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Help 6mm Helicoil tap size

Discussion in 'Maintenance' started by Andych, Jun 12, 2019.

  1. Andych

    Andych Well-Known Member Premium Member

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    I need to repair both threads in the main body of the FZR250 Master Cylinder and I think they are 6mm.
    Is anyone able to measure them to confirm they are 6mm and does anyone have a 6mm Helicoill kit that can tell me what Tap size it is.. just that the bosses in the Master Cylinder are not too large.. I just want to make sure it will work.
    I do have a repair lit and new screws coming but it would be good to know before they get here I guess.
     
  2. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Is that for a 3LN1 Brake Master the 2x bar clamp bolt's ? My 3LN3 use's M6 bolt's
    Helicoil use a non standard tap it's an STI tap (Screw Thread Insert)
    I'm pretty sure you drill it out with a 6.2mm drill bit then run the STI tap trough the hole to prep it for the thread insert
     
  3. Andych

    Andych Well-Known Member Premium Member

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    No, this is for the Countersink screws that hold the lid on.
    It was a guess they are M6, they could well be M4.
    I am not worried about the tap other than making sure it isn’t too large for the boss size in the main body of the master cylinder.


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  4. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    Sorry can't help with size mine has the remote reservoir, but i'm guessing M4 thread, 8mm or 10mm long
    @GreyImport might have one apart he can check for you

    The Helicoil / Recoil tap's aren't normal tap's as they need to have the same external pitch as the inside of the insert so each coil of the insert is supported
     
  5. Andych

    Andych Well-Known Member Premium Member

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    I might wait until the new screws turn up and I can measure them up.
    I looked at Timeserts too but they are only a mild steel insert and given that it will be out in the weather etc steel screws and steel insert probably won’t work.


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  6. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    An M6 thread has a 1mm pitch, so a tap for the helicoil would have to be a M7x1mm I would think.
     
  7. Andych

    Andych Well-Known Member Premium Member

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    Thanks @Murdo
    I will take a pic of the MC when I get home so people can see why I am asking.

    I need to look at the service manual to see if they list the lid screw sizes.


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  8. Andych

    Andych Well-Known Member Premium Member

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    Searched through the manual and it turns out the screws are M5 x .8, at least they are for the SRX so you would think they would be the same for the FZR250..... time to do some checking on parts lists.
     
  9. my67xr

    my67xr Bike Enthusiast Staff Member Premium Member Contributing Member

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    @Murdo the M6 STI tap is closer to M8 but it's still different, i'll try and find my M6 Helicoil/Recoil kit
     
  10. Andych

    Andych Well-Known Member Premium Member

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    No need for now... they are an M5 screw anyway... hopefully there will be enough meat in the bosses.. .didnt get a chance to get a pic today.. work has been going nuts... apparently there is a drought.. Numpties here in Sydney are only just realising that fact..
     

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