22-02-2019, 01:57 PM
Thanks for all that and this morning I've made a couple changes.
If my math(s) is right, pressurizing the tank to 1 psi effectively increases the head by about 26 inches which I'm sure is plenty. Incidentally while trying it out yesterday, with the petrol tap open I pressurized the tank up to 5 psi which confirmed the filler cap was sealing but the carb needle valve had still not cracked open which was one reason for thinking about a relief valve.
Anyway I've now incorporated an adjustable relief on the tank connection which I'll set at about 1.5 psi and included a bleed screw on the cap so that I can release the pressure at the same time as turning the petrol tap off.
If my math(s) is right, pressurizing the tank to 1 psi effectively increases the head by about 26 inches which I'm sure is plenty. Incidentally while trying it out yesterday, with the petrol tap open I pressurized the tank up to 5 psi which confirmed the filler cap was sealing but the carb needle valve had still not cracked open which was one reason for thinking about a relief valve.
Anyway I've now incorporated an adjustable relief on the tank connection which I'll set at about 1.5 psi and included a bleed screw on the cap so that I can release the pressure at the same time as turning the petrol tap off.