Yes I understand for the effect of the castor oil like a little piston ring. Thank you!

The seal on the solenoid, it's aim to separate the inlet from the outlet of the valve, or just avoid leaking from the top of the valve?

I try a lot of things this morning, change again hose, change tank location, change position of the valve (outlet up, outlet down,...), test all the fuel line to search any leak, but nothing form me solve the bubbles problem.
I noticed when the outlet of the housing of the valve is down (toward the ground) and hose came up to the carb, I have no more micro bubbles, but every ~10s a big bubbles, like if micro bubbles agglomerate in one big bubbles.
And always no bubbles from the hose between the tank and the valve.
I'm thinking there is a micro leak but where? May be if I worn the seal during the assembly of the valve with the housing?
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