Karcoma Petcock Straws -- How Are They Held In?

Discussion in 'Airheads' started by Ben Carufel, Jun 17, 2013.

  1. Ben Carufel

    Ben Carufel Boxer Addict

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    In my crazy quest to get the /6 up to my standards so that I can sell it (I have an expensive problem wherein I don't feel comfortable selling a bike that needs work), I decided to do a light rebuild of the petcocks. They were rebuilt maybe 5 years ago by a previous owner with new rubber bits, but he didn't do anything about the straws, all 4 of which were broken near the bases and clogged with crap.

    I need to replace the straws (will source some new copper piping from a hobby shop) but meantime, I need to figure out how to get the small parts of them which are still stuck in the petcocks, out. They almost feel glued in.

    Is it just corrosion of some sort holding them into the petcock, or am I up against some sort of actual adhesive?

    Thanks!
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  2. disston

    disston ShadeTreeExpert

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    I don't think the original straws were glued in but they could be glued now. Maybe you will have to drill the remnants out.
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  3. Ben Carufel

    Ben Carufel Boxer Addict

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    That's what I was thinking...might be time for some gentle Dremel work.
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  4. Stan_R80/7

    Stan_R80/7 Beastly Gnarly

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  5. rufusswan

    rufusswan Been here awhile

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    If you are getting some tubing from the hobby store, take the petcock with you. That way you'll get tubing before you drill the wrong size hole.
    #5
  6. Plaka

    Plaka Brevis illi vita est

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    Brass from the hobby store, never copper.

    Drill them. Spin the drill bit between your fingers. Put tape on it if you need to.

    Another trick is to find a bolt that fits into the stubs and very carefully super glue that into the stub. You really have to control the glue, for obvious reasons. Use gel type and have super glue solvent on hand. You can also use baking soda with the super glue. Experiment on a coke can bottom to see what that does.

    With the bolt grabbing the stub, try gentle turning and pulling. if it won't come, use the super glue solvent to remove bolt and go some other way.

    If you can get the stubs sawed off flush and nice and all, you can simply sleeve inside them with fresh tube---it's that thin. Then oversleeve your new pieces with the next size up to strengthen and bring the OD back to spec.

    Bed everything in blue locktite.

    You can sell anything in any condition..and even with the bad tubes it will run (so fit cheap fuel filters). Ethics only requires you to declare. In this case, that the petcock standpipes are damaged and need replaced. If that is a dealbreaker for sombody, they are not worthy of airhead ownership. And if they are going to rap...er...cafe it, they may not want that tank anyway.
    #6
  7. blaine.hale

    blaine.hale Long timer

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    I recall popping my old ones out (press fit) and pressing in new, brass tubing I picked up at the local Ace.

    I can't seem to do the same for my /5 Germas. I can't, for the life of me, pull them out or figure out if they actually are just tubes pressed in...my assumption is yes, but they sure are stubborn.
    #7
  8. disston

    disston ShadeTreeExpert

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    Plaka,

    You say "Brass but never Copper". Why is that?
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  9. Plaka

    Plaka Brevis illi vita est

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    Three reasons:

    1)Copper is a lot softer than brass. Typically small diameter copper tube (I have a lot) is fully annealed, you are supposed to bend it. Typical applications are water supplies to refrigerators, humidifiers, internals on refrigeration units, etc. Poor rigidity, undesirable for the application.

    2)Because it is soft the wall thickness is greater than hobby type brass tubing. So less flow for your OD...and that OD is determined.

    3) Only a few sizes are common, others are quite hard to find outside industrial circles. Most of those sizes are over 1/2". You can get hobby brass tube, full hard, in a whole rackful of sizes, each nesting closely in the next. Desirable to avoid things that are hard to find.

    Brass is a copper alloy..there are a number of them and typically hobby store tube is drawn and thus a suitable alloy for that. Likely lower sulfer than free machining brass and less copper than red brass. I'd say the alloy itself, v.s. copper, is a non issue.



    My usage of the word "never" indicates a desire to present a course of action that will yield the best results with the least grief.

    -------------------------------


    So what do you know about the main jet size increase on the US/Cdn. (known, possibly others) for the R100RS (and some others) in only '79 and '80?
    #9
  10. Plaka

    Plaka Brevis illi vita est

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    If you fasten a short piece of all thread into them (glues, lock tighting, soft solder), you can then set a socket over them, thread a nut onto the rod and you have a puller. Use a bolt instead of the all thread and put the socket on that first.

    Heat, heating cooling cycles (boiling water to freezer), etc.
    #10
  11. Ben Carufel

    Ben Carufel Boxer Addict

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    Update: I used a pick to carefully munch up the bottoms of the tubes, then a 5/32" drill bit to drill them out. The drill bit was only slightly (.03mm) larger than the old tubes.

    Am now headed to the hobby shop for some 5/32" BRASS tubing.

    While I've got your attentions, what's the favorite silicone grease to be used during rebuilding of the petcocks?
    #11
  12. disston

    disston ShadeTreeExpert

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    Thanks Plaka. I have now learned something new today, I think.

    My favorite Silicone grease is the one with Silicone in it. :lol3

    For most of our applications the stuff sold at the auto parts superstores is sufficient. I buy name brand products when I get something like that but there are some high tech things usually sold at the Marine Store, high tech stuff that cost more money to be sure. There are many choices on Ebay. This one is made by 3M for dielectric use. $20 for 8 oz plus another $9.00 for shipping. I'm sure this is good stuff but I don't think I would get a hard on from using it.

    [​IMG]
    #12
  13. Ben Carufel

    Ben Carufel Boxer Addict

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    Thanks disston. On my way to the auto parts store to drop off some used oil and pick up some silicone grease now.

    The 5/32 brass tubing fits perfectly with the holes I drilled. Nicely snug, it's definitely not coming out on its own. Since the holes are at a slight angle, I will need to put a slight bend into the taller tube.

    Does anyone happen to have a Karcoma petcock laying around to measure the length of the tubes when installed? I am curious to know how far each tube extends past the flat upper surface (end of threads) of the petcock.
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  14. disston

    disston ShadeTreeExpert

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    I have customized the tube lengths on mine. The short tube is only a quarter inch high and the long tube, I'm not too sure, but think about an inch and a half. This is too short for the long straw because I get max mileage before I switch to reserve but only have about ten miles in my reserve. Some day I'll correct this.

    Make your straws any length you like. The OEM had a much longer than needed short straw. I think the idea was that the tank could fill with peeling paint and water for ten years before there was ever a sign of a problem and ya know what? That's sometimes what we find in the bottom of tanks with stock straws in them. If you make the long straw too short you have a smaller reserve. Is all that clear? I think I got it right.
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  15. Ben Carufel

    Ben Carufel Boxer Addict

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    Also, my local dealer is reporting that the upper strainer (the long one which covers the two straws), part number 16 12 2 307 112, is NLA. Hucky's doesn't show it as such and Max lets me add it to my cart, but my local dealer says it's just not available any longer.
    #15
  16. Ben Carufel

    Ben Carufel Boxer Addict

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    Yep, all makes sense. I think I'll make the long straw about 1cm shorter than the strainer piece, and the short straw will protrude about 2cm from petcock.
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  17. Kanticoy

    Kanticoy Been here awhile

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    I use the strainer from capital cycle in mine. Works just fine and it's cheap.
    #17
  18. Plaka

    Plaka Brevis illi vita est

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    they should be about 1/8-3/16" below the top of the screens. the short (reserve) tube determines the residual 'crap catcher' gas left in the tank. Longer is good if you get a lot of bad gas but shorter makes tanks last longer (you know sooner if there is water in there.)

    I bought a 2 oz tube of silicone di-electric grease (Enchlin brand from NAPA) in my early 20's. Some 35 years later I have half left, and I use it a lot on multiple vehicles.. I also have a film canister of Dow product dipped out of a 5 gallon bucket of the stuff I saw while working for Rubbermaid. It was being used at the beginning of a run to lube up the big extrusion dies they use to blow their trash can liners. Seldom use it---sometimes on light bulbs.

    The little packets sold on the counter display at the auto parts place will last a couple years---squeeze it out into a small Altoids tin or something.

    I went to a Chinese funeral once--a gal who worked for me. Everyone tossed something into the grave that she might want in the afterlife. I tossed in a very nice bit of 3 axis CNC work she had done (she was a machinist)...something to show if she went looking for work.

    Disston is going past the grave with the better part of an enormous can of silicone grease...

    Hard tubing don't like being bent. I'd leave it if the screens fit OK.
    #18
  19. Ben Carufel

    Ben Carufel Boxer Addict

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    Thanks for all the info. Went to 2 different stores looking for silicone grease, then I remembered that I have a tube of Syl Glide in the toolbox. Duh, that's exactly what it is. That'll work.

    Think I'm just going to re-use my existing strainers. My dealer has the 16 12 1 240 060 "fiber gasket" for the top connections in stock for 99 cents apiece and the strainers are fine, if a little discolored (who cares?). Beats spending $10 apiece plus shipping on the nifty new ones with integrated aluminum gaskets (which are apparently now NLA).

    Oh, and the 12" of brass tubing was a whopping $1.27 at the hobby store. Dig it.
    #19
  20. disston

    disston ShadeTreeExpert

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    I resisted, didn't buy it. But I still have a fair amount of junk. Some how I think my collection of junk may pale compared to Plaka's.
    #20