Main jet - which way up?

[oldchuffer]

Putting new jets in my carbs and i notice the ends are slightly different, one end seems to have a deeper drilling than the other, does it matter which way round they go?  Which end should go in the carb first? [ Guests cannot view attachments ] [ Guests cannot view attachments ]

Pic a shows the deeper end, Pic b not so deep.

[McCabe-Thiele (Ted)]

Can you not check them against the old ones?

There might be markings where the O ring was.

[Johnny4428]

Couldn’t tell you the correct way up but with the needle tapered it will make a difference which way up. IMO

[McCabe-Thiele (Ted)]

I've just checked my part dismantled spare set of 400 carbs.

The drilling on the top end is shallower than on the bottom.

The shallower side is the upper part next to the "O" ring from what I can see.

It looks to me that as the needle does not go down that far that its just the hole diameter metering the fuel flow. I am thinking the mixture is controlled by the emulsion tube & the needle.

Your second photo shows the top of the item.

[Bryanj]

Look at the originals, numbers and emblems are visible when fitted.
Better cleaning the original than fitting pattern, goes for all the brass

[oldchuffer]

Well i would have looked at the originals but the carbs didnt have any, hence my question. Yes i know they say "never buy a bike in boxes" but after restoring around 12 bikes i was ready for a dfferent challenge and i'm determined this one will run one day.

[oldchuffer]

Thanks for the info Ted.

[LetsRide]

This has just answered a question I came on to the forum to check out. So thanks for asking the question OldChuffer and thanks for answering it Ted. Time for me to get off the computer and head out to the workshop again.