Rear Brake Problems ABS

[ikewhite]

Son has a 1989 K100rs w/ ABS. After installing a new balance shaft in the engine, Test ride is in order. Engine off bike on center stand rear brake works fine, ride the bike down the road no rear brake, pedal is hard and will not stop. Of course I let my son be the first to ride his own bike. Some dealers say that it could be a wheel sensor, others say it maybe the ABS Modular that has to be cleaned and flushed with new fluid. Yes it has been a while for a brake fluid change. Any help will be greatly appreciated. Finally nice in Ohio have to get out and ride.
Thanks anyone

[CustomSarge]

I'd pump/bleed/replace the DOT4 with fresh & beat Hell out of the pedal on the centerstand. I'd be Trying to make either the master or caliper stick.

Granting one will: pop the plastic cover on the caliper & pull the caliper mount bolts for better access for a big screwdriver to carefully leverage the pads apart to "cycle" the system.

Pump the pedal until the pads grab the rotor, then (given it doesn't release) use the screwdriver to push the caliper (& master) back, this is a "cycle". Cycle the system until it clears OR you are confident it won't (10-20 for me). That it won't clear means changing one end or the other for a separating perspective. I've usually had masters' go bad, but recently I had one that was the caliper.

Bottom line (IMHO as always): ABS is a modulator exerting small +/- pressure differentials around the basic brake force exerted by the pedal. If you don't have basic brakes, ABS isn't the problem. Good Hunting <<<)))

[wndsrfr]

My '92 K75RT had exactly the same behavior on the rear brake--push down on the pedal & get no braking effort---lots more pushing sometimes yielded a lockup on the rear brake, sometimes not. Interesting thing, the rear brake modulator also heated up hot to the touch, so look for that the next time you try it out.

When I disconnected the ABS brain, I had fine braking action on the rear. That told me that it wasn't anything to do with fluid or master cylinder or caliper--it was clearly the ABS that was misbehaving.

I did numerous resets and code downloads trying to track down the problem --it would give the code for rear modulator, so I replaced that with one of two that I got from BeemerBoneyard (Thanks Mike!). Still had the problem, and then got codes for bad control unit. Went through the entire system with coaching from Brian Curry and Mick--thanks guys. So now, the control unit is off to "Module Master" (Gavin Curtis) to see if he can rebuild it.

I'm perfectly happy riding the bike without the ABS unit functioning--great braking action and since it's the first ABS bike I've ever had, I'm not dependent on it. Still and all, I want it working, so am sinking the cost of the control unit rebuild into one last try....

So, if your rear modulator is heating up, it's probably a bad control unit. I'll post a note when I get mine back from Gavin & let all know if it solves the problem.

Good luck!

[sztxk75sz]

How do I contact the module master???? Thanks....

[wndsrfr]

Here's the URL for Module Master.....mind you I'm not pushing their service since I don't have mine back yet----your bike should be just fine to ride without the ABS brain connected if you want to wait & see....

http://www.modulemaster.com/index.html

Regards,
John