knobs on carb 1963 johnson 40 hp

can anyone tell me what the knobs on carb do, one on left, and one on the right. the one on the right has some sort of linkage on it. the affect how the motor runs, my guess is fuel air mixture, but i would like to know how to dial them in

Re: knobs on carb 1963 johnson 40 hp

I don't have a view of your carb, but a guess is the linkage goes to the low speed needle valve (upper needle), the other one the high speed needle valve. You'll probably have to remove the linkage from the end of the low speed needle to make the adjustment and replace when done.

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, wating for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top 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. Again, 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 adjustments, 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.

Re: knobs on carb 1963 johnson 40 hp

Just finished rebuilding my carb on my 60' 40hp. The top one on the left is the low speed needle, the top right knob with linkage goes down to the high speed needle in the bottom of the bowl. If you take the screw out of the center of both needles the knobs will pull off of them allowing you to make the main adjustments beyond the stops. Once you get them to where you want them (as listed in the adjustment info posted above) put the knobs back on, but be sure to put them in the center of the adjustment range so you will be able to tweek it either dirction if needed.

Re: knobs on carb 1963 johnson 40 hp

Linkage goes to the high speed needle.