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    Brake master cylinder question.
    #1
    Millenium Member Xbird's Avatar
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    I'm using a lever-style "reservoir block" brake master that I originally thought was off of the LTZ. turns out it's not. Really not sure where I got it from, thinking it's original to the buggy I'm modifying-- mount and original rod length match.
    Anyway, my question pertains to the piston travel inside the bore. If I allow the lever to retract fully, it contacts the reservoir cap.
    If i cycle the piston with the lever thru its full stroke, I can hear air "gooshing" in and am getting brake fluid seeping out at the end of the bore.
    If i cycle it where i limit the piston travel so the lever does not return all the way back to the cap, it seems to hold the seal and not allow any air in. As shown below, it's limited by the rod, but not enough, I have to trim anouter 1/4-in. or so off the threaded end of the rod to get it to a "correct" position.

    There are no missing seals on the piston, the rod boot is worn, but that should not be an integral part of the sealing system of the bore. Anyone ever encounter this type of master on a quad etc.?? It seems that i will have to limit the travel using the rod adjustment so the piston doesn't back out. This seems correct, but a bit odd of a way to set one of these up. It also make it so that as soon as the rod is disconnected from the pedal, the piston kicks out and lets air in. I may have to weld a bead on the back of the lever to prevent this from happening.

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    Re: Brake master cylinder question.
    #2
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    Sounds like it's missing a snap ring.
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    Re: Brake master cylinder question.
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    Millenium Member Xbird's Avatar
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    Good point Liduno. i'll have to look for a groove inside the start of the bore. the boot has a metal ring inside the lip that has worn thru a little bit. It didn't have a snap ring holding the boot/ring in place when i took it apart, but that's not to say that it didn't originally. I know the narrow cylinder style masters have them. If it is designed with one, I could see that it might retain the piston enough to prevent the rearwards travel causing the problem. I have to take the hose off to feed it through the body panel as it is, so no worries about refilling the system. I can't see that they'd design a master that would allow this to happen if the pedal rod was disconnected. The condition of the bore was good, didn't look like it was worn out at the end.
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    Re: Brake master cylinder question.
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    Millenium Member Xbird's Avatar
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    Well, this little bugger has me stymied. no snap ring groove, so i welded a lump to the backside of the pull lever to keep it from backing out fully. Still have a leak. the piston and seal are a different design from the more traditional atv push type masters, Finished the buggy today only to find a puddle under the lever and no brakes. If anyone has ever seen a master like this offered out there, please let me know. still searching but turning up nothing. really hate to have to redesign the entire system for a push master especially since everything is finished and painted.
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    Re: Brake master cylinder question.
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    Millenium Member Xbird's Avatar
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    looks like i found my answer, this is as close as i can find, and ironically, this is my buddy Randy's place right across the river whom I get my cro mo tubing from https://halfscale.com/product/master-cylinder/
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    Re: Brake master cylinder question.
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    Looks like a nice master.
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    Re: Brake master cylinder question.
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    Senior Member darwinpayne2000's Avatar
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    That's not a common design. I'm glad you found a replacement.
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    Re: Brake master cylinder question.
    #8
    Millenium Member Xbird's Avatar
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    Quote Originally Posted by darwinpayne2000 View Post
    That's not a common design. I'm glad you found a replacement.
    You and me both! Definitely not common, but for those working on smaller/lighter buggies, I'd suggest considering this type with the lever activation. It is sooooo much easier to package in and you get the benefit of easier effort setup/adjustment. What it would take me to strip tubing, fab up mounts and get a push type installed would add another week or two to the build and ruin a lot of finished work. Actually on my way to Randy's this morning to pick up the replacement, his place is right across the river from me.
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    Re: Brake master cylinder question.
    #9
    Senior Member mech_head6's Avatar
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    That is a common setup in the karting industry. There are many versions. I think they used it primarily for packaging and possible adjustment mid-race.

    I put together a setup that used a quad Rear Master Cylinder (RMC) with a lever link for a buddies kart. It's possible, but honestly easier to buy a setup like you are.
    Polaris RAGER 570/1000 S Hybrid
    • Engine - 2016 RZR 1k XP
    • Transmission - RZR 1k XP
    • Chassis - 2012 RZR 570
    • Suspension -
      • Front: RZR 800S A-arms/Ranger 900 XP hubs
      • Rear: Ranger 900 XP A-arm/hubs

    http://www.minibuggy.net/forum/utv-a...ld-hybrid.html


    "The grass isn't always greener, but the sun's always shining on the other side of the clouds."
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    Re: Brake master cylinder question.
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    Millenium Member Xbird's Avatar
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    The yerf spiderboxes use a long/short boomerang lever setup that i've mimicked a couple times in the past with good results. It was mostly a matter of being completely done and not willing to take a grinder and welder to anything on this. Plus i'd be reusing more of my old junk i have laying around with no guarantee as to seals etc.

    It worked out pretty well---but as with all these little things I had to mod it to make it work. I had to enlarge the bracket plate mount holes a hair over the 5/16ths bolt diameter this one used, original pattern was metric, smaller holes and a hair too close together.

    Another item to note is that they 1/2 scalers use hard line, so the master actually came with 1/8th fine NPT threading.

    The generic china mini banjo bolts are a 10mm coarse pitch, but i have some HEL 10mm 1.0 threaded banjos.

    Randy and i both agreed that i'd be able to get away with retapping the 1/8th to the 10mm 1.0 which i did. mounted it up banjo style and it leaked. didn't account for the light machine grooves on the master body. did a careful file session, tried again and got minor seepage. put some 180 grit down on my counter and flush sanded it against that and also sprayed a new copper washer with copper gasket sealer.

    Third time's the charm, no leaks. I also had to grind the lever down to match the shorter length of the clevis on the connection rod. When I shoot the buggy in some sunlight for the finished pics, I'll take some of the new setup. Meantime here comes 4 days of rain LOL
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