Re: Idling issue. Still not solved. Getting frustrated. 1961 40hp Johnson RDSL-23
Keeping in mind that you have a engine that is going on 53 years of age.
How long have you owned this engine?... Did it ever run normally?... Has it been sitting for quite awhile since it last ran normally?
What are the compression readings of each cylinder?... With the spark plugs removed, does the spark jump a 1/4" gap with a strong blue lightning like flame, a real SNAP?
NOTE:
Opening the choke... means that the choke butterfly is horizontal and no extra fuel is being pulled into the engine.
Closing the choke... means that the choke butterfly is vertical, closing off the carburetor throat, forcing the engine to draw in more fuel.
If the compression is okay, and the spark appears to be okay, the usual causes you explain could be, just to name a few:
1 - A wobbling armature plate under the flywheel. This would result in having the points change their gap (normally .020) as the timing is advanced. (see below)
2 - Wrong spark plugs... should be either Champion J4C or J6C plugs, gaped at .030.
3 - Carburetor fouled, gummed, clogged. (If sitting a long time, clean and rebuild)
4 - Carburetor adjustable needle valves set wrong. (see below)
5 - Broken diaphragm in the fuel pump.
(Magneto Armature Plate)
(J. Reeves)
If the armature plate has a a loose fitting, wobbling motion (the plate that the points, coils etc are attached to), it is usually caused by a slightly worn support ring. This allows the point setting to change erratically as the armature plate turns.
The cure is to remove the armature plate so that the support which is attached to the powerhead with 4 screws is visible. Then, with a screwdriver and hammer, or some tool of your choosing, and looking straight down at the support ring, make a slight indentation at what would be called the 12, 3, 6, and 9 O'clock positions. Install the armature plate and check for a smooth turning wobble free movement.
You may need to do that procedure a few times to obtain the proper fit (not too tight, not too loose), but it's worth the effort.
Use a small amount of anti corrosive grease between the aluminum ring and the brass support plate and also on the brass bushing of the armature plate when all is well.
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Depending on which carburetor you have on that engine:
(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.
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(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.