Brake Rebuild

Today's main task was to rebuild the brakes.  

Dad had put the new o-ring on the master cylinder piston, but it would not move freely.  It was one from an auto parts store and was just too thick. So we put the old o-ring back on since it seemed to be in good shape.

We bolting the master cylinder onto the kart...  OOPS.. Better work on the brake tether first... so take it back off.  Practice makes perfect.

A cable brake tether is a mandatory safety device on all karts today.  We need to drill a hole in the lever on the master cylinder lever.  Here it is ready to drill.  However, the bits we used did not touch the surface.  So it will need to be taken to uncle Jim Toney or a local shop.

Our question all along has been "should we rebuild the _____ ?"   The quick (and bad) answer is "no, what could be wrong?"  The answer should always be "Yes!"   We are both very glad we elected to rebuild the brakes.


Each kit came with a new piston head, a stainless thick washer, and a couple o-rings.  Here is the brake piston head and shaft after being taken apart.  Such a simple design.   We still don't know why they are different pieces, but probably one single piece would easily break.

 Notice the old brake fluid inside the piston.

The small o-ring in the brake housing seals around the shaft.  It is held in place by the super-thin washer, the thick stainless washer and then the spring washer.  At first, it looked like the o-ring just sat in a crevice which was caked with white grime.  Only while cleaning the grime with a flat-head screw driver did Dad pop out all three pieces.  OH, that is where these new pieces go!

After cleaning all the grime with gasoline and scraping, everything went back together quickly.  One tough thing was getting the piston back into the housing.  A gentle pressure by hand got it started then a few gentle taps with a hammer got the piston flush with the housing.

Then we bolted the first brake onto the right rear of the kart. We were very careful to get the aluminum block on the inside of the frame, then the inner shoe assembly then the shim, then the outer piston assembly with the old puck added.   "Wait a minute!  This ain't right!"  There was about a quarter inch play in the whole thing.  Funny... it matched the thickness of the puck.  So back over to the workbench to gently compress the piston down enough to receive the puck.  Finally... here are both assemblies, REALLY ready.

 And here is the right rear brake all put together, bright and new.

 While tightening the last bolt on the left brake, it stripped.  Dang!   Tried to fit it to the tap & die, but no use.   So we headed back to Menards (MAY-nards) to get a replacement bolt and another crown nut for the axle. No 3/8" bolt so we went with a 10mm bolt.  Guess what?  10mm is actually .393" and will not fit in a hole for a .375"bolt.  And no castle nut at either Maynards or Lowes.

Very frustrating.  Then Dad wonders what is on the other kart.  DING DING DING.  He looks and sure enough, the are correct crown nuts on the front spindles AND correct bolts for the brake assembly.  They are short bolts, so we will delete the aluminum block from the set up.  This got us to wonder why the aluminum block is there.  The other kart does not have it.  So next time, we will try it without.  

Finally, we connected the brake lines and taped the keys holding the brake disk in place.  Next time will be "Brakes Rebuild 3"