Norton spray tube - will it weaken or enrich fuel mix ?/changing spraytube

[hoogerbooger]

I have a Concentric Mk1 on my B40 that has the Norton spray tube, with square cut out facing engine.

What should the effect of the cut-out be on the fuel mix? weaken or enrich ?

Also  I see elsewhere that the spray tube can be tapped out...so I could potentially put a 4 stroke spray tube in. If anyone has changed spray tubes and has an idea how best to do this with the Norton shaped tube, let me know. last think I wan't to do is have a go, fail and end up with a mashed one stuck in.

(need to be a member to post on the Norton Owners Club forum..otherwise I'd ask there)

[Richard Mills]

I remember tapping out the spray tubes on my Commando carbs. many years ago. Can't remember why I did it, but don't remember any difficulty doing so.
Richard

[hoogerbooger]

Hi Richard

can you remember more about how you did it ?

Do I just need to find a good solid flat ended object as a driver that will contact all of the  top semi-circle of spray tube  ?

my worry was that with only a semi circle of brass it may distort before it budges free

[Richard Mills]

Sorry it was a long time ago and, probably because I didn't have any problem, I can't remember. Were I to do it again I would choose a soft metal drift if available; limited choice so it would probably be aluminium.
I would suggest that you first try a sharp tap using a light hammer. If this doesn't budge it then let me know and I will have a go on an old one and report back!
Richard

[Richard Mills]

...........or a piece of wood.

[hoogerbooger]

Scary !

Drilled holes in a flat wooden block to sit the carb top flush on. Used a wooden dowel as a driver to get initial spray tube movement, then used a pencil as a driver that was fractionally narrower than the carb body hole, but which wide enough to jam in the spray tube .

The replacement 4 stroke spray tube proved fractionally wider than the one I took out. Nearly went pear shaped as snagged on last part of thread went a little off square and  knurled edges started digging in on one side. Managed to get it out, sand down the snagged bit . Sanded down the knurls so not quite as wide. went in easier then. tapped in with blunt end of a drill bit as the driver. 

all good fun !