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How to start a Superior 25HP ?

Hi, my friend acquired a Superior 25HP engine, and while these are not common in the Netherlands, he has no idea how to start.

There is a big pot, (see picture)where the gas go in with a valve, what is the function of this valve ?

Please can someone explain how to start this engine?

Anton van der Cruijsen


Bob Willman

Last Subscription Date
It looks like the pot in your photo is the fuel valve that is controlled by the governor. My guess is that the natural gas or propane enters the bowl from the bottom center and a plate controlled by the governor raises and lowers to determine how much gas enters the engine. I must admit that I am not familiar with this type of fuel control.


Bill Hazzard

Last Subscription Date
Anton, the poppet valve in the center just closes of the fuel when the engine is not on the intake stroke. The air comes in through the bottom and the gas in the side. The governor linkage should connect to the throttle valve below the governor. If the valve was not there the gas would flow all the time. There is a compression release cam which will allow the engine to be turned for starting. You also need to retard the timing for starting.


looks like your valve is missing the rubber disk that closes off the air input. It should fit the outer step in the pot. (My valve was missing so I made one out of a light aluminum disk with a piece of tire tube glued to it to quiet the closing noise) The air draw on the intake stroke is what actually pulls the valve open , thus allowing the gas port to open as well. I also have a very light spring on mine to hold the valve closed.

Are you planning on using propane or gasoline on this engine? I'm running propane on mine, and usually prime it by pulling up on the top of the rod several times and letting some gas into the intake chamber prior to starting.

It looks like you are missing the throttle rod between the governor lever and intake butterfly.

BTW, I use air to start mine, it is a whole lot easier to start that cranking on the flywheel. Also very easy to plumb.
Thanks guys for helping with advice, my friend is indeed missing the air valve so next week we will make one. we also use propane but the engine will not start, maybe the gas/air mixture is not all right hope to have more succes when we have a proper air valve

Again many thanks!



It took me a while to get the settings correct. shut the air (choke) way off and bring up the gas from off very slowly. When I first started mine (new rings) I actually jacked up my cub lowboy rear tire against the flywheel and just let the engine spin. Eventually, I found the right combination. It was a lot less air and fuel than I expected. I now have my settings marked on the valves. I now set the choke about 3/4 closed, Set the gas to my start mark, pull the air valve open a couple of times to charge the intake, then give it a blast of air to start. It usually starts on first revolution. I let it warm up a bit then advance the timing a bit, close the choke slowly to 90% while I lean out the gas to slow it way down.

BTW hopefully you have the compression reducer peg. It will be a lot more difficult starting with full compression.