Topic: Help finding front brake part .. and a story on how not to rebuild front brakes

[rob]

Hi everyone,

I was in the midst of rebuilding the right side front brake caliper, and in my haste I put the piston in backwards, with the flat part facing out, and subsequently it is stuck in the calper housing 

I took it to a service station, and tried to use the air compressor to pump it out (the same method I got it out in the first place), but no luck.  Does anyone think its possible to get out?  Its stuck in there pretty good, and the piston has a little lip that is below the square O-ring.

So, does anyone know if I can buy half the caliper housing, piston and O-ring? Or have a part number for it?  Or do I need to get a whole new caliper?

Not my finest moment...

Rob

[Terry in Australia]

Don't sweat it Rob, it'll come out. Do you have an old brake hose that you can cut? (any old brake hose with a banjo fitting will do) If so, bolt the brake hose on to the caliper, then take it back to the gas station and put the airhose nozzle hard up against the cut end of the hose and fire away, it'll come out.

 If you don't have an old hose you'll have to reconnect the caliper to the brake line and pump that piston out, but it'll take forever. Cheers, Terry.

[Steve F]

Greetings.  What I've done successfuly was to attach a grease gun to an open bleeder, with a bolt screwed gently into the brakeline hole.  Pump it full of grease, and it gradually and safely pumps right out, without any sudden bang like you'll get from compressed air.  On the down side, you have to clean out the grease when you're done but that only takes 2 minutes.

[Bob Wessner]

I've used the same method as Steve, works great, couldn't believe how easy it slipped out. Wipe out most of the grease with a rag, then drop the caliper half in a tray of solvent for a while, clean-up is pretty easy.

[Gordon]

Have you tried pushing it out with the master cylinder?  Just connect the caliper brake line directly to the MC, and pump away. 

[rob]

Hi everyone,

The problem is, is that the piston has a grove around it, that apparently isn't supposed to go into the caliper housing, and now i've managed to get it past the groove where the O-ring fits.  So its not just a pressure fit that is holding it is, it is actually catching with the metal, and I am not sure if I will be able to get it past.

I will try these though, hopefully something will work!

rob

[Bob Wessner]

If worst comes to worst, maybe someone can suggest a liquid that can be put in around the piston from the outside that will pretty much disintegrate the rubber to the point it will allow the piston lip to pass, but not harm the piston or caliper. It would require a new piston seal after a thurough cleaning, but it might work.

[Tim.]

Wouldn't carb cleaner make pretty short work of the brake seal?  There's nothing else to damage in there, so perhaps a long bath would do the trick.

[Bob Wessner]

Probably the ChemDip variety might work. Yamaha, I don't think will, as it is 'safe' for rubber components. But then buying an entire bucket of the nasty stuff (gallon?) is a pretty costly way to disolve a seal.

[rob]

I dont think that its the rubber O-ring that its caught on, but the recessed groove in the cylinder wall to make use for it.

I went and tried to hook the caliper directly the master cylinder this morning, only to find that one of the master cylinder bolts is stripped, so iit will be another day before I can try to pump it out.. thanks!

Rob

[Jonesy]

I wouldn't try the solvents (carb cleaner, etc) since most of these will cause most rubber (not intended for fuel contact) to swell, which may compound the problem.

[rob]

Well...

I got a screw extractor and drilled a hole in the machine screw holding the master cylinder reservoir cap on, inserted the screw extractor, and had the extractor snap off in the hole!  I think the cosmos have conspired against me on this brake rebuild.

Thanks for the help everyone, I think I am going to hit the bottle for a few days, ignore it,  and hope it fixes itself.

Rob

[Terry in Australia]

That's the way mate, "If at first you don't succeed, see if the loser gets a prize", ha ha! The patented screw extractor was designed by a guy called "Murphy", and "Murphy's law" dictates that "If anything can go wrong, it will", so be prepared for more heartache and alcohol abuse as the restoration progresses.

When you eventually finish the resto and realize that you could have bought 2.5 new super-bikes for what it cost to rebuild your old bike, just remember this mantra: "I did it myself, it's a classic, you're just jealous!" Ha ha, Cheers, Terry.  

[rob]

The saga-continues,

With a raging hangover, I took it into the machine shop at the university I work at, and got a machinist to use a carbide drill bit to drill the screw head off, and then managed to bull the screw head off, and the reservoir cap.

In the process, the reservoir cap sustained some light damage, namely the screw hole and counter sink are pretty damanged, and it is unlikely that it will provide any seal.  His recommendation was to fill the hole screw hole in the reservoir cap with metal epoxy, then re-drill and counter-sink it.

Can anyone recommend some good metal epoxy?  Or any idea how metal epoxy will react with the brake fluid?

thanks,

Rob

[Bob Wessner]

I know JB Weld opoxy will hold up in direct contact with gasoline, not sure about brake fluid. You can get it in small tubes (takes two of course) at any hardware store. Mix a small amount and when it's cured, 24 hrs I think, drop it in some brake fluid and see what happens.

[rob]

Hi Bob,

Good stuff, i'll try it out.  I phoned the local honda dealer, and they have the reservoir cap in stock for $26 CAD.  I am just going to go the easy way out and get the new cap, as I am rather anxious to try and use the master cylinder to hopefully blow out the piston from the caliper (see beginning of thread if you don't know the saga).

I think that I will try to use the metal epoxy and drill it out on a rainy day though, its probably worthwhile to have backup parts!

Rob

[rob]

Hey everyone,

Thanks for all the feedback on this.

I just hooked the caliper directly up to the master cylinder, and manged to pump it out no sweat.  After shooting the piston out like a canon the first time with air, I think that using the brake pressure to get the piston out is a much nicer solution if you dont mind a little mess.

I just rebuilt both front calipers and got them back on the bike.  Thanks again.

Rob