Re: 88 Johnson 20hp - I'm about to give up.....
Full spark advance timing...... Even is adjusted incorrectly, that would not cause the dying out problem that you have BUT it would result in internal damage (preignition, etc). The full spark advance stop is the rubber bumper on the long screw that has a lock nut that prevents it from turning..... the timer base under the flywheel would be right up against it when at the full throttle/full spark setting. It can be checked/adjusted as follows.
(Timing At Cranking Speed 4?)
(J. Reeves)
NOTE: If your engine has the "Fast Start" feature", you must disconnect/eliminate that feature in order to use the following method. The "Fast Start" automatically advances the spark electronically when the engine first starts, dropping it to normal when the engine reaches a certain temperture.
The full spark advance can be adjusted without have the engine running at near full throttle as follows.
To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).
Rig a spark tester and have the gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4? less than what the engine calls for.
I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28?, set the timing at 24?. The reasoning for the 4? difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4?.
If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4? which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.
No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.
Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes.
Throttle butterfly engagement...... Look closely at the cam on the timer base, the casting that rubs against the throttle roller. You'll see two marks on it. The throttle butterfly should just start to open when those two marks are dead center with the throttle roller..... not before or after. If the butterfly opens too soon in relation to the timing (those two marks), the engine will surely bog down. Also double check to make sure that the throttle butterfly does not pass the full throttle horizontal position when at the full throttle setting.
Carburetor kit..... The small circular nozzle gasket on that 1988 20hp model should be the same thickness as the float chamber to upper body gasket, NOT a thick cork gasket. If you have the thick cork gasket, you have the wrong kit.
(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.
(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.
Note 1: As a final double check setting of the slow speed valve(s), if the engine has more than one carburetor, do not attempt to gradually adjust all of the valves/carburetors at the same time. Do one at a time until you hit the above response (die out or spit back), then go on to the next valve/carburetor. It may be necessary to back out "all" of the slow speed adjustable needle valves 1/8 turn before doing this final adjustment due to the fact that one of the valves might be initially set ever so slightly lean.
Note 2: If the engine should be a three (3) cylinder engine with three (3) carburetors, start the adjustment sequence with the center carburetor.
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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