Front brake caliper seals......

Okay, I ordered the front caliper "rebuild" kit from Old Bike Barn for the '82 XJ750 and got it in today, went to install it and the inner seal/o-ring is just right, but the thinner "outer" seal/o-ring that is provided in the kit is only about 75% as thick as the original, meaning it won't fill the machined recess in the caliper body fully.....wtf?

Has anyone else had this problem, the part they sent me is made by Tour Max and is OBB part 29-0126, as seen here:

http://www.oldbikebarn.com/motorcycle_p ... bike=XJ750

Has anyone had any experience with any other brand of front caliper rebuild kits where the seals are the same size as the original? I'm very leery of using this kit, I know the outer seal is just, in essence, a dust boot but it seems that it will start rolling over in the groove as the piston travels back and forth and that will cause all sorts of problems.......

 

chacal , that presumption is a good one i think , it probably would roll , thats all i can offer as i used the kit from yammyhome...

 

Unfortunately, I don't see where Yamaha offers the seals anymore or a caliper rebuild kit for this model.........

 

I'll compare your calipers to my 82 turbos. I bought the stock kits last year. If they are the same, odds are good you can pull parts out of another kit to match up. I'll check tonight.

 

Don't panic.

The INNER Seal is the MAIN fluid seal and needs to be tight fitting.

The OUTER "Seal" is a Dust Seal. The outer seal is less tight fitting to allow the caliper piston to retract -- ever so slightly -- when brake pressure is released.

Start with a perfectly cleaned caliper body and both ring-seal channels absolutely free from contamination. If its not aluminum; clean it out!

Lube caliper cylinder and channels with lots of NEW brake fluid.
Lube the seals with lots of New brake fluid.
Lube the piston with lots of NEW brake fluid.

Square-up the piston and press it in. Use a "C-clamp" and a Large Socket placed inside the piston and Press it in nice and slow.

Keep the piston lubed with brake fluid until its pressed home.

 

Hey Rick, thanks for the input. I know the install procedure is pretty straightforward, and gosh if I say so myself, I sure have gotten the caliper squeaky clean, including the seal channels (glass-beaded clean).

The problemo is that the replacement "outer" seal included in the rebuild kit is only about 75% as thick as the original:

Original outer "dust" seal:

0.106" thickness (top to bottom).....in other words, the edge that actually rubs against the piston.

Replacement outer "dust" seal:

0.075 thickness (top to bottom).


This reduced thickness leaves a gap of 0.030 where the seal fits in the seal channel in the caliper.....thus the seal will be able to walk in-and-out (in the same direction as the piston) as the piston extends and retracts. The seal channel is approx. 0.031 wider than the replacement seal.

Although I know that this seal will be pinched really tight against the piston and the caliper seal channel land, and even though it's not a fluid seal, it still seems that as the piston goes through its (admittedly) small movements, that it will try to roll the square seal or perhaps even get the piston slightly cocked within the bore.

I've looked in the McMaster Carr catalog and they don't seem to have much of a selection of square "o"-rings.

The original outer seals are in bad shape and can't be re-used, so that isn't an option.

Any thoughts on whether I'm being too anal, or where I might find a correct seal, would be appreciated!

 

The seal might stretch to fill the land once it's wrapped around the piston. Why not put the seal on the piston and re-measure the o.d..

 

Scratch that. I'm confusing diameter and thickness.

 

I got Yamaha stuff by mail order from England. Bloody expensive, as per Yamaha OE. Missing was the caliper bolt seals, which is a bit annoying. Anybody know who supplies these ?

 

Hi yepper, any chance you can recall or direct me to what place in England carries the OE yamaha caliper seals?

The accordian boots....at least for the 750 calipers....are available from Yamaha (they aren't cheap, though) and they fit perfectly. You can get them at a discount from places like www.bikebandit.com.

 

cool - thanks for that, chacal.

I got them from -

Motomax
65 High St.
Caterham-on-the Hill,
Surrey
CR3 5UF
England

tel. 00 44 1883 330655

Nice guy there, and good delivery. A little short of £25 but that incl. about £5 post to Ireland - say £20 for the goods.

PM me if you need any more info - I've got details of a couple of other UK Yamaha specialists. Good luck.

 

Thanks yepper.....by any chance do they have a website address? Would like to see if they have what I need before I call overseas!

 

I ordered from Yamaha (pricey-mid 40's) the caliper piston kit. It came with both seals, grease and of course piston. fit great.


was for 81 xj 750 seca..unsure if you have maxim or?? and unsure if different..

 

I ordered a seal kit for my bike from local Yamaha shop, got the kit pretty quickly, but was not cheap!

 

Hey everyone, it's getting time to do the winter work, including the brake swap. Does anyone have a set of XJ750 calipers that is off their bike and mind measuring the outer (dust) seal land width for me?

Hint, you'll probably need a digital micrometer to take the proper measurement..........

I've bought three different brand rebuild kits for these calipers and in all of them, the inner (fluid) seal is the correct diameter and thickness and the outer (dust) seal is the correct diameters (both ID and OD) but a much "thinner" thickness (106" original vs. .075" replacement). I'm beginning to wonder if these calipers are off a 750 or something else? (I bought them used from a forum member who says he bought them used from someone else). They sure LOOK like XJ750 calipers, as per the Haynes manual diagrams and the on-line parts suppliers exploded diagrams. Is there any other caliper that looks just like this one?

BTW, of the three caliper rebuild sets that I ordered, the outer seal that comes with the factory Yamaha piston (kit) is the widest by far, about .010". wider than what's in the other aftermarket rebuild kits. Like I said, in all the kits I ordered, the inner (fluid) seals are all identical in appearance, ID, OD, and thickness/width (except for the slightly wider fOEM Yamaha seal).