ABS fixing knowledge / experience?

[Adam Ef]

Just wondering if anyone has any ABS knowledge on here. More specifically is it something to avoid if there's issues?
Got a chance to possibly get another VFR, but the ABS doesn't work and hasn't for the last few years. The owner has sought advice, but I get the impression he's not technically inclined as didn't really know about error codes or how to find them. So I don't think he's delved into it too much and has just lived with it not having ABS.
Beyond possibly having to replace sensors or pump "(which are readily available) how much worse could it be?
I'm not sure it's ever even been cleaned, so could be simple as brakes binding, master cyclinder jamming or possibly even a fuse? There was an advisory on an MOT form a couple of years ago that there's a slight fluctuation in the front brake when applied. Possibly a warped rotor? Could that cause issues?


ps. I know I should be asking this on a VFR forum...

[SV650rules]

All I know about ABS is that you have to be careful when bleeding the brakes, because if you get any air into ABS pump / control unit it is a big problem. There are solenoid valves in there to release / apply brake pressure to the wheel cylinders and I know on a car if you get air into these valves the brakes go spongy, which no amount of bleeding will cure - they have to plug in a computer with proper ( expensive) software to open the valves manually and dislodge the air and then re-bleed brakes.

Yes you do really need to go on VFR forum for specifics on Honda brakes.

The usual suspects on ABS are the pump and wheel sensors / wiring ( dirty or broken ) on most ABS the fault light will come on ( or on my AL7 never go off ) if the system doea not receive pulses it is expecting from the wheel rotation sensors. On my AL7 to get the ABS fault light to go off ( it comes on with ignition ) it has to see the bike wheels rotate ( probably at least one revolution of the wheel ) to check pulses.

The ECU / electronics on most bikes is the most relaible bit and the actual mechanical devices / sensors the most likely to give problems.

[Craig380]

Originally Posted by SV650rules

All I know about ABS is that you have to be careful when bleeding the brakes, because if you get any air into ABS pump / control unit it is a big problem. There are solenoid valves in there to release / apply brake pressure to the wheel cylinders and I know on a car if you get air into these valves the brakes go spongy, which no amount of bleeding will cure - they have to plug in a computer with proper ( expensive) software to open the valves manually and dislodge the air and then re-bleed brakes.

I haven't bled the brakes on my Gen 3 yet, but the factory manual doesn't give any special instructions or demand any special tools for the job, the process is the same as for a non-ABS bike.

Just got to make sure the reservoir doesn't get empty, I suppose ...

[SV650rules]

Originally Posted by Craig380

I haven't bled the brakes on my Gen 3 yet, but the factory manual doesn't give any special instructions or demand any special tools for the job, the process is the same as for a non-ABS bike.

Just got to make sure the reservoir doesn't get empty, I suppose ...

I have bled the brakes couple of times on my 2016 SV, using mityvac vacuum device, also done many cars with ABS using mityvac. As you rightly say and I mentioned in previous post, getting air into normal non ABS brakes is bad enough, but with ABS it is more of a problem as special equipment required to get it back out - as you say just do not let reservoir get empty, otherwise bleed just the same as non ABS. One of the most important things with brakes is to regularly flush fluid out, as it absorbs moisture and will cause corrosion inside the system if left in too long...

[embee]

A very common problem on bike ABS is if the pole wheel (toothed/slotted ring) gets bent, often from clumsy disc lock use or careless bike parking next to each other. The gap between pole wheel and sensor is usually of the order of 1mm (check exact model spec) so any bends/dinks will often result in a gap too big and the pick-up doesn't give a continuous output signal.
Fault code is your friend .....

[Adam Ef]

All good info. Thanks everyone.

[SV650rules]

Originally Posted by embee

A very common problem on bike ABS is if the pole wheel (toothed/slotted ring) gets bent, often from clumsy disc lock use or careless bike parking next to each other. The gap between pole wheel and sensor is usually of the order of 1mm (check exact model spec) so any bends/dinks will often result in a gap too big and the pick-up doesn't give a continuous output signal.
Fault code is your friend .....

Agree, the pulse wheel is pretty fragile on motorbikes and is vulnerable when wheel is taken in and out, the pulse on a car is often off a machined castellation on rear of hub, so much better protected and does not get disturbed by taking the road wheel off.

I suppose even a piece of road grit can damage the ABS pulse wheel, wiring or sensor on a bike