Check valve in fuel line

[Brian Rupnow]

Today I seen something I had never seen before. I have had others tell me about the necessity for a check valve in the fuel line of a hit and miss engine. I didn't disbelieve them---I just filed the information away in the back of my head with 67 years worth of other "things worth knowing". This afternoon while attempting to run my sawmill with the Odds and Ends hit and miss engine I just finished, I actually got to see this happen. I have a transparent fuel line leading from the bottom of my fuel tank up to the carburetor. I would crank the engine with my electric drill, and choke it a bit with my finger over the carb untill it fired and ran. When the engine was "hitting", the fuel line would stay full. As soon as the engine went into "miss" mode, the fuel would all run back down the line into the tank. Then when the engine slowed and the governor weights allowed the exhaust valve to close, there would be a definite pause while the fuel rushed back up the line to the carb and the engine would fire again. This was a really great thing to observe, first hand. This week I will build a check valve and put it in the fuel line.

 

[Brian Rupnow]

I got up early this morning before hoards of egg hunting grandchildren descend on my house, and did a quick design of a check valve. This should do the trick.

 

[Brian Rupnow]

Got all finished up just as the gang rolled in. Weston---You're right, I read the same, so I placed the bearing in the brass seat and gave it a good whack with a 1/8" punch. That seemed to make a difference in the old "put it in your mouth and blow as hard as you can" test. The ball seemed to seat more completely after a good whack with a hammer. Will Loctite after everybody leaves this afternoon. I didn't put a spring in because these small bore engines don't create enough venturi effect to lift the ball off its seat against spring pressure.

 

[Brian Rupnow]

The check valve works good. I don't see any "run back" of the fuel in the line now. Of course, no good deed goes unpunished. Somehow, in all my screwing about with the carb, I have mucked up the gasket which seals the carb to the cylinder and the engine now doesn't want to run except in short bursts. By using the old liquid dishsoap trick, I see it blowing bubbles around the connection between the carb and the cylinder. Tomorrows job will be to replace my cereal box cardboard gaskets with some better gasket material.

 

[terrywerm]

Tomorrows job will be to replace my cereal box cardboard gaskets with some better gasket material.

Now I don't feel so bad because I now know that I am not the only one to use cereal box cardboard to make gaskets. It actually works quite well in most cases.

Anyway, thanks for the post about the check valve, I never would have known.

 

[mcostello]

Be careful using gasket material from high fibre cereal as it might tend to "leak" more.