Author Topic: How not to do it! - finding floatchambers for Amac on my 2 3/4 HP  (Read 7293 times)

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Offline pvn06

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Although my 2 3/4HP restoration basket case looks to have the correct early Amac carb (notice it has a clamp style fixing to the inlet manifold, which I think is correct for a 'teens  2 3/4), it's float chamber had been fitted with a later Amal small diameter float chamber cap.  Therefore, for the last month or so I had been keeping a careful vigil on ebay.  Added to this, my own Amac carb float chamber was missing the internal float and float needle.

About 3 weeks ago I spotted a very nice condition Amac float chamber and was (as normal) sat there poised in the last 10 seconds of the auction and was successful in winning it.  When it arrived I was over the moon - as it was in even better condition than the ebay photos indicated.  However, once out in the workshop, the situation did not look so rosy - the float chamber was slightly bigger than the Douglas version, the cap would not fit, the float would not fit in and the mount to the main carb was different - with the original Douglas type having a flange and an internal taper that the bigger float chamber did not have!
Just goes to show how easy it is to get caught out . . . I though it looked pretty close in the photos, shows what I know!

Anyway, as it was so nice, initially I thought I might do my normal bit - and make it fit! (i.e. machine the mounting to fit the earlier carb) - but within a day or so I found myself running my normal search trawl's on Ebay and was very surprised to within a week or so find the float chamber you see in the accompanying photos.  There was not too much interest until the last few seconds (that's not unusual though on ebay) - but as a coincidence I ended up in small last seconds battle and paid almost exactly the same amount as the other one.  However, in this case I seem to have got it right - as this one is the same type as my original - but has a complete and good condition Amac floatchamber top and tickler, as well as the float and float needle inside.
Again, on arrival it was a quick visit to the workshop, but this time I was not disappointed and it is a perfect fit.

Although a little bit wiser (or as Churchill would have said - not wiser, but better informed!) I am not disappointed by having paid twice the amount I intended - I have learnt a bit from it . . . and my spare engine is fitted with a later small bore Amal.  As I was considering for the future working out how to turn this SV into a replica of the first pre-Kaiser OHV, a slightly bigger Amac may be a consideration . . . and also it is very pretty!

As a final point of interest - while photographing the original Amac fitted to my bike for this article, I noticed traces of dark army green paint on the body and original floatchamber - leading me to believe the carb and inlet tract may be from a WW1 WD bike . . . what a lovely little time capsule!

More soon,
Paul
www.racingvincent.co.uk

Offline pvn06

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and now photos:

Offline pvn06

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and a few more:

Offline cardan

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Hi Paul,

Welcome to the world of (truly) vintage motorcycles!

By chance I spent yesterday afternoon in the shed sorting out my box of AMAC carburettors, and I can confirm that there are many different fittings for the flat-chamber connection (four I can think of), as well as different float bowl sizes. The earliest AMAC I have is a 1909 model (on my water-cooled Lewis), and the merger with B&B and Binks to form AMAL occurred, rather gradually, in the period 1928-1930. Plenty of traps for the unwary over 20 years of AMAC carbies.

Before I get bombarded, the AMAC box has been drained dry of 2 3/4 Douglas carbs. However there is one very small AMAC float bowl, but to my eye it looks even smaller than required by Douglas. It might be veteran Douglas - perhaps the first year of the AMAC, 1913?

Cheers

Leon

Offline eddie

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The carby on the engine looks to have been fitted with the tickler from an Amal Monobloc carb!

  Eddie.

Offline pvn06

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Hi Leon,
Yes - always learning . . . that is what I love about working on old bikes, as you move into a new area you find out new things and you start to unravel a little bit about that period of time . . . I am starting to learn a little bit more about Amac's now!
I will leave the carb's there for now - I will come back and strip the very original looking main body sometime in the future  . . . and no doubt will find all things I need to do and learn then!  Incidentally . . . I have a tin of very early Amal jets and bits (from my old friend Titch Allen), which I have always thought of as - from old carbs that are older than I will ever need or own (most of my rare carbs are racing TT's/RN's or similar from the 30's-50's) - but having revisited that tin recently  . . . I have found it is still too modern for the Douglas! (probably late '20s)
Moving on . . .
Paul
www.RacingVincent.co.uk

ps - thanks as well Eddie, although now you have taken the edge off! . . . now you mention it, that tickler does look like a later one .  .. perhaps I will just have to machine a proper looking one! (shall have to find a photo somewhere)

Offline cardan

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I found these photos on my computer, showing a "typical" veteran Douglas-AMAC (with the exhaust-gas heater), and a "typical" 1920s model. AMAC literature suggests that the veteran version would have been current c1914-1919, replaced by the later type 1920-1925. There were variations on each pattern.

The method of attachment of the fuel bowl is one of the points of difference.

Leon

Offline Domas

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Done.
« Last Edit: 10 Aug 2019 at 11:00 by Domas »