I have noticed that the Commando has a cut out in the carburettor spray tube that faces inwards towards the inlet manifold which differs from the 'normal' tube which is the same height all around. This is obviously done for a reasonbut does any one know why and what effect it has?
The reason I ask is that I have purchased replacement bodies for my carbs and they have a different spray tube; it is not difficult to change it, but what effect would not doing so have?
Thanks,
Keith
The full hight spray tube…
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These are the different sp…
These are the different spray tubes from the amal website in the attached pic, the full height is for 4 strokes, slanted for 2 strokes , stepped for Norton 850's and the final one for Triumph Triples. The Norton one came about from a noise test which required the bike to be able to accelerate from low revs with the throttle snapped wide open, the 850 would not accelerate with the normal 4 stroke spray tube and would have failed the test. Amal came up with the stepped spray tube which kept a small residue of rich mixture so when the throttle was snapped open the bike would accelerate. So unless you snap open your throttle at low revs you will not notice but the jetting may be affected but with today's petrol the factory settings are only a starting point anyway.
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The crucial thing with the…
The crucial thing with the cutaway spray tubes is that they were introduced with their own special needle. They'll work fine with the correct needle, as will the standard type but don't mix and match them.
From memory, the cutaway needles have a longer thinner taper and are marked with a lightly ground identification ring
I run an 850 with non-balance exhausts, a 750 air box and non-cutaway spray tubes. I'm happy that this gives the best results for me. Changing any of these could give different results.
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The full hight spray tube is for 2 strokes. It will make a Commando run badly.