When I got this scooter, which had been stored outside for years, the rear brake shoes rubbed. Wheel cylinder was frozen. So I rebuilt the master cylinder, which had some pitting in the cylinder area. Installed a new wheel cylinder and bled the lines with a Mity-Vac. Put it all together and when I pressed the brake pedal, it locked the rear wheel. Shoes are stuck once again.

I'm goonna go crack a line. If the wheel unsticks, then it's probably master cylinder, right?

Should you be able to press the plunger in the master cylinder and have it return on a bench, or is it supposed to be tight? Manual says to toss if pitted, so pretty sure this is my problem. What else could it be? Manual says not to hone, get a new one. JP so far the cheapest at $73.

 

I have the same problem with my '72 FLH. To get through the rest of the season, I just adjusted the shoes so they don't contact the drum, and I just use the front brake for now. Going to rebuild the system this winter, I'm thinking the rubber line is probably breaking down inside and not letting the fluid back, so it's building pressure.

 

I've rebuilt the old cast iron MC's before with no issues, just make sure it hones straight and even is all.

 

Replace the rubber line. They do go bad and collapse on the inside.

 

Manual says not to hone MC...but I did and it's fine. Now I just have to adjust the shoes and had to order a 3/8 pipe plug socket because a regular 3/8 open end was rounding the nuts. If you screw those adjusting nuts up, do you have to get a new backing plate?

Swap meet Morris, IL this weekend. Yeeha! Hope to score. Dual disc front wheel and fab some brackets so I can use the old time adjustable stock front end.

 

Way back when I wanted to lose the drum front brake after a hair raising trip through Colorado I ended up with a pie slice caliper off a sporty I think and a 21" wheel from a swap meet. Bracket I rigged up out of scrap metal was ugly but worked for a few years . Didn't have a torch to bend anything just a cheap vise and a hammer.

 

A 3/8 extension will fit the cams on the backing plate and keep you from rounding it off.