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Old 06-17-2013, 08:54 AM   #1
Ben Carufel OP
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Karcoma Petcock Straws -- How Are They Held In?

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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Old 06-17-2013, 09:02 AM   #2
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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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Old 06-17-2013, 09:04 AM   #3
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Quote:
Originally Posted by disston View Post
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.
That's what I was thinking...might be time for some gentle Dremel work.
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Old 06-17-2013, 11:16 AM   #4
Stan_R80/7
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Capital cycle sells replacement straws:http://secure.capitalcycle.com/STRAW...+12+2+302+045/. I have used Permatex Aviation form-a-gasket No. 3 sealant on the straws, which seemed to work ok. In the end, I bought new Karcoma petcocks from Motobins. Good luck!


Stan_R80/7 screwed with this post 06-17-2013 at 11:34 AM Reason: changed material used to seal straws
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Old 06-17-2013, 11:37 AM   #5
rufusswan
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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.
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Old 06-17-2013, 12:48 PM   #6
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Quote:
Originally Posted by Ben Carufel View Post
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!
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.
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Old 06-17-2013, 01:23 PM   #7
blaine.hale
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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.
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Old 06-17-2013, 01:26 PM   #8
disston
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Plaka,

You say "Brass but never Copper". Why is that?
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Old 06-17-2013, 01:39 PM   #9
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Originally Posted by disston View Post
Plaka,

You say "Brass but never Copper". Why is that?
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?
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Old 06-17-2013, 01:49 PM   #10
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Quote:
Originally Posted by blaine.hale View Post
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.
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.
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Old 06-17-2013, 02:16 PM   #11
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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?
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Old 06-17-2013, 03:33 PM   #12
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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.

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.

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Old 06-17-2013, 04:09 PM   #13
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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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Old 06-17-2013, 04:20 PM   #14
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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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Old 06-17-2013, 04:29 PM   #15
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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.
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