Hitchcocks Forum

Evening all,

If I could pick your brains , I notice that on some enfields and other older British bikes that the pipe colouring out the top of the engine can tend to either be blue or a yellowish colour , I believe that this is a sign of either too rich or too lean , however what is the correctcolour that a well used bike exhaust pipe should be ?

On another note Had another lovely ride today bumped into a guy with a 1928 ariel with fishtail exhaust gorgeous machine.sounded delightful.

Thanks Reds

It can also be an indication of someone who rides it like they stole it.

I think the thickness (gauge) of the pipe also makes a difference. I found that after swapping the original pipe on my Sixty5 (which weighed a ton!) to a pipe of lighter gauge, the chrome discoloured much more.

You'll probably not stop a big single getting at least a "straw" coloured pipe but if it's very blue it's an indication of incorrect mixture or ignition timing. The colour is a thin oxidation layer which changes colour with temperature (tempering colour) It will come off with a chrome polish and elbow grease. Those finned collars clamped round the pipe help to dissipate the heat and so help to prevent the colour forming.

Chrome heated by a correctly fuelled engine should be light straw colour. The reason Jap bikes don't discolour is that the pipes are double walled.

Well, some of them are Nigel.