'99 RMK Fuel Vent leaking

The vent line often dribbles fuel out, both when riding and when stopped. It is intermittent, but often enough to be very annoying and dangerous as well. Also enough to affect mileage. It seems there is pressure going back up the fuel line somehow. I've loosened the fuel cap when it happens, and it stops, but only until the cap is tightened again.

This is the sled with the factory primer installed, and I see some thread references to this being a possible culprit, but primer is between the pressure side of the fuel pump and the carbs, I cant see how that could allow any pressure back into the tank. I've pulled it and it seems to work and the valve is tight so appears to be good anyway. I put a clamp on the lines to it and the problem persists.

Sled only has 3000, 2500 by me.

Could it be blowback somehow from the fuel pump? Is there a backflow valve in the fuel line or pump which is supposed to prevent this? I don't see anything unless in the pump of fuel shutoff valve.

Thanks everyone

Thanks

The line routing is OK, that isn't the problem, but good thought. If the line were larger diameter it could let the air by and not take any gas with it like the short ones on top of dirt bike tanks.
The primer inlet being moved back to the inlet side of the pump could be done, but I think it would then be possible (but not likely) for any pressure leak back through the primer to get to the tank, which it can't now. THanks for that hint though, I will be sure to reroute it once I find the culprit.
I'm going to pull the pump off and disassemble it to see if there may be a leaky inlet valve which could possible let a bit of pressure back upstream to the tank. There is just no other possible source for pressure to the tank that I can imagine.

Ill post here the solution if I can find one!

Thanks guys!