Topic: Koban Mixture Needle – Antique Outboard Motor Club,Inc

This topic has 10 replies, 5 voices, and was last updated 7 years, 10 months ago by Monte NZ.

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November 5, 2016 at 1:26 am #5635
Mumbles
Participant
The original mixture needle in my Koban doesn’t give me much to go on for making a replacement. Just wondering if anyone can post a closeup photo of theirs showing the taper and its length. Thanks in advance! ☺

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November 5, 2016 at 2:43 am #47027
pm-t2
Participant
Canada Member - 2 Years
I will get one of mine out tomorrow and take a picture.

PM T2
November 6, 2016 at 2:18 am #47047
pm-t2
Participant
Canada Member - 2 Years
The length of the non-threaded section is .500, with the tapered part comprising half of that (0.250" length of taper), and it looks to be a 10 degree taper. The non-tapered section of the shank is 0.170" diameter.

Hope it helps.

Best,
PM T2
November 6, 2016 at 2:36 am #47050
Mumbles
Participant
Thanks Chris! 10 degrees sounds about right as that is the same taper on some other ones I’ve made. It’s those dimensions I really needed! 😀
November 6, 2016 at 4:34 am #47056
hotrod
Participant
How many carburetors did Koban use ? In the 4 catalogs I’ve seen, all models use the Koban Non-sensitive Economy carburetor, including the pre-1920 Model C (which is also shown as being sold only with an airfloat feed carburetor in one of the catalogs). I assume the mixture needles would be different on these 2 carbs.
November 6, 2016 at 5:21 am #47059
Mumbles
Participant
The photos at Jack Craibs site, http://www.caille.8m.com/rowboat/Koban/koban-index.html show the C with a different mixer than the others so there must have been at least two variations. The 1915 C poppet valve is horizontal while the other ones are vertical. The motor I’m working on is a ’21 H so if the dimensions are different than the ones given, I should be able to figure it out soon enough. Good point!

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November 6, 2016 at 1:06 pm #47069
pm-t2
Participant
Canada Member - 2 Years
On the green Koban (I doubt the green paint is correct) you can see the mixer known as the "Air-Flow" or "Air-Float" carburetor. Notice the finned cylinder heads, which were only used on 1914 models. For 1915, they changed to a domed cylinder head that did not have any lettering on it.

This style of mixer was more or less discontinued after 1915, and the mixer with the "KOBAN" cap was standard for the duration of the Koban production.

Probably safe to say that from what I’ve seen, one mixer needle fits all on Koban’s built with the "economy" carburetor.

Hope this helps.

Best,
PM T2
November 8, 2016 at 12:10 am #47139
Mumbles
Participant
The new replacement needle is finished but I did cut the tip at 20° instead of 10° as at 10°, it was too pointy and poked thru the orifice keeping the valve off its seat. 15 might be the magic number but we’ll see. A light press fit with a dab of solder should keep the original brass knob on the new needle. One more issue solved and a step closer to ‘The Big Day‘!
November 8, 2016 at 12:12 am #47140
chris-p
Participant
Fantastic. I love seeing what some of you guys are able to accomplish!
November 8, 2016 at 12:39 am #47141
pm-t2
Participant
Canada Member - 2 Years
Nice job Jim. the 20 degree will work, it really should only make a very slight difference in how far out you turn the needle to get it running its best.
If I ‘member correctly, that’s a fairly coarse thread, (24 TPI, I sorta think) so I’d bet that anything more than 5/8ths of a turn out is going to be excessive.

PS – FWIW i try to silver solder the knob to the new shank, but I ‘spose ya don’t really hafta…..

Best,’
PM T2
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