Front brake drag z900a4 twin disc

[markhemstock]

Refurbished my 5/8 master cylinder replaced all brake lines with new ones ( rubber and steel bottom ones) replaced caliper seals and dust covers one new piston due to slight corrosion and new pads. Bled the system but got a lot of brake drag. Any body had this problem have much drag should there be wheel stops dead if you try spinning it. Been at it all week still unable to solve help much appreciated cheers mark

[z1bman]

have you lubricated seals & the bolts that the calliper slides on with rubber grease? is it just one calliper sticking? are the calliper mounting brackets square to the disc?

[PAULJAC47]

Have you got single or double discs? there is a thickness difference between the pads for the single disc caliper and the double.Check out what new pads you have,been there t shirt etc..Paul J

[Chris Riv]

Did you make sure the tiny return hole is clear in the master cyl bore? If its blocked by corrosion or dirt, the fluid cant return to the cylinder properly. Try pumping the brake hard, then with the lever not compressed, slacken a bleed nipple to see if fluid comes out the the wheel spins ok. If it does, you know fluid pressure is making it drag. If not, then its a mechanical issue.

[markhemstock]

Thanks for help got problem down to fluid pressure. Released bleed nipples and wheel frees up. Pumped up pressure so brake was binding then released banjo bolt at master cylinder so no blockage or problem from there down to calipers. Stripped master cylinder down again to make sure all ports clear as Chris riv said. Took off fluid reservoir to do full check and the master cylinder only has one port drilled and one half drilled that's not through to master chamber. Looking at all diagrams I have should have two ports any body out there give me any more info please. It's a twin disc a4 and 5/8 master cylinder proper confused now!!!

[johny brando]

Thanks for help got problem down to fluid pressure. Released bleed nipples and wheel frees up. Pumped up pressure so brake was binding then released banjo bolt at master cylinder so no blockage or problem from there down to calipers. Stripped master cylinder down again to make sure all ports clear as Chris riv said. Took off fluid reservoir to do full check and the master cylinder only has one port drilled and one half drilled that's not through to master chamber. Looking at all diagrams I have should have two ports any body out there give me any more info please. It's a twin disc a4 and 5/8 master cylinder proper confused now!!!

Chris Riv is 'On the money' ....thats likely the problem. On a Kawa 900 you do have 2 holes inside the M/Cylinder ..... one is the Piston filling hole (=upstream hole )the vent hole on the (=down stream side ) of Master Cylinder piston & it sounds like it is this one thats blocked. It's a very tiny "pin head sized drilling" located on the base/floor of the master cylinder resorvoir & drops down into the pressured side of the master cylinder piston...it's function is bleed/release the internal line pressure back into the main resorvoir when the brake lever is released. Compressed air will be the best means to clear it ....next best= Contact cleaner spray.
If it's not that ( & thats unlikely ) I'd then check you Caliper pistons & seals are not cruded up i.e. good condition ,clean and free in movement .
Cheers Johny B

[markhemstock]

Thanks Johnny B. All new seals and pistons in calipers. Trying to post a photo of master cylinder to show but not having any look. As you look at master cylinder base from above ( lever side on right as if it was on bike) with reservoir removed there are two drillings in the base of the master cylinder. The one at brake lever side is about 2 /3mm in diameter and goes though to the master cylinder chamber and is clear. About 1cm to the left (banjo bolt side) is another drilling of the same diameter but is probably only drilled 3/4 of the way through. Tried cleaning it with spray and pin shinny alloy at bottom no hole. Only sign of one drill hole when you look down cylinder chamber. On the casting underneath is stamped 5/8 TOKICO JAPAN. Is this a z900 a4 cylinder. This is the original cylinder that was on bike when I had it over 15 years ago and the brake was ok prior to not using bike for about 7 years. Once again thanks for everyone's help keep it coming cheers mark

[Chris Riv]

Hello again, the "half drilled hole" should have a very tiny bleed hole at the bottom. With the cylinder stripped, you should be able to poke a piece of wire (a single bristle from a wire brush is mt favourite) to clear it. When done, make sure no burr or debris left where the tiny hole enters the bore.

Cheers, Chris

[johny brando]

Thanks Johnny B. All new seals and pistons in calipers. Trying to post a photo of master cylinder to show but not having any look. As you look at master cylinder base from above ( lever side on right as if it was on bike) with reservoir removed there are two drillings in the base of the master cylinder. The one at brake lever side is about 2 /3mm in diameter and goes though to the master cylinder chamber and is clear. About 1cm to the left (banjo bolt side) is another drilling of the same diameter but is probably only drilled 3/4 of the way through. Tried cleaning it with spray and pin shinny alloy at bottom no hole. Only sign of one drill hole when you look down cylinder chamber. On the casting underneath is stamped 5/8 TOKICO JAPAN. Is this a z900 a4 cylinder. This is the original cylinder that was on bike when I had it over 15 years ago and the brake was ok prior to not using bike for about 7 years. Once again thanks for everyone's help keep it coming cheers mark

Mark ......ditto what Chris say's below , it's a tiny tiny hole & it's smack bang in middle of the bottom of the that left hand hole...the one on the Banjo side of the chamber ! it's really TINY a PINHEAD size ..it's there mate, it's just playing games with you, Haha . Try using a Magnifiying glass maybe ...I'm being serious ?? Cheers, Johny B

[markhemstock]

Many many thanks to you all and of course you were all right. When you said tiny Chris I now know what you mean should have gone to spec savers!!. Great club with web site to pick people's brains when your in trouble once again thanks a lot cheers all mark