Vince
New Member
Posts: 28
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Post by Vince on Oct 12, 2023 19:24:11 GMT
Why does my pre-monobloc Amal carb have two fuel inlets on the banjo?
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Post by buttybach1932 on Oct 17, 2023 21:36:39 GMT
Hi Vince
Is the twin inlet connection the fuel inlet to the float chamber or has the carburettor got a remote float chamber and the twin inlet is on the bottom of the carburettor.
A twin inlet to the float chamber would be used on motorcycles that have two fuel taps one on each side of the fuel tank.
A twin outlet from a remote float chamber would be used on parallel twins fitted with two carburettors and a central float chamber.
If it is a twin inlet on a carburettor with a remote float chamber, one connection would be for the float chamber and the other connection could be for a swill pot. These were used on sidecar outfits to keep the mixture stable when cornering. Also on a remote float chamber carburettor it could be a connection for a clear piece of pipe used to check the fuel level in the carburettor. On the Pre-Monobloc carburettors the fuel level should be 3/16" below the top of the needle jet. The connection is blanked off when not used.
There are several more possibilities. What model is the carburettor and what is it being used for.
Regards
Butty Bach
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Vince
New Member
Posts: 28
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Post by Vince on Oct 18, 2023 12:59:56 GMT
Hi Butty The carb is on a very rare James 1930 'utility' model. I say rare because it didn't feature in the catalogue for 1930 yet it's existence is verified by a road test in the June 1930 issue of The Motorcycle. It is a Villiers 2e engine and you might think it would have a Villiers carb but I'm told that Villiers did use Amal carbs on their engines. This was verified by Burlen the UK supplier of Amal carbs and parts, who dated it for me and identified the carb model. I have refurbished the carb and the engine starts and runs well. The throttle is of course controlled by a lever. I was just curious about the twin inlets. Funnily enough the tank has two outlets that are joined together, presumably to pass fuel from one side to the other and then there is a 3rd outlet which is the one that goes to the carb. Currently I have stuck a piece of plastic fuel pipe over the inlet I'm not using and heat sealed it. I love the expression 'swill pot'. Not heard that one before. I shall impress my friends with that bit of knowledge. See the attachments for pictures. Attachments:
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Post by buttybach1932 on Oct 18, 2023 20:09:02 GMT
Hi Vince Looking at the photograph of the bike, the engine appears to be a 196cc Villiers II E ( 2E ). The manufacturers code for the engine should be XZ. The II E engine was manufactured from 1930 to 1938. James first used the engine in their 1931 'model year' C12 Utility Model. Please note that the model year would nominally run from August 1930 to July 1931. The carburettor is not the correct one for the bike. It would originally have been fitted with a Villiers Middleweight carburettor. The carburettor fitted to the bike is a Post War Amal clip fitting type 275 or 276. The float chamber appears to be for a downdraught carburettor as it is slightly out of vertical. If you let me know the number on the carburettor, I can probably tell you what it was originally fitted to. If you want an original looking carburettor you may be able to find an old Villiers Middleweight or alternatively you may be able to find a Post War Villiers Type 4/5 which was fitted to the 197cc 6E engine. The Type 4/5 is basically an updated version of the Middleweight and both have a 15/16" bore. The advantage of the 4/5 is that it has a fuel filter on the carburettor banjo union and it is designed to fit an air filter. Both carburettors are two lever types so you have a throttle and a mixture lever. The mixture lever raises and lowers the throttle needle to richen and weaken the fuel mixture. The original fuel pipe on your James was probably ΒΌ" copper with a pig tail. The balance pipe that connects the two halves of the petrol tank would also be copper. My 1930 Rex Acme V10-A is fitted with a Middleweight carburettor and attached below are a couple of photographs. If you have not run an early two stroke before be very careful with the fuel / oil mixture. The engine has bronze main bearings that also act as the crankcase compression seals. The oil film in the bearing creates the seal. I would not recommend using modern self mixing two stoke oils in this type of engine. Villiers recommended using XL oil which is SAE 30 grade mixed at a ratio of 16 to 1. Also remember the II E engine has a cast iron piston and maximum engine revs are limited to around 4,500 rpm. If the engine still has its original piston it will probably be fitted with a Villiers 'Patented Inertia Ring'. This is the top ring on the piston. The ends of the ring should be touching when it is removed from the barrel. If you attempt to remove it it will be destroyed and you will either have to find a different piston or fit a ring peg and pegged piston ring to replace the 'Inertia Ring'. The idea of the Inertia Ring was that it stopped the top ring from becoming gummed up with carbon because it could rotate. It obviously did not work very well because new engines designed in the later 1930s did not use them. Regards Butty Bach    |
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Vince
New Member
Posts: 28
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Post by Vince on Oct 19, 2023 13:34:20 GMT
Dear Butty I'm not at all surprised that the carburettor may not be original but I'll think I'll leave it as I found it. When I first saw the bike (at Founders Day three years ago) it was originally spotted by David Wells whose a bit of an expert on these matters. I purchased it after he'd seen it and at the start of the restoration I had a number of conversations with him. He said, "There are no official James records. I have my personal records of over 500 pre war James'. This includes about 100 lightweights between 1928 and 1939. I cannot tell exactly the date of your frame but it will be late 1930 or early 1932. James only used Baker frames for 1931. Because of the engine type I said 1930 (assuming frame and engine were originally together). Going forward James used the Baker frame for this engine." And, "It cannot be later than 1930 as that was the last time James used that exact frame. They did use a version of it up to 1935 for the model 7 250cc side valve but the front loop was replaced by an engine cradle."As I mentioned before, the only provenance I have is the article in The Motorcycle. It's less than useful because it doesn't mention the model name or the engine used!! You do wonder what they found to write about. However it is dated June 1930 which is a big clue. In my original research I discounted the C12 as it had a tank mounted hand shift. The article in The Motorcycle clearly shows a gearbox mounted hand shift as on my machine. The balance pipe is still the copper original. I may well try to fashion a coiled copper pipe for the carburettor. I have been running a standard mineral 2T oil at 20:1 with Shell Super (5% ethanol). I haven't done many miles on it, the most in one hit was 10 miles out, a rest and then 10 miles back again! I do have some XL SAE 30 oil - would you recommend I go to the higher ratio?
Thank you for your information. I do find this element of classic / vintage ownership fascinating.
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Post by 1951superlux on Oct 19, 2023 13:35:29 GMT
If you want an original looking carburettor you may be able to find an old Villiers Middleweight or alternatively you may be able to find a Post War Villiers Type 4/5 which was fitted to the 197cc 6E engine. The Type 4/5 is basically an updated version of the Middleweight and both have a 15/16" bore. The advantage of the 4/5 is that it has a fuel filter on the carburettor banjo union and it is designed to fit an air filter. Both carburettors are two lever types so you have a throttle and a mixture lever. The mixture lever raises and lowers the throttle needle to richen and weaken the fuel mixture. I think that, were it mine, I would leave it as it is. You can restore a bike to the catalogue spec and then it tells you no more than you can find out by reading the catalogue. Bikes didn't generally go for long before their owners decided to change something and being non-standard does, in some ways, make it more typical of bikes that were in use. It's also interesting to speculate about why changes were made. A possible reason in this case lies in Butty Bach's info - maybe the owner didn't want to have two levers to worry about! Here for example, is the tank on my Vincent Firefly that a previous owner thought would be improved by having a reserve.  |
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Post by buttybach1932 on Oct 19, 2023 15:21:21 GMT
If you want an original looking carburettor you may be able to find an old Villiers Middleweight or alternatively you may be able to find a Post War Villiers Type 4/5 which was fitted to the 197cc 6E engine. The Type 4/5 is basically an updated version of the Middleweight and both have a 15/16" bore. The advantage of the 4/5 is that it has a fuel filter on the carburettor banjo union and it is designed to fit an air filter. Both carburettors are two lever types so you have a throttle and a mixture lever. The mixture lever raises and lowers the throttle needle to richen and weaken the fuel mixture. I think that, were it mine, I would leave it as it is. You can restore a bike to the catalogue spec and then it tells you no more than you can find out by reading the catalogue. Bikes didn't generally go for long before their owners decided to change something and being non-standard does, in some ways, make it more typical of bikes that were in use. It's also interesting to speculate about why changes were made. A possible reason in this case lies in Butty Bach's info - maybe the owner didn't want to have two levers to worry about! Here for example, is the tank on my Vincent Firefly that a previous owner thought would be improved by having a reserve. View Attachment |
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Post by buttybach1932 on Oct 19, 2023 15:42:31 GMT
Hi 1951superlux
I do not have any problem with non standard machines. None of my motorcycles are to factory specification for a number of different reasons. However I do like modifications to look reasonably period. One local chap who owns a Velocette has fitted modern upside down forks, a hydraulic disc brake and a modern LED headlight. The modifications may make the bike more useable but to me it just does not look right.
If the Amal carburettor on Vince's James works and he is happy with it fine. However setting up the carburation on an Amal that was manufactured for something else is probably more difficult than setting up a Villiers carburettor. With a two lever carburettor you can adjust the mixture as you ride along instead of having to dismantle the carburettor to make adjustments. The worst problem with the brass Villiers carburettors is trying to find parts that are not worn out.
I like the modification to the Vincent Firefly petrol tank, its tidy and functional. Looking at the photograph its not the only deviation from manufacturers specification.
Regards
Butty Bach
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Post by buttybach1932 on Oct 19, 2023 15:43:57 GMT
Dear Butty I'm not at all surprised that the carburettor may not be original but I'll think I'll leave it as I found it. When I first saw the bike (at Founders Day three years ago) it was originally spotted by David Wells whose a bit of an expert on these matters. I purchased it after he'd seen it and at the start of the restoration I had a number of conversations with him. He said, "There are no official James records. I have my personal records of over 500 pre war James'. This includes about 100 lightweights between 1928 and 1939. I cannot tell exactly the date of your frame but it will be late 1930 or early 1932. James only used Baker frames for 1931. Because of the engine type I said 1930 (assuming frame and engine were originally together). Going forward James used the Baker frame for this engine." And, "It cannot be later than 1930 as that was the last time James used that exact frame. They did use a version of it up to 1935 for the model 7 250cc side valve but the front loop was replaced by an engine cradle."As I mentioned before, the only provenance I have is the article in The Motorcycle. It's less than useful because it doesn't mention the model name or the engine used!! You do wonder what they found to write about. However it is dated June 1930 which is a big clue. In my original research I discounted the C12 as it had a tank mounted hand shift. The article in The Motorcycle clearly shows a gearbox mounted hand shift as on my machine. The balance pipe is still the copper original. I may well try to fashion a coiled copper pipe for the carburettor. I have been running a standard mineral 2T oil at 20:1 with Shell Super (5% ethanol). I haven't done many miles on it, the most in one hit was 10 miles out, a rest and then 10 miles back again! I do have some XL SAE 30 oil - would you recommend I go to the higher ratio?
Thank you for your information. I do find this element of classic / vintage ownership fascinating.
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Post by buttybach1932 on Oct 19, 2023 16:08:48 GMT
Hi Vince I should have looked at your photograph more carefully and noted that the frame on your bike is completely different to the C12 model. As you stated information on Pre-War James is very sketchy because they were bombed out in the war and most of their records were lost. I had a look at some 1930 model, catalogue photographs that I have and your bike is not shown. The 196cc models shown use either the 196cc Supersport or the twin port 1E engines, both have the Villiers Autolube system and the gearchange gate on the petrol tank. The 172cc B11 has the gearchange lever on the gearbox but has the twin port Autolube engine. Your bike appears to be the model with no name other than 'Utility'. Thanks for the copy of the 1930 article and the photograph of your bike. It looks nice and tidy. I would up the petrol oil ratio to 16 to 1. If you do not have your own machining facilities or a good mate that has, it can be an expensive job manufacturing and replacing worn out main bearing bushes. The petrol / oil engines are not quite so bad but the Autolube engines are a bit of a challenge because of the timed ports for the Autolube system. Attached is a sketch from Phil Irvine's 'Tuning for Speed' showing a carburettor swill pot. Some sidecar racers used a float chamber with no float and needle. Regards Butty Bach  |
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