Logo
FULL SITE MENU

1962 - 3 HP Johnson - Carb Problems

4

426hemi

Contributing Member
Hi all. I have a 1962 Johnson 3 HP (Model JW-17) that I use for trolling. It has a self-contained fuel tank on top of the engine that gravity feeds to the carb. The engine is old but has less than 100 hours on it. Compression is up to spec on both cylinders. It has always been stored indoors and, up to last fall, ran like a Swiss watch (nearly). At that time it started flooding out after running for a few seconds and gas would be dripping out of the air intake. My first thoughts were that an inlet valve being worn out or stuck open or a perforated float would be the culprit so I did the following:

Disassembled and cleaned the entire carb
Replaced the inlet valve, seat and the float
Replaced the high and low speed needle valves and packing and adjusted them 1.5 turns back out from being fully seated.
Choke mechanism was lubricated and moves smoothly.
New spark plugs installed.
Fresh gas used

Now the engine refuses to start and, after only two pulls on the starter rope, gas starts dripping out of the air intake again. I have adjusted the float level at least 6 times and I have pressure tested and determined that the inlet valve is both seating and opening properly. Nothing so far has solved the problem and I can't get so much as a cough out of the motor before the fuel starts dripping.

Any suggestions would be sincerely appreciated. :D I've run out of my own ideas. :eek:
 
Spark must be able to jump a gap of 1/4" or better.-------Remove recoil starter and remove inspection plate to have a look at the coils.
 
I assume the "inlet valve" you speak of is a "new" float needle valve assembly (rubber tipped needle, brass seat).

(Carburetor Float Setting)
(J. Reeves)

With the carburetor body held upside down, the float being viewed from the side, adjust the float so that the free end of the float (the end opposite the hinge pin) is ever so slightly higher (just ever so slightly off level) than the other end. And when viewed from the end, make sure it is not cocked.

Simply set the float in a container of water to get a idea of its buoyancy.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.
 
Is the filter inside the tank (directly above the fuel shut off valve) still in place? What Gas
/oil ratio are you using?
 
Just got back from a trip so I was unable to try any of the suggestions until today. I adjusted the float as per joereeves instructions and now it starts and runs great. It's usually the simplest things that cause me the most trouble - lol. Thanks again everyone!
 
Back
Top