Which MC Rebuild Kit?

[lonelobo]

I need to rebuild the MC in the pic below. How do I know which rebuild kit to order? The body is so corroded I can't see any markings. I have a lot of experience with Electrolysis to remove rust from vintage woodworking tools and plan on removing the rust that way, which is the easiest and most thorough and non-destructive way I can think of. Any ideas how to ID the MC before electrolysis?

 

[26667]

Mine had problems, too. ('78 RS) and guru said that tho' the re-build kit is only about $60, if that don't fix it and you must replace more than just what's included in that kit, you'll have to spend $360 on the whole thing anyway and duplicate the re-build kit.

I spent the $360

good luck

 

[108625]

Lonelobo,

Odds are if it leaked fluid out (which it did, stripping paint and rusting your frame),
it let moisture in. It's a safe bet the cylinder bore is corroded and a rebuild kit won't fix that.
You could buy new, or look for a better candidate for rebuilding used.

Bob

 

[beemerman77]

master cylinder repair

converted a 77 / 7 to dual disc. needed a 17mm master cylinder "under tank" to replace the 14mm used with the single disc.found the best one i could , it still had a ridge in the bore. i consulted loctite corporation. "we use many of there products where i work"
explained to them was needing to repair a master cylinder bore and that the repair would be in brake fluid forever
loctite ,no problem , i said brake fluid , loctite responded no problem and recomended
loctite superior metal # 97473 , purchased some , approx. $80.00 for 1 pound minimum amount able to buy " life time supply " it is a 2 part filler / epoxy it is on the thick side when mixed and easy to use, plenty off working time. loctite highly recommends glass beading the area for repair. i disassembled the master cylinder . into the blast cabinet it went , then a through cleaning with acetone. the locktite comes with a very good spatula , a little thinning down with a knife and its the perfect size. mixed up superior metal and smeared it into the bore of the master cylinder. then to napa for a vw brake cylinder hone. after cure of repair , set master cylinder in a bucket of kerosene and honed, frequent inspections to get the feel for how much i was cutting during honing.this stuff is hard when cured and hones slow.finished honing washed with acetone and inspected, perfect finish,can not tell it was repaired, used a bore gage and measured a smidgon over 17mm. master cylinder been on bike for a little over 5 years now, me being skeptical of epoxies and such. pulled cylinder off last year disassembled and inspected. looks like new / the day it was put on,and because it is a " repair filler it will not corrode.
this worked for me , might be worth a try. note loctite also offers the same stuff for aluminum. think lower fork leg scratch repair,yup, works excellent there to
check out loctite's web sight

 

[lonelobo]

Thanks for the responses

I bought a better (off a parted out RM90S) MC and lines for $75 off of Ebay. I needed the rebuild kit for mine AND a new cap/float and the total for both of those was close to $100. Now I could be surprised by a bad MC but the seller said it was ready to be put on a bike, soooooo...we shall see. Parts are coming in like crazy and it's like Christmas every day.

 

[crazydrummerdude]

I bought a better (off a parted out RM90S) MC and lines for $75 off of Ebay. I needed the rebuild kit for mine AND a new cap/float and the total for both of those was close to $100. Now I could be surprised by a bad MC but the seller said it was ready to be put on a bike, soooooo...we shall see. Parts are coming in like crazy and it's like Christmas every day.

Sweet deal.

Man, people really shot down the rebuild idea, though. My MC was waaaayyy worse than that, and I bought a rebuild kit, cleaned it up, and it hasn't leaked a drop in 3.5 years.