Bleedin' Bleeping Front Grimeca Caliper?

[comanche91]

Am putting this in the general Tech forum since so many MZ models use the same caliper as my 95 Silver Star. I've tried every brake bleeding procedure I know, and they all work - for a little while. Nice firm brakes, until I go about a mile. The more I use them, the spongier they get. Pretty soon I have to pump the front brake lever a couple of times to get pressure. It just will not stay firm for any length of time. Not good, it's making me nervous. Things I have done: replace fluid; "gravity" bleed overnight, conventional bleed using clear hose off the bleed screw into a jar filled w. fluid until all the air bubbles disappear, clean up reservoir and gasket, etc. No loss of fluid, no leaks anywhere, brake hose is new, pads are new. What's the best way to bleed this bloody thing? Or just junk the Grimeca junk and look for a Brembo replacement? Thanks, -Don

[Nozz]

Doesn't sound good. If it's not performing correctly, but not leaking at the caliper, it sounds like the master cylinder may be the source of the trouble. These must be used on a lot of other bikes, as I have gotten pads at the BMW store. No brakes is a showstopper! Have you replaced all the fluid?

[comanche91]

Doesn't sound good. If it's not performing correctly, but not leaking at the caliper, it sounds like the master cylinder may be the source of the trouble. These must be used on a lot of other bikes, as I have gotten pads at the BMW store. No brakes is a showstopper! Have you replaced all the fluid?

I suspect the master/reservoir too Nozz. The bike has been like this since day one. And yes, have replaced all the fluid. I've rebuilt several auto master cylinders, but not one of these. And have no idea if a rebuild kit is still available either.

[Nozz]

I'd just guess that since the front pads match some BMW, perhaps the MC kit would too. Good luck! There's always Grahams in England, right?

[MZCountryRider]

Here's one source I found for Grimeca rebuild bits: http://www.roadandrace.com.au/cat17.htm , there are surely others. You might check with Herdan Corp. in Port Clinton, PA http://www.herdan.com and Vintage Brake http://www.vintagebrake.com/ as well.

[comanche91]

Thanks for the links. It might just be the procedure I use, although it has always worked on other bikes. Fill the master, squeeze the brake lever, crack the caliper bleed screw w. a clear hose connected and immersed in a jar w. clean fluid, watch the air bubbles exit, close the bleed screw, and repeat until no more air. This always results in a nice firm lever, then after a mile or so I have to start double pumping the lever again for the front brakes.

I have a MZ ETZ 251 Maintenance Manual that says for these bikes to use a long hose and funnel hooked to the caliper bleed screw, pop the master top, crack the bleed screw, then elevate the funnel above the master and slowly pour brake fluid down the hose until the master is filled from the bottom up, then close the bleed screw. Tried that and the brake fuid didn't flow. Must need a longer hose.

[Skorpion]

comanche 91

One way that has been known to work on the ETZ,
If you fill and bleed the brakes and you find as in your case a spongy feel to the lever,
fit a rubber band around the twist grip and brake lever so as to keep a slight pressure on the brake and leave overnight,
all being well should be OK in the morning.

[DAVID THOMPSON]

i force it from the bottom with a pump

its been setting and not used after a fresh bleed
for several months its spongie feeling but puts brake on well
had to replace line after higher handlebars installed
dave
bike = 1995 Saxon Tour

[jimc]

Your bleeding procedure is basically correct.
I am not a fan of reverse bleeding or the vacuum bleeders.
Use clear hose. have a loop above the bleeder
close the bleeder before releasing the lever.
Watch for air bubbles or fizz when you re-bleed.
do not use a lot of force , rapid pumping, or release the lever fast, as this can entrain air.
Assuming you get good pressure after bleeding, try holding the lever HARD for awhile.
A sinking lever indicates a leak or more likely bad M/C seals. (does the fluid level go down?)
The funnel procedure seems nuts to me since an open bleeder thread is NOT air tight.
Good luck.
Jim

[comanche91]

comanche 91

One way that has been known to work on the ETZ,
If you fill and bleed the brakes and you find as in your case a spongy feel to the lever,
fit a rubber band around the twist grip and brake lever so as to keep a slight pressure on the brake and leave overnight, all being well should be OK in the morning.

You must be reading my mind or I'm reading yours - I'm doing that right now.

Your bleeding procedure is basically correct. I am not a fan of reverse bleeding or the vacuum bleeders. Use clear hose. have a loop above the bleeder close the bleeder before releasing the lever. Watch for air bubbles or fizz when you re-bleed. do not use a lot of force , rapid pumping, or release the lever fast, as this can entrain air. Assuming you get good pressure after bleeding, try holding the lever HARD for awhile. A sinking lever indicates a leak or more likely bad M/C seals. (does the fluid level go down?) The funnel procedure seems nuts to me since an open bleeder thread is NOT air tight. Good luck. Jim

No, I do not lose any brake fluid or ever have to add any. I use clear hose. The Silver Star has the screw-on top plate for the master, not the threaded cap. So when pumping w. the bleeder screw cracked, I have to do it very gently or brake fluid shoots up from the bottom reservoir hole about a foot.

[comanche91]

Just to be sure - the Grimeca master cylinders used on the MZ-500 models is piston size 11mm, correct? Thanks

[comanche91]

Got this one fixed too. I found a used stock Grimeca caliper, swapped them out, bled the brakes and voilà - good firm front brake now w. zero fade. I guess this means I need to find a rebuild kit for the original caliper. Since it wasn't leaking, does anyone know what to look for to repair it? Also, is there a source for a rebuild kit?

[Nesim]

Hi comanche91,
I understand that you got a new front brake caliper. So you may need to sell old one.
If yes, I need a front caliper for my Baghira. My bleeding screw doesn't stays in its place anymore. It bleeds oil whenever I push the brake. Other parts are ok.

Ready to make payment with paypal, and shipment will be to Turkey.

If I got it wrong, sorry from now.

Thanks

[comanche91]

Hi comanche91,
I understand that you got a new front brake caliper. So you may need to sell old one.
If yes, I need a front caliper for my Baghira. My bleeding screw doesn't stays in its place anymore. It bleeds oil whenever I push the brake. Other parts are ok.

Ready to make payment with paypal, and shipment will be to Turkey. If I got it wrong, sorry from now. Thanks

Hi Nesim. I have no problem with that, but I'm not sure the Baghira caliper is the same as used on the MZ 500 models. The MZ part number for the one I have is 94-67.696. Maybe someone on the forum can tell us?

[Nesim]

Hi Nesim. I have no problem with that, but I'm not sure the Baghira caliper is the same as used on the MZ 500 models. The MZ part number for the one I have is 94-67.696. Maybe someone on the forum can tell us?

THank you for your reply. You're right about that, part numbers are not the same. Mine is 9014243000. I did'nt realize that your bile is a MZ 500 model. I just saw the Grimeca name, lol.

Sorry for late reply. I have exams these days.
Thanks again.