XS400RJ Seca Front Caliper

[Mazzini113]

I'm in the process of bringing a Seca back from the dead, the engine is running great, minus a clutch cable stretched to death. However I'm having some problems with the front brake, and was wondering if anyone can give some advice. This piston cup is stuck, I bleed the brakes and pumped it out most of the way and still it's not wanting to break free. My concern is weather or not this caliper is lost cause, don't want to play with the devil on safety here. Does anyone know something I can do to pop that cup out without damaging the caliper housing? Pumping it out revealed fresh unrusted/pitted metal on the cup, so I do not believe there is any rust inside of the housing, but I would like to do a full inspection, I have read up, and seen a couple diffrent forms where people have used compressed air to pop the cup out? Has anyone had success with this in the past? For those of you that have rebuilt an XS400RJ caliper, how far did the cup pop out before coming all the way out? Was it almost to the brake bad retention bars facing the hub?

 

[16VGTIDave]

A grease gun is a better and safer option. You can build much more pressure with a grease gun to get the piston moving. But, you don't have to worry about shooting the piston across the garage at high velocity. Grease doesn't compress, so it won't store potential energy. Air compresses and stores energy. It has been few years since I last had to do this, but it isn't difficult to make a grease fitting that threads into the hose fitting. Just keep in mind that you need a metric banjo bolt - the stock one works fine, and a banjo fitting that you can install a grease fitting into.

 

[Jeff0133]

My piston was badly seized, soaked it with pb blaster and used compressed air on the bleeder, came out like nothin'.
But be careful when it gives...it comes out with a vengeance.
Best of luck

 

[BDxs400]

I rebuilt my caliper on my seca, and with low pressure CA I had no problem getting it out. I believe I had the air regulated to 60psi. I might even have a caliper laying around that I believe has been taken apart already. Ill look for it tonight if your interested. Im usually not one here everyday so reply might be awhile

 

[Mazzini113]

My piston was badly seized, soaked it with pb blaster and used compressed air on the bleeder, came out like nothin'.
But be careful when it gives...it comes out with a vengeance.
Best of luck

Thanks, I'll try and pop it out tonight, I left it soaking in PB after I had read your message, I'm hoping this eliminates any stickiness, this bike as an oddly large amount of calcium deposits on it all over everything, so my guess is there is some deposits down in the walls of the caliper that have seized it.

 

[16VGTIDave]

Calcium? More likely corrosion. A mild acid like vinegar will remove the corrosion, just be sure to rinse well with water then dry thoroughly.

Be sure to replace all the rubber parts on the caliper now that they have been exposed to oil.

 

[Jeff0133]

Yep,those caliper seals probably are vulcanized to the piston by now, if you reuse them you'll be facing leaks all over....