what size are suzuki dr400 almunimum gascap threads

Discussion in 'The Garage' started by meijer's trails, Aug 13, 2013.

  1. meijer's trails

    meijer's trails Been here awhile

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    I have 3 thread peaks. Across 5mm exactly. Like first peak at 0, second 2.5,3rd at 5 mm.

    Is that a 2.5mm pitch?

    I think its a 50mm dia
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  2. stainlesscycle

    stainlesscycle Long timer

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    correct. metric pitch is measured distance between peaks in mm. also, if you have a thread that is metric, but too fine to measure easily peak to peak, measure how many peaks in 10mm, and divide by that amount. i.e. your threads 10mm = 4 peaks, 10/4=2.5
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  3. meijer's trails

    meijer's trails Been here awhile

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    Thanks stainless!!

    Any ideas about thread diameter its either 49 50 or 51 on the 1980 Suzuki dr400

    I don't have appropriate wires for thread measurement
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  4. ohgood

    ohgood Just givver tha berries !!!

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  5. stainlesscycle

    stainlesscycle Long timer

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    i have no idea as to the diameter. i could only guess 50, as 49 and 51 would be strange numbers for metric stuff - usually goes by even numbers in thread diameter (except the dreaded 7mm)
    #5
  6. meijer's trails

    meijer's trails Been here awhile

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    Stainless, did you see that puch mx175 on eBay in Lansing mi? Its right b me.if you need me pick that up for you.

    Anyway, Is there any chance that the dr400 could have an s.a.e. gascap thread?
    #6
  7. Twin-shocker

    Twin-shocker Long timer

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    Threads in tanks are often buttress type. This is pretty much always the case if a plastic fuel cap is used on alloy tank.
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  8. stainlesscycle

    stainlesscycle Long timer

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    i saw it - i have enough of them at the moment :D


    could be sae, could be national pipe thread. who knows.
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  9. meijer's trails

    meijer's trails Been here awhile

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    Hmmmm. Butress-type threads... googling now.
    Never heard of those.
    The Chinese ano.alum. cap I ordered has thick threads similar to acme threads from a vise. Is that a buttress?
    #9
  10. Twin-shocker

    Twin-shocker Long timer

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    Buttress thread is similar appearance to acme. I wonder whats the problem here? Do you want to have a cap made to fit your tank?
    #10
  11. meijer's trails

    meijer's trails Been here awhile

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    The original plastic cap is so cross threaded its basically destroyed. So crossthreaded i cant even get it to start onto the aluminum threads. So I was trying to switch to an aluminum cap for aluminum threads.

    Just now Im Considering heating the threads and melting a new start into the plastic cap.

    I'm also conidering a castable polyurethane into a new plastic cap.

    Aluminum would be best though
    #11
  12. Twin-shocker

    Twin-shocker Long timer

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    Aluminium into aluminium threads never tends to work that well, but I guess you could almost certainly find a cap intended for an MX bike, to fit your tank.
    #12
  13. meijer's trails

    meijer's trails Been here awhile

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    [​IMG][​IMG][​IMG]

    I fnlly got an accurate measurement. 2.096"/53.25mm dia.
    The threads seem to be normal 60deg type straight, not tapered.

    I can't quite make out the pitch though. It seems so close to 2.5mm or 10tpi
    I can't find a standard thread of that size listed in any tables
    Any ideas?
    #13
  14. stainlesscycle

    stainlesscycle Long timer

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    is there a mc junk yard near ya? i'd be bringing my tank over there and checking caps. i'm assuming there are no dr400 caps anywhere to be found?
    #14
  15. meijer's trails

    meijer's trails Been here awhile

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    Guys, the 10tpi pitch guage really matches well(with just a tiny sliver of light equidistant at each thread)
    The pitch gauge seems to have ever so slightly deeper threads than the aluminum filler neck

    Ideas?.
    #15
  16. Twin-shocker

    Twin-shocker Long timer

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  17. stainlesscycle

    stainlesscycle Long timer

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    dr, not drz. drz is plastic tank. maybe an sp series tank cap would work, but just guessing...
    #17
  18. Twin-shocker

    Twin-shocker Long timer

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    If a cap proves impossible, then maybe an idea to get an alloy cap and neck from Ebay and get that welded into your tank?
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  19. broncobowsher

    broncobowsher Long timer

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    Without doing any real research, have you tried a 2" PVC threaded cap?

    Our Nissan forklift at work has a plastic PVC home depot plumbing section cap on it to cover the gas filler. (yes, it is an old bastard POS) I was surprised it fit, especially being a japan built piece of equipment. Screws right on and doesn't look like anyone has monkeyed with any of the threads.

    Might be something to check.
    #19
  20. Z50R

    Z50R Not lost yet

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    Friend with a lathe? You have access to fancy measurement techniques, you have to know a friend of a friend who can make a gas cap.
    #20