Lister D carburettor

Hi All,
I’ve been given a Lister D carburettor, in poor state, but was missing the main jet.
I’ve now a replacement jet ready to screw in, but was wondering if there should be a fibre washer added, as it seems the jet once screwed in the locking screw doesn’t line up, only if tightened another flat or so, which seems very tight! A fibre washer would allow me to reduce by one turn with a good seal from washer.
I’ve just noticed my up n running Lister seems not to have a washer! Is this correct
Your replies much appreciated
Mark

No washer
It is indeed tight to line up

Thanks Andy
Cheers
Mark

It’s occurred to me that the jets may have been fitted individually to  each carb body and drilled in place for the securing screw.
If you can’t get it to line up you may be best doing this.
Unless every machine tap was presented exactly the same to each hole then the thread may start at a different point on the clock face as it were. As I say mine was tight but at least my jet was not from another carb body

Good point Andy, that could explain why it’s not lining up, I shall look into this further
Cheers