AMAL JETS/SMALL DIAMETER HOLES

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... and what you drain off might mix nicely with Tonic Water

MichaelG.

I would not try it.

As a central nervous system depressant, ethanol is one of the most commonly consumed psychoactive drugs.^[26]

The amount of ethanol in the body is typically quantified by blood alcohol content (BAC), which is here taken as weight of ethanol per unit volume of blood. Small doses of ethanol, in general, produce euphoria and relaxation; people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. At higher dosages (BAC > 1 g/L), ethanol acts as a central nervous system depressant, producing at progressively higher dosages, impaired sensory and motor function, slowed cognition, stupefaction, unconsciousness, and possible death. Ethanol is commonly consumed as a recreational drug, especially while socializing, due to its psychoactive effects.

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Nor would I

[hence my use of the devilish smiley thing]

... But, neither would I pour petrol into a water container.

MichaelG.

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https://m.youtube.com/watch?v=0vxukHgmKQ4

https://www.norfolkfireservice.gov.uk/nfrs/images/files/EPUK%20Storing%20Petrol%20at%20Home%20leaflet.pdf

Edited By Michael Gilligan on 16/01/2017 23:41:01

Edited By Michael Gilligan on 16/01/2017 23:57:02

Bear in mind too that most carbutator problems are electrical. I'd bet two rabbit traps to the old black billy that if you get your New Imperials' magnetos professionally rebuilt so you have a good strong, reliable spark, you will find the old bangers will run much better on any jet that is close enough.

I've seen it happen over and over again on vintage Harleys and various Brit bikes over the years. Weak spark will appear for all the world like fueling problems. You stop on the side of the road, change jets and presto, it runs better -- because the maggie or the spark coil and the sparkplugs have cooled down. Then down the road it starts playing up again as the maggie or coil heats up so, hey, a bigger jet helped earlier, so lets stop and put the next bigger one in, and hey presto the bike runs better again -- because the maggie or coil has cooled off again. Then next time they roll the bike out of the shed and start it up from cold -- guess what, the jets are too big! Must be super sensitive to jet size! So down in jet size they go and all is good, until they get on the road and the maggie heats up ... repeat, repeat, repeat etc.

New coil (if used) plug leads, caps and plugs are essential too. Seen many vintage riders come to grief trying to run the original equipment for authenticity but as the insulation breaks down, inevitably, over time dramas ensue. Most of those guys thought it was fueling problems too and spent massive time tinkering with carbs, cleaning gunge out of tanks, sealing manifolds etc etc only to find it all cleared up with a good ignition system. It took one old guy I know , a lifelong Harley expert, engineer, former beach racer etc,  about 10 years to give up on the fuel system of his WLA  and fit a new coil and leads. Guess what happened to his carb problems instantly?

Edited By Hopper on 16/01/2017 23:47:38

Edited By Hopper on 16/01/2017 23:54:59

Hopper, what you say about electrical problems is absolutely correct, personally I don't contemplate doing a restoration without getting the electricals renovated. Seen too many people on rallies with phoney carb problems

In this case however there is a genuine problem. Amal literature on lightweight carbs is very poor, often misleading and in this case just plain wrong. The carbs are extremely simple (no needle. Binks style) so tuning problems usually boil down to the fitting of incorrect parts or bodging, since the time they were made in the 1930's.

At this point in time the only aspect we are completely sure of is jet aperture, we are not even sure what overall lengths the jets should be. Reason is that AMAL made many types of small carb and parts often interchange but don't work properly in their new home. The literature is absolutely u/s in this regard so the first stage is getting owners to measure the jet lengths, protrusion into the inlet tract,etc. Only then will we be able to work out what should be fitted.

My original query was thinking ahead, that at some time, the owners association may be faced with getting new jets made of the correct height to replace the (non-existent) current stocks. I had no idea how these could be bored to the correct orifice.

Chas

It has been said over the years, having bought an old bike get the carb and mag refurbished and you will get rid of most of the problems.

It is quite probable that jets were first drilled, then calibrated by flowing and finally stamped with a size. A flow test is very simple. Paraffin would probably have been used. All one has to do is to measure the flow rate (stop watch and measuring cylinder) for a given pressure drop (gravitational head). It would be interesting to know what the number on the jet actually meant.

It would be very easy to increase the flow by putting a chamfer on the jet entry. The result could be checked against the original by flow tests.

JA

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Interesting, and simple enough ... [for modern specifications]

MichaelG.

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Edited By Michael Gilligan on 17/01/2017 08:45:06

AMAL's note on Ethanol may be useful ... especially the comment at the end, about materials.

**LINK**

http://amalcarb.co.uk/ethanol-fuels

MichaelG.

Interesting stuff. Yes, who knows what 80+ years of previous owners have done to the carbs mixing and matching parts etc etc.

Charles,

Hopeflly it was self-evident from the AMAL quote that I posted, but [just in case]:

If, as stated, the current AMAL jets are individually calibrated; then they could be used as 'transfer standard' for your own calibration rig. ... You don't need to know the full details of their test; you simply need to work backwards from their answer.

Use whatever test fluid is convenient for you, and set the 'head' [pressure] to achieve the right result for your 'standard' ... then use that fluid, and that head, to test your own manufactured items.

MichaelG.

Agreed, lots of carburation problems are electrical. Whilst I restore the brass bodied carb on my 1929 bike (Bored the body and made a new slide) I am running it on an Amal monoblock. First kick starting comes by using electronic ignition.