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Performance Machine leaking pistons?

  • Bikeguy51
    Bikeguy51
    3 months
    Hi guys,
    I have upgraded to a 6 piston performance machine front brake calliper,  it’s brand new, it came with pads etc already in so just had to bolt on and bleed and away I went, but it leaked? Seemed to be seeping from the top piston …I took the pistons out to have a look and noticed on the bottom of smaller piston some scoring or scratches ? Does anyone know what causes this? 
    Many thanks, cheers
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    Performance Machine leaking pistons?
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  • Hogey
    Hogey
    3 months
    i have fitted new seal kits never seen a piston like that . being new you should be send the caliper bake .
  • tussuck
    tussuck
    3 months
    No idea here, but if the scrapping is only on that flat surface then i would think its fine.  Its not like its a seal surface ect.  key would be to ensure the piston skirts and bores are all scratch free.  maybe a dud seal?  are you using the right fluid DOT4 vs. DOT5?
  • Hilly
    Hilly
    3 months
    Agree with Hogey, it should be warranty, as for the leak it's usually a damaged seal and or scored bore, could also be a casting flaw creating a bypass point but unlikely, that scratched up surface on the end of the piston while not ideal it would not cause the leak unless the scratches are also on the sealing surface, what caused it.... manufacturing stuff up of some sort, nothing you have done by bolting it on and bleeding it.
  • Bikeguy51
    Bikeguy51
    3 months
    Quoting tussuck on 31 Jul 2024 07:34 AM

    No idea here, but if the scrapping is only on that flat surface then i would think its fine.  Its not like its a seal surface ect.  key would be to ensure the piston skirts and bores are all scratch free.  maybe a dud seal?  are you using the right fluid DOT4 vs. DOT5?

    Thanks Guys, appreciated, I use dot 4 as that’s what my master cylinder says on the top, plus I checked with the shop when I picked up the brake…
    I agree with you about it being warranty, waiting to see if the shop will honour, they have sent away the pictures etc to performance machine
  • beaglebasher
    beaglebasher
    3 months
    Looks like the quality control bloke was on holiday.
    If the underside of the piston is as fucked up as it looks like in the pics you would have to think there would be microscopic cracks /scratches  in the metal that could travel to the circumference of the piston.
    That would cause a leak. 
    Welcome to the forum number 51.   Send it back.
  • Bikeguy51
    Bikeguy51
    3 months
    Quoting beaglebasher on 31 Jul 2024 10:34 AMedited: 31 Jul 2024 06:01 PM

    Looks like the quality control bloke was on holiday.

    If the underside of the piston is as fucked up as it looks like in the pics you would have to think there would be microscopic cracks /scratches  in the metal that could travel to the circumference of the piston.
    That would cause a leak. 
    Welcome to the forum number 51.   Send it back.

    Thanks beaglebasher, makes sense what you are saying, i was thinking along those lines too so I had a really good look at the piston sleeve inside the calliper and in particular at the bottom of the smaller piston pot, i cannot find anything looking even remotely like the scoring/scratches i have found on the bottom of the small piston? got me buggered, will send it all back and wait for them to say " must have happened during install" 
  • Far Canal
    Far Canal
    3 months
    Hi Bikeguy51.
    Sorry to be the bloke who has to break the ugly truth to you.
    In my opinion these PM 6 piston callipers are fucken useless and there is something inherently wrong with the design of them.
    I bought set of them many years ago to replace the standard HD callipers on a FXST after installing a stage 4 motor kit.
    Found them to be be no better than the standard HD 4 pot callipers. Had a bit of a whinge to the HD dealer I bought them from and they suggested I go for a larger PM brake rotor/disc (13 inch) which meant I'd need a different PM 6 piston calliper as well to suit the bigger rotor. So I bought the bigger rotor and suiting calliper and much to my dismay the set up was not really that much better than the stock Harley ones and my wallet was murdered.
    Ended up buying a 15 inch Arlen Ness rotor/disc and putting the stock HD calliper back on and it is a great set up, shits all over the pissy PM 6pot hunk of shit.
    I do believe the 4 piston PM callipers are good units but there is something (hydraulically wrong) that just does not work with the 6 piston progressive sized pots. Maybe they would work better with a different sized master cylinder but they are sold as compatible with stock ones and should therefore work with them.
    I could go on and on venting spleen at these callipers like the stupidly small bleeding screw etc, etc but it might not make you feel much better about your stiuation.


  • Hilly
    Hilly
    3 months
    FC is not the first person I have seen saying this about the 6 pot calipers, I have no personal experience with them and after that there is no chance I'll ever buy one either.
  • Hogey
    Hogey
    3 months
    Funny this topic about the PM 6 i fitted one to a customers bike and is not happy with it is used on a stock Fxst. i have Hawg Halter 6 and they use same pad size  only diff i have a HD Sunnen floating disc cant fault mine heaps of stopping power , My 2c
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