‘77 kz650b1 front brake caliper

Hi everyone I’m new here so bear with me. Recently purchased’77 kz650b1 with 17 k miles but had been sitting for 4-5 years. I cleaned carbs and got her cranked sounds real good but have more tuning to do. My problem I’m having is putting rebuild kit in front brake caliper. It’s very difficult to get the two long bolts back thru the new rubber boots with the  I rings on there. My calipers when taken apart didn’t have o rings on the nipples under the rubber cups. Any suggestions on a good way to tackle this problem? Thanks I really enjoy this forum 

Welcome from the UK

See if this helps Memo. First of all, are you absolutely sure the caliper bracket didn't have the 4 o-rings in there? I've never taken one apart that didn't have them, unless someone had been there before you? They can be pretty elusive within the bolt bore ends if slathered in old grease! They sit in a land and are pretty flush with bore. Don't know where you sourced the replacement parts from but the o-ring size is critical. Should be 13mmOD X 10mmID X 1.5CS. Too thick and the rod will have a hard time going thru or if forced, bracket won't "float" as intended. I use a High Vacuum Silicone Grease to lube the bore/bolts before routing the bracket into the caliper. Why Silicone and not something like wheel bearing grease you might ask? While wheel bearing type grease will work its petroleum based and can weep out if heated-up and drip down on pads and disc. Loss of maximum braking is a result and contamination of pads. Silicone has different properties and stays in place. Anyhoot, make sure the two bolts smooth shank areas are free of any rust/gunk and are smooth. Scotchbrite or equivalent will suffice to clean. A couple pictures to assist. Identical to Yours,     Have Fun!        

Hey thanks so much for the reply. I’m a little confused are you saying that the o rings go on the outside of the 4 nipples on the bracket under the cups? Or do they go inside? 2 of the nipples have a groove around them and 2 do not. I got my kit from brakecrafters and I did not see any o rings when I took it apart but didn’t look on the inside of the 4 nipples. I know that they have them because my clymer Manuel shows them but of course it doesn’t point to where they go. 

After looking more closely at your pictures I now see that o ring goes inside the dang bore! How stupid of me! Do all 4 go inside? If so why do 2 of the nipples have grooves around them? I’ve watched the only video I could find on this particular bike and he really didn’t show where the o rings go just said put them on. I really think if you go to all the trouble to make videos well anyway I appreciate the guys that do that. You’ve helped me more than you know but unfortunately I’m on vacation for several weeks and won’t be able to apply this new knowledge but can’t wait to get home now and get this thing back together! Also since you seem very knowledgeable can you tell me if the k and L carb kits from eBay are good enough to use all the included parts. I purchased a cheap kit just for gaskets and cleaned up my old carb parts. I put back on bike and it did crank but didn’t run as it should. Timing and new points and condensers also good. The bike set for several years but it’s only got 17,000 miles and in good condition for 49 years old. Again thanks for your help