SOHC.co.uk Forums > CB650

front brakes

(1/2) > >>

pae:
Hi folks, long toime since I posted, but I'm doing some work on judodave's 650z and wonder if anyone can help.

We're having an almighty problem getting the front brakes lever to go firm, but I'm stumped to know what else to try. I seem to recall my previous 650 never had a very firm lever, but can't say if it was like thi one or better.

Anyway, the bike's got new pads, new pistons and seals in both calipers, new master cylinder seal kit, a new 'o' ring around the base of the plastic master cylinder reservoir. Just about everything, except the hoses are new.

I've tried bleeding with a syringe by sucking fluid through from the reservoir down and out the bleed nipples, and also by pumping fluid the other way (into nipple until it comes out of reervoir). I've also done the traditional undo nipple-piull lever-do up nipple-release lever etc way. None of them make it any better which makes me think I've got the best I can expect.

I can get the wheel to brake hard when pushing the bike along using about 1/2 - 3/4 lever travel and it feels firm, but the lever never goes solid. With more pressure you can always squeeze the lever harder which seems wrong, even though the brake performance might be OK.

I recall my previous one was a bit like that, but that was few years ago. Does that sound 'normal'. I've got an MOT booked in the week.

Anything else these 650's are known for in the braking department that I should check?

thanks, Phil

andy120t:
I don't know specific 650 brake characteristics but old hoses - (rubber ones) - will contribute to any sponginess.  As they age they expand more under braking pressure and do the feel gets worse. Key thing is that the lever doesn't come all the way back to the bars.

Braided lines may not fit the look of an older bike but will help - my breaker sells 2nd hand ones for a tenner a go which helps keep the cost down. That way you'll have eliminated everything - meaning any remaining lack of performance is down to the brakes themselves!

Bryanj:
Depends on your tester, when i did it as long as there was some "reserve" travel when the wheel locked it was OK bt me

pae:
Thanks chaps, I'm dropping the bike off a couple of days before the test, so I'll ask him if it's worth putting it through the test then.

Phil

K2-K6:
Some of this era i.e. earlier twin disc set-ups had a distinctly long spongy travel but they should never touch the bars though.

It's just as much to do with the master cylinder ratio compared to the piston size that dictates travel at the bar if no air is present.

If you had a master fitment for a single caliper wrongly fitted you'd get roughly twice the lever movement.

I've had some systems that we cold only get to bleed all of the air out by lifting the caliper above the mastercylinder and putting a block in place of the disc to allow a conventional bleed by pumping fluid through to take place as the air rises it is expelled more easily.

Navigation

[0] Message Index

[#] Next page