ABS - help needed

[The Gecko_imp]

I know there is quite a bit of insight scattered over many posts, but it is hard to apply this knowledge to my (recent) problem. Any help would be really welcome. Here is what happens on my m/c:

- turn ignition on : ABS light on as expected
- start engine and roll : light goes off, as expected
- riding : no issues
However, when you brake hard enough with the rear brake the wheel blocks and the ABS light comes on and stays on until you turn the ignition off,
- I have not tried with the front brakes.

This seems to indicate that the valve inside the ABS unit (which is supposed to release the pressure and open up the brake momentarily) does not operate when needed BUT the unit cannot tell when the self test is run at start. Would you have any idea what could be wrong ? or what I can do before taking her to the dealer and spend a fortune ?
Thanks !!

[Lord Popgun]

I just got back from a trip and am just too tired to delve into this in detail.

However, First check the speed sensor gaps on both wheels for proper spacing and that the rings are not bent or damaged. Make sure there are no bugs, dirt, etc. stuck in the sensor gap or any of the slots.

Also the book says DO NOT remove any ABS connectors with power applied. Make sure the ignition is off.

[max]

Gecko we would like some more info;

Did the wheel lock up and stayed locked?

Did the situation clear itself?

And the last time the fluid in the system was replaced?

Reading on the web it occurs to me that abs may pose more problems at the wrong time than the advantages it has if left to "fend for itself" as time passes and parts start to corrode due to lack of use.

Here is one of the better diagrams on the workings of the system;



And a picture of how these units look nowadays;



My only bike with abs is the cb1000r and i test both brakes regularly on a flat grassy surface at slow speed, i also have a special bleed nipple which has an adjustable outflow and i use this to expel enough new fluid to replace the pump body's internal old fluid which mixes downstream with the new fluid when the abs is made to operate.
After the excersize i replace the fluid again to make sure it has exited the system.

All this would have made better and more reliable if there was an abs cycle built into the system from the factory to replace the fluid inside the modulator body.

The abs selfcheck includes a continuity test for all solenoids and the pump to ensure all parts are not open circuit and the sensors are working properly when the vehicle starts to move above a set speed.

But these tests do not include if the parts are stuck and the user is unaware of this until.......!

[The Gecko_imp]

@max, to your questions:
1) rear wheel locked up briefly, back turning again when I released the rear brake pedal - but abs definitely didn’t kick in,
2) problem remains (as described before), comes back next day with the same symptoms,
3) I replaced all fluids 2 months ago, but didn’t know how to make sure the fluid in the abs unit gets flushed, chances are some of the fluid got flushed, and some is as old as from 2017.
Thanks for the diagram !

[Gone in 60]

Hmmm, one of my BMWs did this. It turned out to be an internal pressure sensor inside the ABS unit, and not something that was serviceable without replacing the ABS unit itself.

Hope your problem is more easily resolved.

[The Gecko_imp]

Thanks for the hint anyway, Gi60 !

I just got back from a trip and am just too tired to delve into this in detail.

However, First check the speed sensor gaps on both wheels for proper spacing and that the rings are not bent or damaged. Make sure there are no bugs, dirt, etc. stuck in the sensor gap or any of the slots.

Also the book says DO NOT remove any ABS connectors with power applied. Make sure the ignition is off.

Thanks LP, I don't see any dirt on the sensors and spacing looks good. Also wonder whether such causes wouldn't be detected during the self-test after turning the engine on and rolling. Any thoughts ?

[max]

Gecko thanks for the answers and flushing the fluid so recently, this helps to pinpoint the repair;

The thing i would do is find a large enough grassy or similar area and gently operate ( excersize ) both brakes ( to operate and feel the abs pulse ) and see if you can un-seize the valve in question, doing this repeatedly could just restore the functionality and make things work as they should.

The valves have spring loaded solinoids, these are coils which have moveable soft steel cores ( pintles ) which move from their rest position when the coil is switched on and the resulting magnetic force pulls the pintels from the seat , open the valve and allow fluid to flow, much like fuel injectors or the water valve in a washing machine;


And with repetitive activation of the coil the pintle may just free itself and return to normal operation.

Definitely worth a try

[Lord Popgun]

Thanks for the hint anyway, Gi60 !

I just got back from a trip and am just too tired to delve into this in detail.

However, First check the speed sensor gaps on both wheels for proper spacing and that the rings are not bent or damaged. Make sure there are no bugs, dirt, etc. stuck in the sensor gap or any of the slots.

Also the book says DO NOT remove any ABS connectors with power applied. Make sure the ignition is off.

Thanks LP, I don't see any dirt on the sensors and spacing looks good. Also wonder whether such causes wouldn't be detected during the self-test after turning the engine on and rolling. Any thoughts ?

Thanks LP, I don't see any dirt on the sensors and spacing looks good. Also wonder whether such causes wouldn't be detected during the self-test after turning the engine on and rolling. Any thoughts ?
I would think it would be detected and set the light or cause it to flash. But we had a user with a weird ABS problem that was caused by a bent rear ring.

I threw those out as they are fast and easy to check before getting into it. A quick glance at the book this morning said to jumper the ABS diag. plug and see the actual code. And I was hoping Max would get into that.

[The Gecko_imp]

@max, would you agree with another post/er some time ago, saying that (if anything else fails) flushing the fluid AND exercising (as you suggest) AND do both a few more times is worth a try too ?
@LP thanks a lot for the clarification

@anybody owning a service manual for the 2017EX : could you contact me by PM, please !! Not asking for anything illegal, just need to know if the ABS system is covered in greater detail than in the older manual which I have.

[peterbaron]

2 PM sent