1976 KZ400 D3 Front Brake Caliper Issues

Ill take some measurements tomorrow late day and post em here.

By alinaaseh: I made matters worse ...., and rounded the bolt in the process. No amount of WD40 & plying has made it budge.

If you're using regular wd40, that stuff really isn't a penetrating oil. it's just a light lubricant. They do now make a penetrant, claiming it's better than pb blaster. pbb didn't do as good as Liquid Wrench in a test floating around the internet.

For stuck bolts I use Liquid wrench penetrating spray lubricant. It's readily available & cheap. and it works.
Spray. tap tap tap the part with a hammer & wood block. repeat. let sit overnight. or several nights. spray. repeat.
Kroil is supposed to be best, but it's more expensive & I've never seen it in any auto parts store or hardware store.

Keep in mind that a penetrant may attack the rubber & plastic parts and will contaminate the brake fluid.
So you should remove the rubber/plastic parts before spraying, then disassemble & thoroughly clean everything afterwards.
If your bike has old old old rubber original brake lines, you should replace them.
....

I really like a 50/50 mix of acetone and ATF for penetrating oil. Works better than anything else i've used and is super cheap to make.

Hey,

I was unable to take a measurement because the caliper is all back together w fluid in and working, and didnt want to chance anything. I do have the 77 caliper there, I will take some measurements of that hopefully tomorrow. Sorry!

No eBay APP ID and/or Cert ID defined in Kunena configurationNo worries.
Mine is back together with the eBay oil seal. So far so good. No leaks and it seems to be working. I also switched over to DOT5 so I am working thru that as well. In any case, it's good to have the KZ400 back.
Here is the link for any other KZ400 people looking for the caliper seal:

Great news!

Update: The seal I purchased from the ebay link above has failed. The bike only has about 20 miles on it but the seal will no longer seal causing the brakes to seep fluid from the caliper.
Back to square one.

That bites.

To his credit the ebay seller has offered to send me another one and to help any way he can.