Author Topic: Amal 274  (Read 3597 times)

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Offline Evanc

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Amal 274
« on: 12 Aug 2014 at 12:26 »
Hi fellow Douglas owners, I am having some problems with my Mk V and I feel I have a carby problem which seems to be the jet block is slightly smaller than it should be. I am hoping someone out there may have some parts or a 2nd hand carby I can purchase. I have contacted Burlen and they feel I am on the right track but cannot supply parts. any clues would be appreciated as I believe I have all my other problems sorted now,
thanks, Evan

Offline eddie

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Re: Amal 274
« Reply #1 on: 12 Aug 2014 at 14:46 »
Evan,
         The correct choke block for the 274's on a Mark should be stamped '21' on the top - this denotes the bore of the choke block. Also, the choke blocks are handed, but it is possible to fit the wrong handed block into the carb body. It seems that all choke blocks are made as right hand fitting with regard to the locating pin in the side, but the drillings for the slow running mixture are handed - as is the slot to clear the throttle stop screw. Maybe you have the wrong hand fitted - in which case there will be no control of the slow running mixture.

  Regards,
               Eddie.

Offline Evanc

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Re: Amal 274
« Reply #2 on: 13 Aug 2014 at 10:08 »
Thanks for the info Eddie, I'm sure it is the right side but it is too small and is sloppy inside the carburettor. This carby is running very rich and to get it to idle I have the mixture screw out about 4 turns. the other side seems to be a little lean and the mixture screw is out about 3/4 of a turn. Any Ideas where I might find a 2nd hand carby?
thanks, Evan

Offline eddie

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Re: Amal 274
« Reply #3 on: 13 Aug 2014 at 11:18 »
Evan,
         At the moment we don't know whether it is the choke block or carb body that is at fault. I have checked some damaged choke blocks that I have and they all measure .998" dia where they fit the bore of the carb - and the bore of the carb should be 1.000". Also, is it the RH or LH carb that is giving the problem? Once we have established what is at fault, I may be able to help out with some bits.
   With regard to the other carb running weak - that sounds like a partially blocked jet. When set up correctly, the engine should tick over smoothly with the slow running screws wound out approximately 2 turns. The choke blocks have a 1/4" drilling for the primary air - opposite that, there is a shallow drilling  with a very small hole (.018") in the bottom of it, another drilling (.036") at the top, and a third drilling (.048") to the side. Make sure all these are clear. Also, the very small drilling meets up with a vertical drilling from the base of the choke block - make sure that drilling is also clear.

  Regards,
               Eddie.

Offline Evanc

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Re: Amal 274
« Reply #4 on: 18 Aug 2014 at 12:18 »
Hi Eddie,
I have just stripped down and checked out the carbs again and this is what I have found.
The right carby, the one I feel was running lean, had a totally blocked passage in the carb body for the mixture. It had been blocked with corrosion type crud. I have cleared it but have not run it yet as the weather here is atrocious. I would think this should cure my mixture problem on this side. by the way I'm sure the jet blocks are in the correct side for both carbs, all passages line up and are clear.
Stripped down the left carby and found very little. All passages are clear, the jet block is stamped twenty one though it was very hard to identify as it has been bashed quite a lot over its life. This is the jet block that seems too small. It has appears to be plated but it has worn off on two quarters of it.I am not sure if they had two types but the right one seems to be solid brass and the left one appears to brass that has been plated.
I am interested to see how it runs with the right side hopefully working properly now.
I may have sourced some parts locally so I will keep you posted if I require any, thanks so much for all your advice to date, as I mentioned I have nearly got all my little problems sorted and apart from the poor idle I think it is almost perfect.