Originally Posted by
mikes68charger
Sorry 160, I got it from my boy, it was in a Aviation Design Super Scorpion, We used just regular Green Colman Propane outside the jet. But I was thinking If the propane was onboard it would be like having kero start.
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You can't use on-board propane. Propane has too high a vapor pressure (150 psi at 90 degrees F) and it will blow the hoses off all of your fittings. If you use propane to start, you need to use an off-board gas container with a pressure regulator - like this one:
Dreamworks Model Products LLC
For "gas start" engines (love mine too - no hot starts!), most guys use a 70% 30% Propane-butane mix. That has a lower vapor pressure which is easier on the tubing and fittings. I have, however, converted all of my gas start jets to off-board gas (i.e., no onboard gas tank) its safer, and actually easier - just connect the off board gas tank, turn it on, start the engine, turn off the gas, and disconnect the tank.
I use the same gas Rav does, from REI as well. Unfortunately, the BVM valves are no longer available. I got one from Altecare RC that has a screw valve which works great on those tanks. Unfortunately, they don't sell it anymore. However, I think you could get this one:
http://www.altecare.com/airpropanetankvalve.JPG
And mate it with a 4mm festo valve to do the same thing...