6 HP johnson idles pooley

I have a new to me 1968 Johnson 6 HP motor that starts easily, runs well, but at idle it dies after a few minutes.
Any ideas as to the cause?

kimcrwbr1 said:

Get a can of seafoam and add some into the fuel tank and the take it out and run it WOT for 1/2 an hour or so and see if it clears up the issue. Do you know the history on the motor how old are the plugs, impeller. When was it last run before you got it?

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The motor had been in storage for a long tine before I got it. It appears to have low hrs as it is very clean. As for the plugs they look to a little black, but not fouled when I pulled them out. I have no idea about the impeller.

Will it restart after you pump the squeeze bulb? Then maybe a problem with the fuel pump or tank/hose. Put the tank up above the level of the fuel pump and try it again. Gravity feed will provide enough fuel and we can then move forward to isolate the problem.

If it idles well for any length of time then dies, suspect the fuel pump as "TimGuy" mentions above, especially if pumping the fuel primer bulb (acting as a manual fuel pump) improves the running condition.

However, If returning the engine to idle results in having the engine die out rather quickly, the carburetor needs cleaning and rebuilding... a normal and usual problem due to having a engine sit for any great length of time.

(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.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1

I ruled out the fuel pump by running the motor with the gas tank elevated above the motor without any difference in performance.
I was able to vastly improve the idle by adjusting the S/S needle valve in about half a turn from the one and a half turns out starting point. At this point the engine generally idles OK with an occasional intermittent hiccup, can this be improved upon.

Remove the needle valve temporarily to inspect the taper of the pointed end.

If the taper is not perfect but rather it has a groove on one side, you might be able to grip the valve in a high speed drill or drill press and with a file, carefully refurbish that taper. If you attempt this, make sure to keep the angle of that taper true to specifications (as close as possible).

I checked the needle valve and it looked OK. After reinstalling and adjusting, it seems to idle acceptably well. thanks so much for your helpful advice.
Just out of curiosity, is the fuel pump, and carb. rebuilk still available for this motor, the Model no. is 6R-69M and the Serial No. is J3050689
Thanks,
Ed

Carburetor kit will always be available.

Fuel pump kit to my knowledge was never available... just replaceable.