(07-31-2021, 04:53 PM)Roger the shrubber_imp Wrote: [ -> ]The problem was likely related to the long term storage of the bike at my warehouse, inactive for about two years. Luckily, manipulation of the brake levers and vacuum bleeding the system restored function.
Bleeding the brakes by activating the ABS pump and energizing the solenoids is nothing new to me as an auto technician, and I have diagnostic platforms and software to perform the power bleed on modern car and truck ABS systems. Unfortunately, it's not as easy on most motorcycles as there really isn't a widespread standardized communication protocol and the data connectors and cables are proprietary.
My Triumph Bonneville T120 is an exception. It has a multi pin DLC which I can plug an OBD2 Bluetooth adapter into and pair it with my android phone running a TuneEcu app. This allows me to retrieve and clear fault codes, reset the maintenance indicator "wrench" symbol on the clocks, synchronize the throttle bodies, and perform a power bleed of the ABS system.
I wish this was available for my CB1100. Purchasing the factory service tools, software and diagnostic platform is cost prohibitive to say the least.
Interesting. I got my CB1100 back on the road after storing it in my garage for about 3 years. A few times early on I was a little startled when I would squeeze the front brake lever, feel a lot of resistance but get NO front brake actuation. It only happened about 3 times sporadically on the first few rides.
I had that happen sporadically on a Chrysler and it turned out the master cylinder had debris inside (corrosion). I strongly recommend you don't waste much time inspecting/servicing the brake system.
(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.
Thank you Max! This is a great explanation; well written. I am sure many people who visit this forum will gain from it, as I have.
Very well written, Max. That reminds me of replacing the brake fluid in my BMWs. I had a GS911 tool that replicated dealer service functions, which connected to the bike's diagnostic port. During a brake fluid change, it allowed you to cycle the ABS pump to expell old fluid and release any trapped air. I wonder if there's a similar tool availalbe for Hondas, or if the dealer can perform this function during a brake fluid change.
Thanks guys, this is just what i pieced together in my head from what i have seen done to these modulators, for some reason i have taken an interest in engine fault finding.
Gone i have seen this procedure on the bmw's done and it seems the thing to do, ironically they also seem to have the highest failure rate ( mostly from worn out electric hydraulic pump motors ) from what i can gather, no such procedure is available for most abs motorcycles or cars for that matter that i am aware of but it highlights the need to maintain the fluid especially on bikes with an abs system to protect the modulator from internal corrosive buildup as mentioned before.
and yes, i have measured the moisture content in the fluid from the calipers only ( by compressing the pistons after cleaning them and emptying the calipers ) and the content was just as high as in the reservoir, so it works it's way through the system
My feeling is that the manufacturers rely on the abs system to operate from time to time to exercise the modulator and keep things operational, apart from our two documented cases i have not heard of any others so there does not seem to be a pandemic of failing abs systems happening, if this was the case there would be a lot of recalls.
It is a bit of a long video ( 1,5 hrs ) but Martin from Zams channel in Germany explains and takes apart an abs modulator, it is from a cb1000 which has been standing idle for 6 years according to his description, i learned a lot from this guy and have just enough of a grip on the German language so i can follow what he is saying
;
https://www.youtube.com/watch?v=XIDuxA2cJiM
Ha! Yeah, Max, I got pretty good at disassembling and rebuilding the pump motors on BMW ABS modules. Shoulda made a business out of it.