Rear caliper seized. What now?

[rd400canuck]

Just went to take the rear brake caliper apart to check its state and it seems to be seized. I took my air compressor with 90-100psi in it and used that and the cups wouldnt budge at all.

What are my choices?  Ebay or Econco?

[rodneya]

Put a grease nipple in place of the bleed screw, block the banjo fitting and use a grease gun to push out the pistons

[motodreams]

This has worked for me as well.  Try and make both pistons come fully out at the same time otherwise you will no longer be able to put pressure on remaining piston.

[m in sc]

2 things:



1: throw some heat at it. not ridiculous, but it will def help. plan on replacing the seals of course. 

2: clamp piston on fitting side in and blow 'inboard' piston out.  then, take clam-shells apart. use thin piece of aluminum (like flashing) and block 'crossover' hole in caliper body. reassemble caliper but with one half up, other down. un-clamp 'outboard' piston, then blow into fitting. 2nd piston out. ive never had an issue doing it this way.

[rd400canuck]

ok thanks for the advice guys. I'll have a go at it this weekend.

It's the last thing I needed to get sorted before I can put it all back together to iron out any bugs then take it to the shop for some tires and a safety so that I can insure it. Then it's good to go for Deals Gap 

John

[Striker1423]

ok thanks for the advice guys. I'll have a go at it this weekend.

It's the last thing I needed to get sorted before I can put it all back together to iron out any bugs then take it to the shop for some tires and a safety so that I can insure it. Then it's good to go for Deals Gap 

John

I cant wait! It'll be a first for me too!

[SUPERTUNE]

We've been dealing with stuck calipers for at least 20 years...Mark explained it well with removing one side at a time.
ANYTIME when using compressed air always wrap in heavy towels...
Chuck
Yes, I'm looking forward to Deals Gap and meeting you guys!

[m in sc]

I USUALLY AIM IT DOWN INTO A 2 OR 5 GALLON BUCKET FILLED WITH RAGS. sorry caps. yeah, they can be a missle.

[Dvsrd]

And that's why using a grease gun, or the master cylinder to push them out. Much safer than compressed air, and also gives much higher pressure, if required.

[m in sc]

never found the need. air will do it.

[SUPERTUNE]

If using a stock rear RD400 master cylinder you must take out the brake fluid supply line fitting out of the master cylinder and make sure the tiny hole is clean. There is 2 under there going into the piston bore.
That tiny hole will cause the brake caliper not to retract all the way, then drag and build heat, then seize.
Always use new pads and throw the anti-rattle shims in the trash and don't use them!
Check disk for runout anything over .015 in. is not good.
Tips of the day...

Chuck

[SUPERTUNE]

I should add this also...due to the OEM RD400 rebuild kit no longer available from Yamaha part # 1A1-20000-50-00
When needing to rebuild the RD400 rear master cylinder, use a OEM Yamaha FJ 1100-1200 kit but re-use the stock RD shaft and not the FJ shaft.
All your using is the rubber parts from this kit.
Yamaha Part # 2YK-W0042-50-00 about $50.
Chuck

[rd400canuck]

Awesome... thanks for all the input and knowledge as always 

Hopefully this weekend all is successful and I can get them out of the caliper. As far as the master I have gutted that as well... I dont know what was in there but it look like saw dust when I removed the oil feed line. I have rebuild kits for the caliper and master from Econo ready to be ordered. I just want to get a look at the cup surfaces once I get them out to make sure they are not pitted.

John

[Evans Ward]

A soak in Evaporust for a day or two with the caliper submerged wouldn't hurt either. Love that stuff!  I've done it both ways: my take- grease takes longer and is messier, air pressure nozzle from compressor is way faster and easier. Never had one that wouldn't come out with air. Stubborn ones will come out after 10-15 seconds or so. Rag on the projectile side. Good luck and whip that task!

[rd400canuck]

Alright guys.... I followed everyone's advice, went and bought a rubber tipped gun and they came out. They put up a fight though but they finally gave in. Thankfully the cups look fine... a little pitting towards the top but none of it near where the seals touch.

Now I need to ask... how the hell do I clean the track on the inside where the seal goes without scratching it up? It's full of old rubber bits that wont come off.