When you say needle and tip - are you referring to the entire head assembly or just the tip?
If you mean the entire head assembly, it may be one fo several things.
1. There may be a hair line split in your paint tip.
2. Is your spray regulator completely snugged into place?
3. It may be the internal teflon needle bearing (not likely if the other size needle and nozzle work properly)
4. as indicated already it may be the teflon head seal has some disconfiguration, but that should not be the case on a new head asembly.
If you mean only the tip and not the whole head assembly you may have the fine tip and needle set up with the medium spray regulator. If this si the case you will need to also change the spray regulator to the fine variation.
Additionally, I would recommend staying at leat at about 18psi., if at all possible.
If none of this solves your concern, please email me direct at kenbadger@aol.com for further direction.
take air,
ken
www.myspace.com/kenbadger
www.myspace.com/badgerairbrush
www.badgerairbrush.com