Caliper Question

[TazzTheJynx]

I have a question the front caliper. I want to get a new one, since the piston is completely rusted and refuses to budge.. I need a new caliper, or find a way to rebuild the one I have. However, I heard the calipers on these things suck anyway (and with only a single piston on mine? Or am I missing half of it?) I was debating on getting a caliper from another bike and just throwing it on there. I'm new to motorcycles in general and haven't messed with brakes before, so are there certain dimensions I need to be aware of for the caliper I buy? Or should any ol' caliper fit?

I have a 1981 xs400

 

[rshutchinson]

You can remove tje caliper. Block the banjo hole with a properly fitting bolt and then crack the bleeder a little, attach an air hose and blow it out with compressed air.

If that doesn't work, you can also use a grease gun to squeeze the piston out.

I think that's worth a try first. If you can get it out and find that the bore of the caliper is not pitted its certainly rebuildable. You can buy new pistons and seals.

 

[Wolfe_11B]

The stock caliper is more than adequate for the bike. It's not a bad design at all, and more than enough for a 30 some odd HP bike.

No caliper other than stock will just bolt on without modifications. You have to deal with the fork mounting, caliper spacing, and disc spacing.

You can use other calipers, but there is quite a bit of thought that needs to go into it. You can rig up adapters for the mount, but a bit of cnc or a bridgeport is needed to do that properly. There is also some mechanical engineering 'math' involved, and most adapters I've seen people make don't take into account the shifts in the forces on the cast fork mounts. This image should be enough to make you not want to do it-

Also, switching calipers usually requires finding a matching master cylinder. This page is a good reference-
http://www.vintagebrake.com/mastercylinder.htm

Use the stock caliper. Its a floating design that works great with a rigid mounted disc. If you switch to a different caliper design, you'll need to think about switching to a semi floating rotor to get things proper.

If you do end up trying to source a caliper, keep in mind that they were different on a few years. You want one made for the later model forks.

 

[TazzTheJynx]

Well, here's a picture of my caliper... You guys can try to decide if it's worth saving, if you think it is then yea i'll try and see what I can do with it..

 

[kshansen]

The rust I see inside the piston is not anything I would loose sleep over. What I would want to see is the outside surface where the seal ring rides.

Not sure if replacement pistons are available, quick look at Mike's did not show any.

Before I condemned the calipers I would at the least remove the pistons and clean them up, might only need a set of seals and a bit of cleaning.

One easy way to get piston out is to hook it back up to the hose and bleed the air out and then just pump the brake lever to push it out.

Did a quick Google search on Yamaha brake pistons and this one popped up. Don't know anything about them but looks like $28.00 for a new stainless steel piston!
http://www.hvccycle.net/yamaha-brake-caliper-pistons/

 

[TazzTheJynx]

Alright, after I finish wiring i'll get the piston out.

 

[kshansen]

You replied as I was editing the message, check out the link to the place that claims to have new pistons for $28.00

 

[rshutchinson]

Sci here in Ontario also has new pistons. Just have to measure the dimensions. I can look through my emails to see what one I ordered for my dads.

 

[drewpy]

I got my made in stainless, then they were selling them on ebay for £20, no brainer

RD400E, xs750, xs 850 xs 1100 and xs650 use the same just confirm caliper with a visual

 

[xschris]

The rust I see inside the piston is not anything I would loose sleep over. What I would want to see is the outside surface where the seal ring rides.

Not sure if replacement pistons are available, quick look at Mike's did not show any.

Before I condemned the calipers I would at the least remove the pistons and clean them up, might only need a set of seals and a bit of cleaning.

One easy way to get piston out is to hook it back up to the hose and bleed the air out and then just pump the brake lever to push it out.

Did a quick Google search on Yamaha brake pistons and this one popped up. Don't know anything about them but looks like $28.00 for a new stainless steel piston!
http://www.hvccycle.net/yamaha-brake-caliper-pistons/

I put one of those ss pistons in my 81 work/fits fine. Make sure to get a new seal kit