ZZR 600 front brake issue

[ronny86]

I'm posting on behalf of my friend, he's old so he doesn't have the Internet, he's pritty good with bikes so he knows a thing or two but he's have problems with his zzr front brake, he bought the bike a few weeks ago and the front brake was seized on, he got the stuck brake cylinders loose and the brakes work, but the handle goes all the way back to the handlebars and anyone in uk will know it won't pass it's mot like this, he's tried bleeding it many times and still won't harden up, so I said I would ask on here to see if any one has any ideas, cheers

[ronny86]

went to see me mate yesterday and he said if he fills master fluid and pumps front brake handle air comes out but the odd time the fluid will shoot out the mater cylinder and hits his garage roof, hes tried leaving it over night for air to pull through and endless amounts of time adding fluid pumping brakes etc but still nothing

[DonTZ125]

Grab the front hoses while pumping on the lever - do the hoses swell up? Not uncommon for older bikes, and that bulging takes a LOT of fluid / lever travel.

If that's the case, new braided lines are a quick, economical fix.

[ronny86]

i asked him to try it and but he said its not that :-/

he said if he clamps the right brake hose then the brakes work fine, soon as he takes the clamp off it stops working again, ive told him endless times to change the hose, they need doing anyway with being so old and least if it is the hose he hasnt waisted all that money on calipers

[DonTZ125]

Clamping the right hose - do you mean 'clamping off the hose such that no fluid travels to the right caliper'?

Well, in that case you know exactly WHERE the problem is, if not what. Replace the damn hoses, strip and clean the calipers (sounds like they could use it anyway, if they were seized), and sort the situation out! Anyone who 'knows bikes' but won't tear down a known-problem set of brakes needs a kick in the backside!

How worn are the pads? If the pistons are too far out, strange things can happen - there is so much fluid volume involved that the fluid itself starts to compress and the caliper start to flex. Get the pistons back in where they belong!

[ronny86]

do you mean 'clamping off the hose such that no fluid travels to the right caliper'? - yep, sorry

well for starters hes using a marster cylinder off a 400, hes stripped and cleaned the pistons and hes just put new pads in, im pretty sure the piston position is fine, ill take my laptop to his and show him this thread and if he still dont listen then he can go waste his money!

[DonTZ125]

well for starters hes using a marster cylinder off a 400

Ok - THAT's new info, and quite possibly the critical snippet!

I'll wager that mcyl is too small for the ZZR600 calipers. That's why it works great when you clamp off one hose - you've just eliminated half the fluid flow requirement! Your buddy needs something bigger - get a mcyl off a ZZR600, or an R6, or something like that