WD/CO Running Rick or Weak?

[gary0003]

My R/Enfield 1944 needs the choke about half closed - does this suggest the mixture is too weak or too rich please?

All jets etc are correct but everything is probably a bit worn!

[79x100]

The choke richens the mixture by blocking the air supply so it must be lean at the moment, but as it lowers from above, 'half choke' will only have an effect above half throttle. They're mostly used either 'on' or 'off'

 

My first step, assuming there are no obvious air leaks would be to check fuel level (you can run it with the cover off) and then to carefully remove the jet block and make sure it is all clear. This is quite a common problem and it can't be cured without fully dismantling.

[Johnny]

Is the petrol fresh?

I've heard of (and experienced) lots of odd running issues recently due to stale fuel.

Modern fuel only seems to have a life of a couple of months before it goes off.

The bike might still start but won't run properly - often with issues like the one you've described - and it's easy to get drawn into thinking there is another issue!

If it was running properly before, and especially if it hasn't been used for a while, try putting some fresh juice in before getting your hands too dirty!

[Sean N]

Needing choke and / or revs to run may also indicate air leaks somewhere.

[Richard Farrant]

Needing choke and / or revs to run may also indicate air leaks somewhere.

 

....... and with a motorcycle carb the first place I would look at is the flange face where it bolts to the head, these are often overtightened and distorted. Take carb off and put a straight edge across flange bolt holes. Common source of air leak or weak running.