Clutch Master Cylinder ID

Discussion in 'Trials' started by mayoisnasty, May 14, 2020.

  1. mayoisnasty

    mayoisnasty trials wannabe

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    I'm looking to rebuild my master cylinder, but I'm having trouble finding the correct kit. The bike is a 2013 GG TXT Racing. The parts diagram from GG shows part BR46000R3009. On the bottom of the part itself, there is a white stamp reading "BK-0053-C". The MC cover is of no help, as it's aftermarket S3 bling.

    On the sites I'm searching, the kit I find shows for a master cylinder that has covers that are parallelogram-shaped. Mine are shaped like AJP covers...so I am really confused. Any input would be appreciated!

    Attached Files:

    #1
  2. lineaway

    lineaway Long timer

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    Showing an after market cover does nothing. Why not the whole m/c. Good chance it is AJP as several went back to them as 2011 _ 2013 sucked.
    #2
  3. Hyperbolic22

    Hyperbolic22 Been here awhile

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    If it's the Braktec MC repair kit that you're after, I have one that I can send you. I bought it for my 2014, but ended up just sending my MC to Motobene to repair instead.
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  4. mayoisnasty

    mayoisnasty trials wannabe

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    My apologies. It was late.. low light and a $20 cell phone doesn't provide very good pictures. I thought the shape may confirm the manufacturer anyway. The B and BT parts numbers kept making me think is was braktec. Please excuse my ignorance on the subject.
    20200515_065022.jpg
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  5. lineaway

    lineaway Long timer

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    No worries, we were all confused when they went to Formula brakes and they might not last the first ride around the block.:imaposer Most riders would get new bikes, swapped the ajp`s to the new bike. Then sell the old bike with new master cylinders that were junk. A couple of weird years for the riders and manufacturers.
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  6. Cascao

    Cascao Been here awhile

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    This one is AJP small master cylinder.
    One more thing you have to look is if you're using DOT or mineral hydraulic fluid.
    Mineral uses a green ruber (gasket) under cover. DOT uses a black rubber.
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  7. mayoisnasty

    mayoisnasty trials wannabe

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    Thank you. That answers another question I had. Good to know about the gasket colors. I thought I was screwed since this had an aftermarket cover.
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  8. Cascao

    Cascao Been here awhile

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    another tip:
    DOT fluid become white imediatelly when mixed with water.
    Mineral oil doesn't mix with water.
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  9. motobene

    motobene Motoing for 49 years Supporter

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    A bit more info.

    There was a general change in the master cylinder diameter on trials bikes years back. Early hydraulics were based on 11mm master cylinders. I don't know if any Brembo master cylinders were used for a time at 10mm like on the bigger bikes, but the majority now are 9.5mm. That's good for more 'mechanical' advantage on smallish brakes and clutch slave cylinders of trials bikes. The very low displaced volume can make bleeding a real B, however.

    AJP got taken out in market contraction and Braktech gobbled them up and continued to produce the older design which curiously became more preferred on the clutch side.

    This pistons are often hard coated aluminum and very enduring, and though they can last decades you end up replacing them because the seals are very small and some would damage them trying to get them onto the piston. I do it with dental tools under a microscope.

    The seals look the same but the materials are different for the glycol (alcohol)-based DOT fluids, 3, 4, and 5.1, and the mineral (petroleum) based oil still used with clutches. I'm not sure why mineral oil is used in some clutches, but it would be simpler if the clutch used glycol fluids like the bigger bikes. The 10mm Brembo clutch master cylinders on KTM, Husqvarna, Beta, etc, are DOT 4 based.

    Make sure to use the very light mineral oil in the clutch master cylinder that is for motos or bicycles. I have used Magura blood (reddish), and Magura royal blood (bluish), though the seems to have gone poof in the market. Unscented drug store mineral oil (intestinal lubricant) is glue thick compared to the more expensive stuff.

    Nice trick for using water to check for glycol fluids Cascao! I rely on smell, but sometimes doubt my nose.
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  10. mayoisnasty

    mayoisnasty trials wannabe

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    Thanks for the info motobene. I ran across an old thread of yours on the subject of mineral oils. I began searching for some Magura...seems royal blood is plentiful (although expensive) on Amazon.
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  11. jonnyc21

    jonnyc21 Trials Ninja

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    I find it interesting that there are so many clutch systems with the mineral oil rather then DOT based, my Montesa is DOT for both clutch and brake, if I remember correctly, and I found it strange that the Gas Gas wasn’t.

    come to think of it I seem to recall my daughters old Beta 80 is DOT for both as well... will double check this later. (Edit: yes, Montesa and our Beta 80 use DOT 4)
    #11
  12. mung

    mung Long timer

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    Another option is to use DOT 5 silicone fluid. It is compatible with all moto hydraulic systems. All my bikes use DOT 5.
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  13. motobene

    motobene Motoing for 49 years Supporter

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    I had some brilliant idea once that the reason for mineral oil in the GasGas clutch was because the top hat (the cylinder of the slave cylinder) is bathed in... mineral oil (gearbox oil), and some cross talk via o-rings weep between glycol-based DOT4 and mineral oils was not desired.

    So too potential deliterious interactions with externally mounted slave cylinder piston seals and transmission fluid where the clutch rod isn't sealed, and the transmission oil seal is a face seal o-ring on the slave cylinder.

    It's the only reason I could come up with as to why complicate things with mineral oil clutches because you know a bunch of folks have dropped glycol fluids into mineral oil clutch reservoirs. Oops!
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  14. motobene

    motobene Motoing for 49 years Supporter

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    Lots of opinions on DOT 5 (silicone). I've never worked hard enough at cleaning glycol-based fluids out of a system to convert to DOT 5. I find it good enough to keep DOT 3 and 4 from getting dark and gross, and that doesn't take a lot of effort. The simplest thing is mopping out reservoirs with paper towel and tossing in fresh stuff, then letting that fresh stuff replace what's below by gravity bleed. Or on new systems force bleeding fresh stuff from the bottom up.

    The follwing video is interesting because it talks about the role of water and the creation of DOT 5 by military demand. Hadn't thought about the plus side of hydrophillic fluids until watching it.



    If you want a chuckle on DOT 5 opinions, listen to Dr. Crusty:

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