78 xs650 rear brake bleed

[furrygreg]

I put up with very weak rear disc brakes on my 78 xs650 cafe for about a year. When I was building my project a couple of years ago, I pulled the OEM rear brake master cylinder off for a Mike's XS unit as the original unit was in bad shape from having sat for about 20 years. I never could get the master cylinder from Mike's to work right. Don't know if they are all second right or maybe I just got a bad one. I kept the old unit from the build. Took it apart and cleaned the bore and all passages with 99% pure isopropyl alcohol. Bought a K&L rebuild kit from Old Bike Barn, and reassembled the "new" old master cylinder. Used Mityvac and bleeding directions posted elsewhere on this site to prebleed the entire assembly. GOT ALL THE AIR OUT! Installed the entire entire built up unit back onto the bike and bled it one more time. I now have all sorts of rear brake action going on! Very excited! Thanks for everyone who has ever posted about this problem in the past for all the guidance and help. Man i love this bike. My Harley gets lonely in the garage nowadays.

 

[retiredgentleman]

I put up with very weak rear disc brakes on my 78 xs650 cafe for about a year. When I was building my project a couple of years ago, I pulled the OEM rear brake master cylinder off for a Mike's XS unit as the original unit was in bad shape from having sat for about 20 years. I never could get the master cylinder from Mike's to work right. Don't know if they are all second right or maybe I just got a bad one. I kept the old unit from the build. Took it apart and cleaned the bore and all passages with 99% pure isopropyl alcohol. Bought a K&L rebuild kit from Old Bike Barn, and reassembled the "new" old master cylinder. Used Mityvac and bleeding directions posted elsewhere on this site to prebleed the entire assembly. GOT ALL THE AIR OUT! Installed the entire entire built up unit back onto the bike and bled it one more time. I now have all sorts of rear brake action going on! Very excited! Thanks for everyone who has ever posted about this problem in the past for all the guidance and help. Man i love this bike. My Harley gets lonely in the garage nowadays.

All I can say, is Mikesxs has come to be known as a source to buy a lot of crap components. Never confuse Mikesxs parts with the high quality OEM parts that came from Japan.

I tried using a pair of Mikesxs carb manifolds. They fit very badly and allowed air leakage, causing my idle to wander all over the place. Re-installed my 30+ year old OEM stock manifolds (excellent fit and no air leakage) and I'm still using them to-day.

Best not to use old rubber brake lines. Replace with braided steel lines.

I always pre-fill my brake lines before installing on the bike. That way there is almost no air to bleed, and a hard pedal/lever comes very quickly.