Since there have been a few people talking about how thier front " Re-Slieved" master cylinders have frozen up on them I'm wondering if this is a design flaw or if some do it differantly & one or another way will freeze up but some others don't. Has anyone had the M.C. Slieved by Al Miles or using his kit had it lock up? Or have all the ones that have locked up been done with some one elses kit (if there even is one). I'm trying to deciffer why some have had problems & some don't. Thanks.
History of Master Cylinder lock ups.
- Thread starter gtsun
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Mine from Miles Eng. did not "lock-up " the brake at all but after only 2 1/2 yrs. the piston assembly nipped up with no movement. Clean fluid too. He seemed surprised this would happen and shipped me another for small cost. To tell you the truth it sits in the box and I went to Mike's XS .com for a yamahaha unit that is just fine but had to have the braided brake line end changed to metric to fit.
Bummer Maylar that is NOT what I wanted to hear. I'm still using a Miles one that was done by a very well thought of Norton mechanic. Never had any problems & am going to mount a Brembo MC as soon as I have deceided which switch to use for my turn signals, horn, Hi-lo etc... Since we now now all the kits will lock up, Im thinking it's the differant workmanship / tool specs. Please if you did one don't think I'm saying your work is questianable. I am not. Just wondering why some lock up & some do no because I have a few good rides planned before I can change it out.
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Mine has locked several times and it has always been on a very hot day and usually after the bike has been parked in the sun for awhile, so I try to cover it now when parked on hot days...and usually ride another bike when heat is extreme, my Norton does not seem to like that much heat in general. Not sure who did the resleeve job, the PO had it done a couple of years ago.
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Rust and crust can lock up any piston but otherwise the only lock ups concern the piston returning enough to uncover the pressure relief port when fluid pressure is higher d/t the temperature expansion. The cure for this is relieving the plunger spacer the lever works on or the lever pad itself. Collapsed hoses internally can mimic this. Been a few reports of factory piston slightly wrong length too. Usually just take a few thousandths off but that does take off some lever travel for pressure stroke, which should not matter but a bit closer to grip on full squeeze.
Until i got confident I'd taken mine down enough for full sun summer I put a ball cap or wet towel on the mastercylinder so freaked out to have a lock up dump again.
Until i got confident I'd taken mine down enough for full sun summer I put a ball cap or wet towel on the mastercylinder so freaked out to have a lock up dump again.
jaydee75
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I recently resleeved my own MC using a Harley 1/2" seal kit. The sleeve must have two holes in it. I observed while drilling the sleeve that the placement of the holes relative to the piston are super-critical. If the front seal doesn't move back enough to clear the very small relief hole, the brake cannot release. It would be easy for a shop to put a piston in that was off a few thousandths and match up badly with the sleeve vent due to it's allowable tolerances. Heat would aggravate the mis-match and cause problems.
The only thing I can recommend for peace of mind is to remove the piston and measure it carefully with respect to the sleeve vent hole and see how much overlap you have. Those who have a working sleeve job needn't worry, the geometry can't change.
JD75
The only thing I can recommend for peace of mind is to remove the piston and measure it carefully with respect to the sleeve vent hole and see how much overlap you have. Those who have a working sleeve job needn't worry, the geometry can't change.
JD75
elefantrider
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Also interested on how this resleeve kit is performing long term.
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The master cylinder on my MK3 was locking up BEFORE I had it resleeved, but after locking up it would free up again after 30 seconds or so. Basically, the piston/seals were shot and the piston return was "lazy" at times. I went with the Old Britts resleeve which included instructions on how to verify that the resleeved MC would allow the relief port to be uncovered using your existing brake lever, and what to do about it if the test failed. Very handy. I combined the new resleeve with a complete cleaning and rebuild of the entire brake system (new stainless pistons in the caliper and new braided brake lines). Works nicely now.
Keep in mind that resleeving does not mean you'll never need another MC rebuild. Eventually the piston/seals will fail and you'll need to refurbish again to keep it working properly.
Keep in mind that resleeving does not mean you'll never need another MC rebuild. Eventually the piston/seals will fail and you'll need to refurbish again to keep it working properly.
tpeever said:
That would be Al Miles.
Mine, by Al via Old Britts, locked up a couple months ago. Al and Fred (at Old Britts) had very helpful advice about fixing it. In my case, it turns out the port in the M/C was blocked with some black stuff that I have to believe is part of a degraded O-ring or similar rubber part. Heat does not seem to have anything to do with it in my case as I'd only been out of a shady garage for a few miles at the time.
Onder
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Makes me wonder what sort of brake lines you have and how old they are.
Also Ive gone to silicone fluid anybody else using it? I know the warnings but I also
know my guard stay has a blister on it and it was brand new. Out with the evil
paint remover brake fluid.
Im keeping a careful eye on all this.
Also Ive gone to silicone fluid anybody else using it? I know the warnings but I also
know my guard stay has a blister on it and it was brand new. Out with the evil
paint remover brake fluid.
Im keeping a careful eye on all this.
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I did my own resleeved job, including making a new designed piston to which I fitted 2 12mm brake seals. My design incorporates a cap at the end of the piston to which I can add or subtract shims to get the right clearance for the relief hole. I have been involved with re-sleeving master cylinders on classic cars for years and have never had a problem. I looked at the design for a resleeved kit which involved putting a thread in the master cylinder and tossed that idea away. My sleeve is a slight press fit in with Loctite.
regards, Dereck
regards, Dereck
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My Al Miles resleeve worked great for years till I bent the stock brake lever and replaced with what I thought was the same OEM lever. Ensued was two warped rotors several back and forths with Al, endless attempts at bleeding the brakes and rebuilding caliper. Seems that the brake lever was out of spec not allowing the brake fluid return to completely open. It was hell, but finally working again.
Onder
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Bit slow in responding, pardon, yes I have gone to DOT 5. Only a few months but no leaks and it sure stops
hard on two fingers. That is a sleeved master and rebuilt caliper with a ground and lightened rotor.
Rear shoe brake remains a hollow joke.
hard on two fingers. That is a sleeved master and rebuilt caliper with a ground and lightened rotor.
Rear shoe brake remains a hollow joke.
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Talked in depth with Mr. Miles for a good while from California. No blame placed after talk. Tolerances run real close. Clean fluid. But it did happen. Rebuilt unit good so far. :|
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