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Trying to fix a spongy Clarks M2 rear brake by bleeding it.
Calliper removed from bike, pads out and block of wood in caliper. Pistons fully retracted.
Connected empty syringe to lever end and full syringe to caliper.
Can't get full syringe plunger to go in, even when pulling the plunger out in the lever syringe.
Caliper syringe moved if brake lever is pulled in gently.
What am I doing wrong?
Why won't the lower syringe allow me to depress the plunger?
Help please....
Cant answer your question I'm afraid , had issues bleeding or trying to bleed my rear M2 caliper , the bleed grub screw rounded off with a good allen key ! .. had to replace with a set of deores till i get it sorted !
Hope u sort your issue out .. watching with interest
My first guess is that the lever piston is sticking, and blocking the port to the reservoir that normally allows fluid to pass through when the lever's released. If this is the case, it'll also prevent fluid from replenishing the system as the pads wear, causing a long lever travel.
That sounds plausible, any idea how to free up the piston?
Do you need the plunger in the lever syringe?
Take the plunger out and ust see if you can push fluid up in to the empty syringe.
Tried that and it still won't shift, even tried with a bleed cup in the caliper and no joy.
Following on from Coatsey's suggestion I'm going to try winding the lever as far out as it'll go with the travel adjuster and see if that helps
I sent a set of m4 back as came pulling to the lever and couldn’t get much better with a fresh bleed.
Freeing the piston will require stripping the lever down, usually involves removing the lever blade from the body/adjuster screw, and removing the circlip that holds the piston and it's return spring.If it's stuck, then removing the hose may give access to push it out from the rear.
Sounds like something at the lever is blocking the port not allowing fluid to flow.
Have you tried a top down bleed instead? Full syringe at the lever and pumping the lever to push fluid down to calliper.
I had this with a set of tecktro brakes. Even after stripping and rebuilding them I could not do it. I came to the conclusion the port was actually drilled in the wrong place as the piston never uncovered it
Did mine at weekend
I do old fashioned way.
Take reservoir top off. Take grub screw out of calliper. Keep filling res up to brim pull lever right in slowly, finger over calliper hole release lever slowly making sure oil is always briming in res. Repeat until no bubbles either end.
For me I have to see no air sucking down from top. It’s such a fine line.
I also first tend to pump pistons right out to clean and let any crap come out. Also tend to bleed with pistons a few mm out, so when done you can push them back and res will overflow. Bit messy but I do it off the bike.