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

email (option): ronpier@talk21.com

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

email (option): ian@wright52.plus.com

Hi

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 https://www.plumbingsupply.com/coppertubing.html 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....

Cheers

Richard

email (option): dickie.bobbie@hotmail.co.uk

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.