Shout Out - Apple Hydraulics

[RPGR90s]

I had Apple Hydraulics re-sleeve the original master cylinder on my '74 R90s and it came out great.

With 150k, my last rebuild (new piston and seal) was still allowing a drip or two of brake fluid in the rubber catch boot, so I took advantage of their re-sleeving service.

Got it back, bench bleeded the M/C, hooked up the lines and finished the final bleed. Took all of 20 min.

https://www.applehydraulicsonline.c...ycles/products/bmw-motorcycle-master-cylinder

Good people. I'm just a customer.

 

[20774]

Nice to hear positive feedback. I'll add a little more context to the thread title for future searches.

 

[syvrider]

I was just wondering about this topic. I'm refreshing a new-to-me 92 GS. From peeling paint and stuck bolts I knew the MC must be leaking. I ordered the new piston kit and o-ring and cleaned up the sleeve and other lever parts.

It's not back together yet. But when it is...what if it still leaks? Is that the sign that I need a new housing with sleeve?


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[20774]

What was the condition of the master cylinder sleeve? Did you shine a light down the bore and see the surface? If it's pitted, then you'll need to either hone it to take out those pits which tend to cut the o-ring. If it's severely pitted, then you likely can't just do a simple hone and get rid of the pits. Brook Reams showed on one of the bikes he was working on his process to hone the cylinder bore. He used a good wooden dowel that was wrapped in some sandpaper which IIRC he was able to chuck up in a drill and then make some passes on the bore...maybe he just turned by hand. It's similar to what you might do on a cylinder.

One thing to remember when doing a yearly brake-bleed is to not push the piston travel to great extremes but rather just squeeze the hand lever about the same as you do during normal use in order to push new fluid from the reservoir to the brake caliper. Do so could push another otherwise good o-ring into some rough area in the bore.

 

[syvrider]

Got it. Will check the bore carefully.


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[syvrider]

Followed this advice. The bore had a bit of AlOx white scale. Polished it out with a wad of 0000 steel wool. Silky smooth now.


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