2013 Twin Cam Softail 103. Done 60,000 Ks. 

Hey Rat, from memory I think there is a minimal pressure, thinking was 15 psi or similar, so not a huge issue. 

Had mine jump out when I started it once, slightly over full oil tank and I think the o ring had hardened with heat.Replaced the ring with one I happened to have that was a bit thicker and a little tighter fit and remover a small amount of oil, hasn't done it again.

Make sure oil level not too high. 

Isn’t there a story about that. Bloke yells out  “ hey, look at the 2 dipsticks on that Harley”. Rb spends 10 minutes looking for the second. 

steelo, its Sat night .. most of us , arrrr now i get it.

If you have even slightly more oil than it likes then this will happen. Very frustrating until you find the happy medium.Oil level on full line no good About halfway between low and full when hot.I topped mine up recently as I thought it was a bit low and hello leaking again.Good luck

Thanks guys, it’s a used bike I’m thinking of buying off a mate so I’ll run through the suggested checks.

It's a Harley thing. My dipstick pops out about 15 minutes into every ride. Just gotta keep it zipped up. ;-)

Check operation of the head breathers, and perform a leak down test if your worried. The oil tank should have a breather balance tube. Check if it's not blocked.