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Hi folks, my patience has finally run out & I'm about to set my bloody bike on fire!

The reason for this is as follows:-

Ages ago, I replaced the fuel lines using something like 4mm dia tubing.... This was okay until the new MagDyno was fitted just before I took the bike to Normandy.

While in Normandy, the bike would start & run fine but after a short distance, she would cough, bang, splutter and stop, as if she had run out of petrol, BUT, on inspection there was plenty of fuel.... After a pause, she would start and run ok.

"Vac Lock" I hear you say... I checked the hole in the filler cap, there wasn't one, so I made one (nice and pretty it is too)... I thought this might cure the problem, but no... After the hole was made, I took her for a short run and covered about 1/4 mile when she did the same again.. cough, splutter and stop... I tickled the carb and nothing was coming out.

After what seemed to be an age, fuel seemed to get where it was needed and she started again & off I went.

Got home & had a thought... maybe the 4mm dia tube wasn't delivering enough fuel as was needed... So, I got hold of some 8mm dia tube & replaced the lines from both taps right down to the carb.

All looks really nice!

Now then, I decided while I was dealing with the fuel system that I would move the float bowl from its previous position "inside" to the more commonly accepted "outside" position.

Job done, switched on the fuel to check for leaks and VOILLA! None of the new stuff was leaking!!

HOWEVER (and this is where my patience has finally gone!) The bloody carb has decided to drip drip drip drip drip ad infinitum... I initially thought it was the two brass washers at the bottom of the carb where the float bowl rotates not seating correctly, so I cleaned them up & re fitted them... Switched on the fuel and drip drip drip drip....

I have sort of traced the leaking to the inside edge of the carb (Amal 276C1/B) where there is a shiny screw on ring thing, but that's it... I didn't touch that bit & now, I'm looking for the matches coz I'm sick of this monster! If it's not one thing going wrong, it's another, then something else, and then something else...

Anyone got any suggestions to make before I torch the little monster! Veteran or no veteran, she's getting it if a solution isnt forthcoming...


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Was it proper fuel line that you are using. as maybe it is collapsing internally. If you take off fuel line from carb does the fuel run out ok. take top off float bowl does it fill up. As you have fitted another mag- dynamo, what was wrong with the old one? Have you timed it on the right stroke. How good a spark have you. Take an old spark plug and open the gap to about 1/4" does the spark jump that when you kick the bike over, with a good mag it should. If spark is bad is it weak and yellow if so could be the condenser. A lot of so called fuel problems often turn out to be ignition.


The correct fuel line is 1/4"! Your leak drip drip is probably nothing to do with gaskets but more likely the wrong float level or the needle valve not seating properly.

I would go back to basics. Drain the tank and remove the taps. Check for crud build up at the filters and blow the taps through. Next remove the float bowl, strip and clean it out. With the float bowl assembled and upside down, you should NOT be able to blow through the banjo fitting without operating the tickler. Take this opportunity to also remove and blow through the main jet and needle jet.

Usually if the float level is high and a drip occurs it will usually not be much of a problem once the engine is running. Ron

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The float needle should have only one groove and the float height isn't adjustable...

To my knowledge the only way to alter that in relation to the carb is to change the mixing chamber lower fitting...

The M20 should have the short fitting where the hexagon used to tighten it is directly below the threaded part with no real 'neck' between them...

Make sure the washer inside the mixing chamber lower fitting is good and that you have tightened the fitting sufficiently...They have to be tightened till they squeak for mercy...Ian

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I have seen at least one float needle that has more than one groove. This is in the carby that I've just disassembled from my M21 project bike which has the Allparts brass carb body, so I don't know if this is also non-standard.

John Parker would be the guy to answer this I suspect.

Generally I'm with Ron on starting at the top with the problem and running through again. My 276 on by M20 tends to wear a little when standing, but as it's not enough to call a leak and doesn't cause her to flood at starting or running I leave her like that - especially as I've not yet been successful in removing the float bowl top from that carby.

I've had trouble with my M20 not running at full throttle, spitting back, etc. which in the end I think is fuel starvation due to crud in the feed from the float bowl. That last time this happened I deliberately left the fuel check till last to confirm this was the cause, which it seemed to be. So it's possible your problem is related? Some 4mm metric copper pipe (Google tells me) is 0.45mm wall thickness, so that the ID of 4mm is a fit over a 3mm pipe, but there are lots of variations on wall thickness. 1/4" tube according to this site has an ID of around 0.19" so 4.8mm. So that might not be helping?

Hope you don't resort to torching the bike....



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As usual Ron and Ian are spot on with their advice. Amal float needles used to have only one groove but these days they supply it with two grooves about 1/4 inch apart to facilitate the plastic float which does not have the bow clip on top and uses a throttle needle clip to hold the float in place. So bottom groove for the new white plastic float and top groove for the old style copper or brass float. I have seen numerous float needles over the years with up to five grooves hacksawed in to them. Ian is correct that if the big washer inside the bottom nut that seals against the bottom of the jetblock is not done up tight or is of a non compressable fibre material you will get leaks. The Amal supplied gasket is compressable.

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