Rich/Lean Knob

Joined
Jul 8, 2012
Messages
24
Hey guys,

I'm currently in the process of rebuilding a 1960 40hp Johnson. I was wondering if the rich/lean switch controls the high speed or low speed needle? I would assume it would control the low speed since it has to do with starting the engine and warming up but the linkage is so long that the only thing it could connect to is the high speed needle. thanks for your help guys.

Jason
 

Daviet

Fleet Admiral
Joined
Sep 24, 2008
Messages
8,958
Re: Rich/Lean Knob

There should be an adjustment for both the low and high speed needles.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Rich/Lean Knob

If that carburetor has but one adjustable needle valve (top), that would be a slow speed needle valve, BUT the 1960 40hp model carburetor has two adjustable needle valves.

What is the model number of that engine?
 
Joined
Jul 8, 2012
Messages
24
Re: Rich/Lean Knob

Joe the model number is RDS-22.

Bplayer thanks for the image. So if I understand correctly, once I have the high and low speed needles adjusted properly I just flip the switch to rich on cold starts and while the motor is warming up?
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Rich/Lean Knob

Joe the model number is RDS-22. So if I understand correctly, once I have the high and low speed needles adjusted properly I just flip the switch to rich on cold starts and while the motor is warming up?

No.... Once you have the carburetor adjusted properly, there should be no need to touch the adjustments again.

(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, waiting 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.
 
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