Anybody ever taken the head off a Joplin?

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  • Anybody ever taken the head off a Joplin?
  • Premier Icon wwaswas
    Subscriber

    how to grip the post,

    In the frame with a seatclamp?

    dvatcmark
    Member

    Sorry should have said that’s what I’m going to try first, if that fails I’m not sure what else to try.

    The drawing details the head as being torqued to 55Nm, I’n not a mechanical engineer so I’m not sure if a seat clamp will hold it

    Premier Icon wwaswas
    Subscriber

    I’ve always wrapped mine in lots of old inner tube and clamped them ‘lengthways’ in the jaws of a vice so the pressure’s spread over a wide area.

    dvatcmark
    Member

    Good idea, my old man has a 6 inch vice too

    hamishthecat
    Member

    The bit inside with the two holes for unscrewing it shouldn’t be in very tight – it’s only alloy and I’d have thought you’d rip the metal before bending the prongs on a steel tool. If you can’t get the head off you could try again with a 16mm socket ground down with an angle grinder and finished off with a file to leave two prongs.

    I think you’ll wreck the post part trying to grip the base and turn the head but you could make up a grip with a block of wood bored undersize for the post diameter and then sawn in half across the hole so you can put them in a vice and grip the post between the halves of wood.

    EDIT: 55Nm is quite a lot and i reckon would require you to crush the post tube or strain the guide blocks if you try to hold it in flat jaws.

    dvatcmark
    Member

    It might have been that the grade of steel on the Wilko’s drill bit I used was poor but the prongs both bent and then snapped after I straightened them.

    The socket idea is another possibility, I’ve seen differing measurements for the prongs though, some detail them as being 19.8mm centers, have you made a tool yourself?

    hamishthecat
    Member

    Yep – I’m pretty sure it was a 16mm socket which I ground down to leave two c.0.5mm prongs about 2mm high. someone on here recommended the boring bit tool and I think that was 16mm. The socket works well because you can use an extension bar and the socket itself sits flat on the part you need to unscrew. I can measure tonight and confirm.

    dvatcmark
    Member

    If you could please, that’s be great

    dvatcmark
    Member

    As title really, my Joplin is leaking air on the poker seal so it needs a seal change or just good clean, but this means removing the seal head….

    I’m not going to invest any more in it as it’s been back to 2pure a number of times and the warranty has now expired so I’ going to have a go myself rather than selling it for spares. I’ve tried making a tool to remove the seal head using a flat drill bit (per thread on here) and it’s not strong enough to undo the head.

    So my next idea is to unscrew the head of the post, as looking at the exploded diagram it’s just on a thread with green loctite to hold it in place and this will give me access to the poker seal.
    Obviously I’ll empty the oil and de-pressurize before trying to get the head off, but before I start has anybody tried it before and can offer any tips?

    The only problem I see really is how to grip the post, Ill remove the seat clamp and pass a bar through the head to turn it.

    I dont know if this helps you but this is how I repaired a leaking push rod o-ring (years back)?

    http://singletrackworld.com/forum/topic/diy-joplin-top-seal-head-removal-fitting-tool

    hamishthecat
    Member

    ^^^ this is the post I was trying to find – confirms 16mm.

    I used a 9/16 socket ground down to make two very small prongs on the inner rim of the socket giving a 16mm separation. I can’t link to my Flickr account properly but socket is shown.
    here (mechanical enginers look away now)

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