Hi guys

The front brake lever on my K100RS is acting a bit strange................. 


The lever is really stiff to operate and it also has some free 'play' after application. The brake light does not come on unless I move the lever back to where it should be, no more that 1-2mm

The bike has a new master cylinder, lines bled, all seems OK

Its really strange - it just started after I adjusted the front handlebars slightly upwards. I moved them back to the original position in case this was the cause but no luck

any advice would be greatly appreciated

cheers
gary

G'day Gary, I don't follow your post, does the light stay on until you move the lever back that extra 1 or 2 mm or is it the way you said it with the light on when moved back? The light should only work when you squeeze the lever to operate the brakes. With regard to the stiffness of application, is it possible the pads are stiff and the bleeding of the master cylinder has transferred the feel back to the lever?
Perhaps just checking the switch at the lever will show the light switch needs a tweak maybe outwards.

Check the pivot is not worn and oval and also the surface where the plunger contacts the lever will wear and cause a very stiff point where the lever will not move till it gets pulled hard then as soon as it moves the brakes apply a bit harder than needed. I had it happen and a new lever was the answer.

Thanks guys

Sorry if the post didn't make much sense I was typing at 2am here in Australia

What was happening was the front brake lever, when pressure was applied, was very stiff in its action; very difficult to move back towards the handlebar. Would not move more that 5-8 mm After applying this pressure, the brake lever would not fully return to the stop; this was causing the brake light to remain on. If I pushed the lever back to the stop the brake light would go out. 

With the help of my son (who is a mechanic) this morning we bled the front brakes; he could not find any air in the system. After this,the lever is a bit 'spongy' but it retracts and the brake light works correctly. Short test ride  - brakes working OK. So I will leave it like that for a while and see how it goes.

cheers Gary

To firm up the lever, use an elastic to squeeze the brake handle towards the grip. Turn the handlebars to the left and leave overnight. This will expel any trapped air in the hydraulics.

probably a blocked equalizer tube inside the reservoir viper ....

there are two tubes in there ...one for the pump refill action and the other for the relief to let fluid back slightly to the reservoir and let the piston return to fully retracted ....else it gets stuck part the way out with vacuum effect .

thanks guys


Charlie - do I dissemble the Master cylinder to free up the plungers?

( sorry if this is a really dumb question.............)

hi mate they are visible from the bottom of the reservoir but you might find that the plastic of the reservoir will limit access

think I have a pic around here somewhere



possibly you could get a syringe and suck out the fluids  then probe the holes carefully ...flushing with fresh fluid

from what ive seen the fluid can get crudy and crusty  and just needs to be moved around and flushed carefully

hope that helps

While you have the reservoir off there is an o-ring on the base where it mates with the top of the master cylinder. Worth replacing this while you're in there.
Part No. 32721242624
or take the old one into a bearing shop would probably be the cheapest and easiest.
Cheers

thanks guys 

Still not right - bled the brakes etc etc no change.

It seems likely that its the blocked equalizer - might have got some crud in there. The PO replaced the master cylinder not long ago I will give them a clean out and see what happens


cheers
Gary

charlie99 wrote:probably a blocked equalizer tube inside the reservoir viper ....

there are two tubes in there ...one for the pump refill action and the other for the relief to let fluid back slightly to the reservoir and let the piston return to fully retracted ....else it gets stuck part the way out with vacuum effect .

Hi I'm a Newbie to the forum & your reply above is absolutely accurate & bang on with good explanation too ...normally when the down stream vent hole is blocked or partially blocked in the master cylinder it commonly causes the brake pads to drag & cook the caliper internals as you clearly & rightly stated with the vacuum that occurs. Is this actually occurring  in this case ? as it should be if that vent drilling is obscured in any way ? PS to the owner of the said bike ...Use compressed air to clean that vent hole NOT a piece of wire or secondary damage could occur.      All the best.