Front caliper has a case of the weeble-wobbles

Just picked up an 82 xj550, and i can grab the front caliper and clunk it back and forth a good quarter inch (fore and aft). The pads stay on the disk but i've never seen any brake do this and i don't know how much it's supposed to float. I'll take a video once i get home from work, (with pictures for you) but I'm just looking for any clues as to a possible problem here.

 

The caliper should 'pivot' (more noticeably without pads on), back and forth is bad.

It is possible that the inner sleeve for the pivot bolt is missing. You need to disassemble and inspect.

Probably wise to rebuild the caliper, master cylinder and replace rubber hoses with braided stainless steel. And then there's your rear brake and delamination concerns. These are great bikes, but - not knowing exactly what the Previous Owner did to it, you will need to invest some time and at least $800 to make the bike safe and reliable.

Ask a bunch of questions here if you aren't sure - a lot of wisdom floats around in this community.

 

On the XJ550, XJ750 Seca/Euro, and XJ1100 (and some XS1100 models), the caliper body "floats" on the caliper mounting bracket......the main body is held to the mounting bracket via a pin, and this pin can get worn and/or the mounting holes can get "oval-ed" from use over time. Careful inspection is critical in determining whether the mounting bracket and/or main caliper body has deformed holes (there is no easy fix for this issue besides replacement).

ADDITIONALLY, these models can be equipped with very thin (.10 - .50mm thick) shims in-between the mounting bracket and the main caliper body. These L-shaped shims fit underneath the L-shaped steel plate that snaps onto the bottom of the mounting bracket. The shims take up clearances that exist between the mounting bracket and the caliper body, due to manufacturing tolerances and wear/age (kinda like using different thickness of valve shims). MOST original calipers did NOT use any spacer shims, so if you don't find any under that L-shaped steel plate, don't be surprised. But they were originally offered by Yamaha to allow any "slop" between the mounting bracket and the caliper body to be eliminated. We should have replacement shims available in the near future.

BTW, the only place you'll ever see these shims shown in the Yamaha literature is in the 1982 XJ1100 front caliper exploded view parts diagram; on all other models, many of the smaller component pieces of the calipers are not illustrated (and all of these models use the same caliper and mounting bracket).

Thru some trial-and-error testing, we've determined that, when assembled, there should be about 0.05mm (..002") clearance between the caliper body and the mounting block, without any pin binding. That clearance can be managed via the use of these shims.

 

His model is a 550, and they use a"traditional" caliper that floats in-and-out, rather than the goofy XJ650 / XS1100 / XJ1100 (rear) caliper that pivots from a single rear mounting point (only those calipers use the internal sleeve around the single pivot bolt).

 

uh oh - color me goofy with my XJ650!
Chacal - thank YOU for clarifying this.

Apologies to Omnideuce - I wasn't trying to muddy the waters for you.

 

Already has stainless hose. Shims eh? Might try shimming some clunk out. I've had the back brakes apart on my 400 probably a dozen times since i've owned it and i've never had any problems, and damned if i can figure out what i did.

 

I would inspect the pin and pin holes in the caliper body and the mounting bracket, that's a LOT of slop in that caliper.

Starts up like an XJ should though!

 

Mounting bracket is solid. The pin with the two boots on it that isn't holding the pads, yes?

 

Yes, that pin (it's the one with the round head and go thru the rubber bellow-booties) and the its passage hole in both the mounting bracket and the caliper body (i.e. what locks the caliper body to the mounting bracket). The steel pin can oval-out either or both of the passage holes, thus creating slop.