Re: Re[4]: Cold Starting (or not starting)

Posted by Arthur Farrow on Jun 21, 2020; 2:24pm
URL: http://silk-motorcycles.221.s1.nabble.com/Cold-Starting-or-not-starting-tp5001798p5001959.html

This is all very odd.

My bike has a Mk 2 Concentric ( Made in Spain) L2932 which measures up as about 33.5mm bore (then a rough 2 stamped below number ) so being a early one the smallest of the carbs fitted

My float needle looks to be same as Concentric Mk1 i.e. 622/068 in Brass. Quite small and way smaller than the large Alloy one listed for the Mk2 622/149.

My son Thomas has Mk2's fitted to his Vincent Rapide and has never had a flooding problem but the machine does not have the angle of a Silk carb. He is a Chartered Engineer working/developing  8-12 cylinder high power engines for original major manufacturers. He reckons to have read somewhere that the slot inside the float chamber was added during production to make fuel flow freer and we both recollect something about needles being changed to Alloy to stop sticking  . I guess they must have changed the dimension of the needle too and of course its seating cast into the float bowl.

I know Mk 1 Concentrics had different bowls for alcohol using needle 622/149

The Burlen issued 2019 11th Edition Amal book list 5 different float bowl using seats of 2.5mm,1.6mm (pump feed seating) 3.2 mm (standard seat) 4.0mm (alcohol) and 1.25mm but does not refer to what these "seats" are other than the notes in ( ). Burlen list 4 of these float chambers now.

In another world I would call Burlen and ask advice but I have never found them at all helpful

In the meantime I found RGM Norton sell new Float chambers 2622/057S for a lot less than Burlen so I've ordered one. This has a 3.2mm seat and I'm hoping my new big float needle will work nicely with that but I'm  really wandering in the dark.

Am I the only Silk owner whose carb has the small brass float needle???