipers? Any other points I should look at first? I have the small original distributor on the front of the lower tripple clamp in place but am quite Sure that is the wrong place to look at, right?

thanks in advance
 
Having just gone through a front brake issue on mine I would check both calliper pistons for corrosion (if they are steel) and overhaul and replace service parts as required.I replaced mine with the Teflon coated alloy pistons, and it is also suggested to overhaul the master cylinder at the same time then you are assured of a fully serviceable brake system and you only have to drain and bleed the system once.

Schurmy  8)
 
Lothar it sounds like the port in the master cylinder is blocked. Also check you have free play in the brake lever which would also stop the piston coming back far enough to open the port.

HTH

Ian
 
Hi
    It sounds like you have a partially blocked brake hose. I had a similar problem on my 3C, I put the brake on and the pads would only release slowly. I tried everything, checked the calipers all okay, even changed the master cylinder. I then removed the brake lines to find one side blocked, used a compressed air line to blow it through, problem solved.  Worth a check.
                                                                                                        Alan.





 
Laverdian said:
Lothar it sounds like the port in the master cylinder is blocked. Also check you have free play in the brake lever which would also stop the piston coming back far enough to open the port.

HTH

Ian
Click to expand...

Spot on, Ian...  ;)

After I wrote here, my brain worked further and I decided to take the master off first. Trying to blow into the hole where the line connects to, I could not press any air through it. Dismantling the masters lever, I thought: "Mmmh - that is a bit much resistance and a bit to much travel backwards of the piston... I blew some air through the same hole and - voila - the air passed without resistance! Put the lever back and the resistance was there again. Turned the adjuster screw backwards half a turn and now the air goes through with the lever in "neutral"...!

dump me, seems I have "over adjusted" the thing and did not remember I even touched it... cleaned and greased everything I could reach to and re-mounted the lever firmly. Will bleed the system tomorrow and see how far I get...

BTW: while dismantling everything from the right handlebar, I thought that there was a push-pull assembly for the original switch unit to have two cables, I think from a two stroke Japs bike (Kawa?). Exactly the ones we have on our bikes just with two cables for the Mikunis/Keihins. Anyone remember the type of bike they came off of?

thanks a lot
 
Later RGS types have provision for double pull throttle cables. You may have to tap out the second thread.
Also, I think, it was the GT750 Suzuki that had them too.
 
Grant said:
Later RGS types have provision for double pull throttle cables. You may have to tap out the second thread.
Also, I think, it was the GT750 Suzuki that had them too.
Click to expand...

Hi Grant, mine has a second hole that is closed. with "tap out" you mean: drill out, cut the thread, right? Is the material soft enough to cut it easy by hand with a thread-cutter? Tried it once on an aftermarket item, which broke...

thanks Grant and Brett for the info. I will check my options tomorrow. Maybe first try to drill the exisiting one and if that one fails, get one new as per the link above.

cheers
 
Lothar has your lever the little grub screw system for adjusting the freeplay? If so these are renowned for loosening themselves, best removed or at least Loctited. The modern type levers adjust span independent of freeplay.
 
I bought one of the ND twin cable jobbies from somewhere. Might be cheaper easier to buy one than modify and try to find a barrel. Maybe the GS models from Suzuki also use them?
 
"BTW: while dismantling everything from the right handlebar, I thought that there was a push-pull assembly for the original switch unit to have two cables, I think from a two stroke Japs bike (Kawa?). Exactly the ones we have on our bikes just with two cables for the Mikunis/Keihins. Anyone remember the type of bike they came off of?"

Suzuki Kettle GT750. GT Reiner has them in stock.
 
Tippie said:
Lothar has your lever the little grub screw system for adjusting the freeplay? If so these are renowned for loosening themselves, best removed or at least Loctited. The modern type levers adjust span independent of freeplay.
Click to expand...

yes, it does. the screw though is the "seat" for the little rod that presses the master piston in, so no chance in removing it. Loctide is the way then...
 
Piranha Brother 2 said:
I bought one of the ND twin cable jobbies from somewhere. Might be cheaper easier to buy one than modify and try to find a barrel. Maybe the GS models from Suzuki also use them?
Click to expand...

Not sure GS had the push-pull...? I had a GT200 myself years ago and do remember that aside of the kick-starter, the bike had the "dyna-Starter", basically an alternator used to start the engine. Why then do some of the switches not have a starter-button...?

see: https://www.ebay.de/itm/401468433238

that should be the one I should look for, but the price...  :-[

https://www.ebay.de/itm/273546873612?frcectupt=true
 
I think some of the smaller bikes like the GT 185 had kick-start only, so no need for the button in the switch assembly.

HTH
Gerald
 
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