Spongy front brakes.

[cl4yd0h]

I did a rebuild kit on the master cylinder, pulled apart the old calipers, cleaned everything up, new pads, flushed an entire bottle of brake fluid through the lines and threw my bleeder valve on until I couldn't get anymore bubbles.

They work ok, It is still very spongy at the handle, I can pull it all the way back to the grip with a firm pull.

What can I do to tighten these up?

[r3tro74]

My 74 gt550 had the same problem. I loosened the M/C handle bar clamp bolts and slid the M/C out to the end of the handle bar so when squeezing the lever, it would fully bottom the piston in the bore without contacting the handle bars. Also Bled it with the M/C rotated on the bars at different angles. Bleeding at the line nut at the M/C- tighten nut, squeeze lever, slightly loosen line nut(with a rag wraped around it) until lever bottoms, hold lever untill nut is tightened, release lever.- repeat with M/C and or bars in different positions.
Mine had the seperate plastic resovoir that screwed to the master cylinder. I think air was trapped under resovoir. Also be sure both of the holes under the resovoir (it the metal casting) are open one of them is quite small and might be plugged up.

[Vintageman]

cl4yd0h,

Did you note the the master cylinder has two holes for the fluid reservoir interface. Mine had plastic reservoir, I removed and saw one large hole, but there is second smaller hole too and it was plugged. That cured my issue and tight now.

Else if you rebuild msater correclty you still have air?