So I have rebuilt the front master and can't seem to get the sponginess out of the lever. Its about 3/4 of where it should be. Used pressure bleeder, system has all new fluid, new pads, zip tied lever over night. Anymore suggestions?
Suggestion #1 - Don't forget to remove the zip-tie !
#2 - If everything else is mechanically sound, then you still have air in the system.
#3 - This can also be attributed to the OEM rubber brake lines which were crap from the day they were made !
If they're originals, they a garbage and maybe even dangerous !
1980 KZ 1300 sr# KZT30A-009997
Always High - Know Fear !
Agree with everything Scotch states, especially about old original rubber lines expanding !
I have also found with many Jap bikes including the 1300, its worth removing the brake lever and using a long screw driver or metal rod instead to push the master cylinder piston when bleeding, as it ensures the WHOLE Stroke of the piston is used, rather than only part of it.
This increases pressure too and gets rid of more air in the system quicker.
On some vehicles I find it necessary to drive it then re-bleed. I think that sometimes there are small bubbles lodged that a short drive (probably vibration from the motor) will dislodge so you can get them to a place they can be released.
The fronts on Motorcycles are a PITA. I think this is because are brake lines are too large a diameter. Last month I built a new Sprint Car and went with AN2 lines (1/8") rather than the traditional AN3 (3/16") lines. Was dead easy to bleed - I suspect because 1/8" is too small to have the fluid squeeze by a bubble. I might switch my KZ to AN2 as well. BTW, driver loved the brakes with AN2 lines - and these are the exact same disks/callipers/pads that were on the old car at the end of last year.
If it's not an air bubble, and there are no leaks, I would suspect the lines are expanding.