Rear caliper questions

still working on the 76 zk750. Apparently the dust boots between the mounting bolts aren't in very good shape - no problem. I can find those. a ridiculous $6 a piece but ok. there are these little metal like caps that the O rings sit in that are under the dust boots. These little metal caps are damaged - what do I do about that? I don't see them sold anywhere. The O rings are fine but this little metal cap thing seems important so I'm a bit at a loss.

those dont show up in the parts fiche for a 76 750. are you sure it is the stock brake? do you have a photo of the whole caliper?

Here are some pictures of the caliper and one of the master cylinder.






master cylinder is off in the penalty box right now soaking - waiting on parts so I don't have a picture of them together.

I too have those little brass boots on my 76 750 twin. Also pretty sure they are stock, I'm the second owner and it only had 6000 miles on it and sure enough they dont show on Partzilla. The pics look identical to my caliper and m/c.

You can get a whole caliper rebuild kit from Powerhouse Automotive in the UK for 27GBP which is a lot better price than Partzilla.

stores.ebay.co.uk/Powerhouse-Automotive-...0+rear+brake+caliper

Alas the kit doesnt include the brass boots, I wonder if they are really needed as they seem redundant with the rubber boots.

they hold O rings in place - without them or something in their place the O ring that the bolt goes through can't be where it needs to be for reassembly. I'm still chewing on possible solutions for my dilemma.

Pretty sure I put the O rings (4) into little grooves machined into the body of the caliper itself then the bolts go through (quite snugly).

I'm a noob though but theres some guys here that know these twins so maybe one of them will chime in.

That is interesting - I hadn't really looked at the caliper for a place to put the o ring. I will definitely go look into that.

That is the correct stock caliper. I rebuilt that same caliper a couple years ago and it did not have the brass caps. The o rings go in the carrier with some silicone grease to allow the caliper to "float" on the disk. I'm not sure why the brass parts are there but they shouldn't have anything to do with the functionality of the caliper, if anything they will allow the dust covers to be more secure.

Also before you go buy the rebuild kits for either of your master cylinders take them apart and inspect the steel bore, if it is pitted or corroded you will probably need a new MC. I have tried twice to "rehone" the bore and both times it did not work. In that case I would just buy a new MC on ebay from China. I have used two Chinese masters on bikes i have flipped and they work great.

Thank you for the info.

The calipers from what I can tell right now are going to work fine as they are. They aren't seized but I wont know for sure until I get the master cylinders worked out to see if they'll work. I got the rear caliper back on and I think everything will be good to go when the master cylinder is operational again.

The master cylinder bores are good - the pistons were just stuck with some yellowy caked on gunk. I am going to run with the suggestion from another user to just buy new for the front master cylinder since the price difference is very little. The rear I have some parts coming for and I'll know more at the end of the week when they get here.

I was able to work out my problem using some old valve stem seals. I recently rebuilt an engine and transmission for my firebird and the valve stem seals worked nicely to hold the o ring and dust boot in place for re-installing the caliper. My master cylinder stuff also arrived and my back brakes are now fully functional.

Thanks to all for the help

DoctoRot wrote: Also before you go buy the rebuild kits for either of your master cylinders take them apart and inspect the steel bore, if it is pitted or corroded you will probably need a new MC. I have tried twice to "rehone" the bore and both times it did not work. In that case I would just buy a new MC on ebay from China. I have used two Chinese masters on bikes i have flipped and they work great.

My eBay-fu skills aren't so good I guess cause I can't find a new knockoff rear m/c. Any chance you've still got a link Doc?

From my looking around there really isn't much to choose from aftermarket. I found a used one on eBay for 20. They said it needed rebuilt but everything seemed fine. I found rebuild kits that looked right but not much in the way of new