[Shubham Negi]

So i have a cbr250r abs 2013, 3 months ago while riding, suddenly my front brake lost nearly half of the pressure. The could pull the lever all the way through. I gave it to a trusted mechanic and he said he did something (didnt charged for it). And the issue went away. Now again the same problem happened again. The longer I ride, the more pressure i lose.
Front tire was also running tight so i got the pistons cleaned up and and tire was rotating freely again. Then he said he removed some air from the system and the brake became perfect again. He said if it happened again, master cylinder will need a rebuild or replacement. Can you guys enlighten me what might be the cause, if its master cylinder culprit or anything else.

Also, can a NON-ABS rebuild kit work in ABS master cylinder? I couldnt find a rebuild kit for specifically ABS model.
Thank you in advance.

 

[Shubham Negi]

Thanks man, I'll just get the whole assembly then.

 

[Shubham Negi]

Im from India so shipping is gonna cost me more than the product itself
I can get hold of the whole assembly for around 2500 rupees (25 -30 USD). But thanks for the suggestion brother.

 

[Shubham Negi]

Thanks for replying, actually the roads are not that bad as you're saying and I have been riding since 2018 and this issue occured just now. No offroading done.
Also no leakage of brake fluid at all. I guess master cylinder is the main culprit.

 

[Shubham Negi]

YES
Sometimes a few activations, pumps, of the brake lever will restore the pressure, but as you apply force on the lever the pressure drops again. Of course you shouldn't drive like that.
In most cases, the cylinder, the bore, was not damaged, and the complete piston kit is replaced, or only the two seals of the piston.

To remove the CIRCLIP (90651-MA5-671) that holds the piston, you need a special tool (with a narrow and long nose): Internal Snap Ring Plier

That is exactly whats happening. Pumping restores it temporarily but it loses pressure as soon as i brake for real. I will change the cylinder as soon as i can find it. Thanks

 

[Shubham Negi]

Thank you so brother for your input, i really do appreciate your effort. Can't be more happy to receive such a support.
.
Update :- removed the abs fuse. (abs not working now) ran the bike around 30kms the brake isn't losing pressure anymore.
What can be the probable issue in abs?
Can abs be repaired?
Or do i have to look for new abs unit ?

Is your brake working fine now after removing the fuse?? Replacing the master cylinder didn't solved the issue on mine as well.