1964 Johnson 40 HP RDSL-26 Fuel Problem

[johnlazelle]

Hi Everyone,

I have been working on my 1964 Johnson 40 HP RDSL-26R and out on the water it runs at low speeds ok, but won't run at high speed. When you give it gas, it dies out. I have tried different gas and gas tank, checked filter (it's new), checked float and needle valve (both new) and the carb has been rebuilt. I had to replace the fuel pump and the part number the part number that was sold to me was 391667. I notice that the fuel filter bowl does not stay full. I am wondering if i either have a bad or wrong fuel pump, any suggestions?

Thanks,
John

 

[hardwater fisherman]

make sure you have spark on both cylinders. my 1976 40hp will start and run at low speed on one cylinder. start it and pull off one plug wire at a time and see what happens.

 

[johnlazelle]

Thanks, i will check that. I did replace the plugs and they were both clean so i would assume they were both sparking fine?

 

[Robert Ellis]

have you tried pumping the bulb as you open the throttle?

 

[F_R]

So, did you inspect the high speed orifice plug (jet) in the carburetor? It is in the very bottom of the carburetor bowl, behind the hex drain plug. It must be absolutely CLEAN without a trace of any gum, varnish , or crud in it.

The glass filter bowl normally runs mostly empty. That's just the way they are.

Pumping the squeeze bulb is a valid way of checking fuel delivery (pump) to the carburetor. But if you really want to test the actual function of the pump, invest in a fuel pressure test gage. They don't cost much, usually combined with a vacuum gage.

 

[johnlazelle]

So I got a new fuel pump, fresh gas and made sure tank was clean. Took it out on the lake and when it was cold, it ran perfect. Got up to 25 mph and was running smooth. When the engine got warmed up, it would no long Mac out. Would only get about 10-15 mph and felt like it was bogging down. Pulled one plug wire at a time and as soon as I did it would run rough or stall, so I think both cylinders are sparking fine. Coils, plugs, points, condensers and wires are new. Any suggestions or recommendations? I will check the carb float bowl high speed needle.

 

[johnlazelle]

So I got a new fuel pump, fresh gas and made sure tank was clean. Took it out on the lake and when it was cold, it ran perfect. Got up to 25 mph and was running smooth. When the engine got warmed up, it would no long Mac out. Would only get about 10-15 mph and felt like it was bogging down. Pulled one plug wire at a time and as soon as I did it would run rough or stall, so I think both cylinders are sparking fine. Coils, plugs, points, condensers and wires are new. Any suggestions or recommendations? I will check the carb float bowl high speed needle.

 

[Robert Ellis]

You mention pulling 1 plug at a time when it was bogging down. Did you also adjust the high speed needle? I find mine usually have to be turned in a little from the recommended initial setting (which if memory serves is 3/4 of a turn?)

 

[F_R]

There is no high speed needle. It has a fixed high speed jet which I mentioned earlier. But that doesn't mean your suggestion is incorrect. It could be running rich for some other reason. Is the gasket on the main nozzle? Choke open? Link & Sync correct? Carb not flooding over?

 

[johnlazelle]

Just took the carb back off and checked/cleaned everything. Everything looks fine and didn't see any dirt or crude anywhere. I do have another question though, should the ignition plate assembly be loose? It seems looser than i remember it being originally????