(07-26-2021, 01:51 AM)Dave_imp Wrote: There is likely still some old fluid inside the abs module, unless it actuates multiple times it just sits there and gets old.
Hi Max. Excellent advice, as usual. If old fluid just sits in the ABS module unless it is activated, what is the best way to change the brake fluid to make sure all the old fluid is completely removed? I would like to ask a question about the CB1100 ABS system because I know how wise you are, and you always provide excellent explanations: If the ABS senses the front wheel locking and activates, is the ABS function automatically activated for the rear wheel. or does the ABS system independently sense and activate each wheel? Maybe one of your technical explanations? Thank you Max.
Hi Dave, The abs modulator ( the aluminium block with the brake lines ) is always switched on when the ignition key is switched on, the modulator pump does not cycle as far as i know at that point, it just starts looking at the front and rear wheel sensors ( the abs light illuminates ), as soon as the ( both ) wheels start to rotate to a certain speed the abs modulator sees both sensors operating normally and at a set speed it decides the system is normal, the checks are complete and the abs light goes out.
Each wheel has it's own set of solenoids ( 3 control valves ) and compression chambers ( 1 ) but one combined fluid pump inside the abs modulator housing.
In order for the abs modulator to operate ( pulse ) the brake light switch has to be activated ( even if the brake light is defect ) according to the diagram which shows the combined front and rear brake light wire connected to the abs modulator ( so it knows when to be active ) and one of the wheels to loose enough speed to reach a programmed setpoint ( not necessarily stop ), at that point the abs modulator blocks the brake lever line, releases enough fluid pressure to re-gain enough rotation speed of the wheel inside the spring-loaded buffer chamber inside the abs modulator, open the handlebar line again and pump fluid into the line ( with the abs pump ) to assist operation ( because it has released a small volume of fluid to release the brake ).
This operation continues until the wheel comes to a stop or the brake lever is released.
So the pulsing that is felt in the handlebars when the abs system is functioning is this constant brake and release to allow the wheel to maintain the best possible contact with the riding surface.
To replace the stationary fluid inside the modulator the abs system would need to be operated at convenient intervals ( don't know how much ) or some of it let out in a controlled way through a nipple with a very small adjustable opening where the abs pulses and enough fluid escapes through the valve in a small container to establish how much is expelled .
I'm working on such a valve but have yet to try this out.
However there seems to be no or little need to do this normally, there is little info available on this subject and i welcome more opinions about this, this is just my personal interpretation on the workings of the abs system, so i can be wrong with this.
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