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Questions About Propane Conversion

JB Tommy

A few questions before i try my hand at converting my JB from gasoline to propane. 7.5JB-FL with gas/gaseous carb - i have all the propane equipment and am ready to convert. can i start the engine and let it run out of gas with the fuel line shut off or do i still need to drain the bowl and fuel pump? will i hurt the (mechanical)fuel pump if i leave it connected with no fuel supply or do i need to remove and plate it over? i know i need to block off the fuel line at the carb after i connect the propane supply line. what about the choke? i have an electric choke with a heating element and i've read that i need to wire it open some how. is the choke totally moot after conversion to propane and what do i need to do with it? the parts diagram shows some kind of wire that is used for holding the choke vaccum diaphram open. what about ignition timing and spark plug gap or points gap? the operator's guide does not spec a different setting for gaseous fuels.

i'm swapping a nice 12 gal maring fuel cell for the propane set-up so i hope this is worth it. it has 2 full 40# bottles and the soleniod/filter/regulator/tubing ready to go. i read here that propane and nat gas make these units happy for a long time!

thanks in advance for the replies! :) :)

Andrew Mackey

Last Subscription Date
Here's a personal preferance - utilise both! Propane can be a bear to get lit off, especially if it is below 40 F. T have a fuel valve shutoff before the carb, it won't hurt the pump. The colder it is out, the worse the problem. Most commercial conversions utilize both. When starting cold, start on gas, and after a few minutes, when the engine is warm, shut off gas. When the engine begins to stall, open propane, and the engine will continue to run. When hot starting, just start on the propane.


I have converted the cck, bfa,and bge models. Once you go with propane you will never switch back. All my conversions were done with an engineered kit for my particular application. I have found no cold weather starting problems. These units now start cold or hot like a fuel injected car motor. No choke problems or surging. Bank they fire right up and get a little oiling and up to governor speed. To date the coldest i have started at is -15 degrees.
You will need to make the choke stay open. Some chokes you can just unhook the power wire and loosen the adjustment screws and set the coil as far lean as possible. You dont want the choke on at all. I just shut the gas off and run the carb dry. I unhook the gas supply and cap the lines before the pump. I to have wondered about the mechanical pumps diaphrams. However you could take it off and let it dry out on the shelf. Either way i think there is good and bad. Electric fuel pumps are nicer because i just unhook them and wire the propane lock off solinoid into the same leads. Timing has stayed the same. Plug gap i close to .018 to.020. Hope this helps you some. The one thing i was told is cold weather starting is unique to each and every combination. So far all i have done has put a smile on everyones face and they all say why did i not do this years ago. With propane it can cause the oil to milk if you just run it a few minutes and shut it down constantly. Mine have always had to run for hours so milking was not an issue. Consumption is about the same as gasoline however at todays prices propane is about 50 to 75 cents a gallon cheaper. Hope this helps you out...

Gary V

Re: Onan BGE Propane Conversion

I have an Onan 4.0BGE-1R/26100C that I would like to convert to operate off of propane. Is there a kit that I can purchase to do this modification, and where would I get it?


here in texas, ive started up with natual gas and propane as cold as 20, no problems what so ever, motors love propane and nat gas, as long as you have good compresson, and or high compresson heads.