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1949 Amal carb - runs ok only when I cover it

Submitted by paul_greene on Wed, 12/08/2015
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Hello,

Here I am finishing up a normal service to this nice 1949 ES2 and although it starts right up, it will only remain running if I cover up with my had the carb trumpet.

Tried alterning all external screws adjunting the air needle but no luck.

Spark plugs in on the dark side.

Any clues?

Cheers,

Paul.

Submitted by david_cooper on Wed, 12/08/2015

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Remove the jet block and clean the pilot galleries. That's how mine behaved and was completely cured.Getting the block out needs a mixture of care and brute force. I think there was some post about doing it without damaging anything a few months ago.

Submitted by paul_greene on Wed, 12/08/2015

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Previously David Cooper wrote:

Remove the jet block and clean the pilot galleries. That's how mine behaved and was completely cured. Getting the block out needs a mixture of care and brute force. I think there was some post about doing it without damaging anything a few months ago.

Thanks David. I thought I had cleaned up everything but looking at my photos, looks like the one thing I did not remove was the air adjuster.... will search for the post you mention.

Cheers,

Submitted by david_cooper on Wed, 12/08/2015

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Paul-have a look at the Amal site with exploded views. The bottom has to come off (unscrew) and the internal block entirely removed downwards out from underneath. I did it by using a round snug fitting wooden dowel in from the top, and gently tap it upside down on the bench to drive the block out because it was gummed up. I think hot water should have been used to lessen the force or it's easy to bend the jet block. It has a rather fragile narrow waste.Good luck ad take careDavid

Submitted by richard_payne on Wed, 12/08/2015

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I'm sure that David is correct in his assessment of cause and cure. I always place my bodies in a small bowl and pour a kettle of boiling water over them. The jet block can then be removed by tapping on an upside down hammer handle or similar.

It shouldn't need too much force and as David indicates, the block is quite vulnerable (it's actually a three-piece soldered brass construction).

The alternative is to ride in an ex-army greatcoat. They spend most of the time being sucked into the inlet !

Submitted by paul_greene on Thu, 13/08/2015

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Thanks David/Richard. Yes, I dismantled the carb although I did not go all the way since it seems pretty stuck.

Check out the jet's! incredible. Amazing it even started.

Although it starts right up and it idles.. I am getting serious backfires coming out of the carb!.... small flames!

after a good clean........

Submitted by jim_royce on Thu, 13/08/2015

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Hi Paul,

Next task check the valve clearances. If the inlet is being held slightly open when it fires it will do what you describe as well as spitting back.

If these are fine check the timing but if this is right a compression test might be in order.

Jim

Submitted by paul_greene on Thu, 13/08/2015

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Previously jim_royce wrote:

Hi Paul,

Next task check the valve clearances. If the inlet is being held slightly open when it fires it will do what you describe as well as spitting back.

If these are fine check the timing but if this is right a compression test might be in order.

Jim

Hello Jim, I had done all the homework before, timming, valve clearances, point gap, spark plug...

This bike had a rebuild engine a couple of years ago with almost no use, but here the fuel is very poor and when left standing, it becomes a very thick glue! blocking pretty much everything.

Will give it a compresion test to see what comes up.

Thanks.

Submitted by paul_greene on Thu, 13/08/2015

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Thanks David/Richard, looks like the internal block from the AMAL was also pretty blocked. It was difficult since I was worried to break or bend the bronze part, but boiling it in very hot water did the trick.

After polishing it, it was a lot easier to place back on to the aluminun carburator.

Started her up and she idles beautifuly. Gather all my other Amal carburators will be needing this service too!

Submitted by dave_graham1 on Fri, 14/08/2015

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It would be a good idea to get a gauze flame trap on your carb in case it spits back when starting. My WD16H had just a bell mouth, but after it caught fire twice when starting I fitted one the same as my ES2.

Attachments DSCF0044%20crop.jpg

Submitted by richard_payne on Fri, 14/08/2015

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That carb really was very very bad. Was the mouse still nesting in there ?

There is quite a lot of wear to the slide guide on the jet block. It might not be a bad idea to include a new one the next time that you're ordering spares. To be honest, I think that I'd be looking for a decent spare carb.

 


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