Author Topic: 1920s/30s carbs  (Read 1236 times)

Offline geoff.godwin

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1920s/30s carbs
« on: December 19, 2023, 08:28:02 PM »
Back in the 20s and 30s  some bikes had the amal or amac mounted with the body and throttle slide horizontal . was this just to save height ? and were the carbs specials or just the usual with different float bowls .Geoff

Offline Rex

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Re: 1920s/30s carbs
« Reply #1 on: December 19, 2023, 09:41:57 PM »
The usual with different float bowls.
Usually done when the engine design was for a relatively high-mounted mag.

Offline R

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Re: 1920s/30s carbs
« Reply #2 on: December 20, 2023, 09:35:23 PM »
And they couldn't mount the tank any higher.  !

Careful attention must be paid to float/fuel height.
Or flooding and woeful fuel consumption will be the bane of your life...

Offline cardan

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Re: 1920s/30s carbs
« Reply #3 on: December 20, 2023, 09:54:15 PM »
I've often wondered how the fuel level thing worked on the horizontal-bodied carbs.

In 1933 (a year of disasters) Douglas used a down-draft version of the horizontal-bodied AMAL on their big twins. Perhaps lucky they didn't make many bikes that year as I suppose flooding would literally fill the engine with fuel!

Leon

Offline john.k

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Re: 1920s/30s carbs
« Reply #4 on: December 21, 2023, 02:04:00 AM »
I asked about how this worked once before ,no one knew .........you often (or used to) see the side mount float bowls on ebay ........still do ocassionally for stupid money.......I wanted to use one on a JAP single .........Triumph singles of the mid 30s always had sideways Amals ,and a few others did use them sometimes.

Offline 33d6

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Re: 1920s/30s carbs
« Reply #5 on: December 21, 2023, 02:51:26 AM »
You donít appreciate how much gravity and vibration assist throttle slide return until youíve messed about with a horizontal carb.
My experience dates back to the 50ís and 60ís when bikes of the horizontal carb era were just old bangers. Not vintage, not ďclassic ď but just old rigid frame bikes that girls wouldnít ride on.  But they were cheap, very, very cheap, so appropriate for a rather sad element of riders with delusions about their ability.
When worn the slides would stick remarkably easily anD frighten the life out of you. A new slide with sharp edges stuck even easier. New carb bodies were near impossible for a gormless yoof to find and out of my price range anyway plus body resleeving was years in the future.
I quickly learned to avoid them.

Offline R

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Re: 1920s/30s carbs
« Reply #6 on: December 21, 2023, 03:00:17 AM »
I'm in the throes of fitting what appears to be a brand new brass one to a 30's RE
An Allparts one, if I'm not mistaken.

Note the black line for the fuel level.
Dunno where I found that info, but seems suitable for the task ?

As a backup plan B, have a looong inlet spacer that would suit a conventional upright amal,
and thus avoid the magdyno (which was optional on some models)


Offline R

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Re: 1920s/30s carbs
« Reply #7 on: December 21, 2023, 03:03:58 AM »
The body and floatbowl appear new, the fittings are not.
Presumably transferred from the old one ?

Offline geoff.godwin

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Re: 1920s/30s carbs
« Reply #8 on: December 21, 2023, 08:44:55 AM »
The reason I first asked about horizontal carbs was conflicting information about mounting the amac on my 29 Enfield . The old copy sales stuff shows a normal mount , but most of the images on the net show horizontal mount. I think now that if a bike was ordered with lights a longer inlet tract was used [to clear the magdyno] .My bike has the longer tract so room is not an issue. I am still having aggro trying to get it to start and run for more than a short while , the little sod seems to need to be flooded in order to keep running . I am starting to appreciate how easy electric starters are !! With a sore leg  Geoff

Offline R

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Re: 1920s/30s carbs
« Reply #9 on: December 21, 2023, 09:17:26 AM »
the little sod seems to need to be flooded in order to keep running .

That might suggest the fuel level is a bit low ?
A cold start may need some choke however - hence the tickling.
But obviously that need should go away once warmed up.

In the 1930s, if you ordered your new (Deluxe) Enfield with a magdyno, you also got tubular steel forks. !
Amals appear to have made upright carbs with suitably long necks, at some point.

Offline john.k

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Re: 1920s/30s carbs
« Reply #10 on: January 13, 2024, 07:07:44 AM »
The commonest long flange mount Amal s come off Ariel VAs and VBs ......other makes seem to have economized by using a clip mount on a long steel intake...........in some ways the clip mount is better ,as oaf with spanner (one only) cant distort the flange............i had a good look at sideways carbs ,and prewar ones that were outside vented seem even more unlikely for sideways ......yet they were used sideways..............anyhoo,as the OP says ,the fuel level is somewhat lower than the jets ,and difficult starting .....or rather a different technique ...the result..............It seems the choke operating properly would be essential for a start ..................I needed one of these for a JAP some time ago,but the spillage of flammables was disconcerting ,and I went with a long steel intake instead..

Offline 33d6

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Re: 1920s/30s carbs
« Reply #11 on: January 14, 2024, 12:45:06 AM »
According to their literature Amal didnít approve of using a clip fitting to attach their carbs as they believed them prone to air leaks.
As Villiers used nothing but a clip fitting on their motorcycle carbs Iím inclined to understand why, particularly on aluminium inlet manifolds. Routine carb removal for maintenance wears away the aluminium surprisingly quickly. Eventually they changed to bronze manifolds.
Itís weird the odd trivia you learn when you play with old bikes isnít it.