How To Adjust Idle On Johnson 50hp With Fixed High And Low Needles

Our friend and longtime OMC Tech, Joe Reeves, has posted thousands of answers to technical questions about Johnson and Evinrude motors on our Boat Repair Forum. He started contributing to the forum in 2001 and is withal at information technology! He has helped endless visitors solve their engine problems. We have compiled some of his Carburetor adjustment posts here.

(Carburetor Adjustment – Single S/S Adaptable Needle Valve)
(J. Reeves)

Carburetor_Single_Slow_Speed_Needle_Valve

Initial setting is: Irksome speed = seat gently, then open i-ane/two turns.

Start engine and set the rpms to where information technology simply stays running. In segments of i/8 turns, start to plough the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms volition increase. Lower the rpms once again to where the engine will but stay running.

Eventually you'll striking the indicate where the engine wants to die out or information technology volition spit back (sounds similar a balmy backfire). At that betoken, dorsum out the valve 1/four turn. Inside that 1/4 turn, yous'll notice the smoothest tedious speed setting.

Notation 1: As a final double check setting of the slow speed valve(south), if the engine has more than 1 carburetor, do non attempt to gradually adjust all of the valves/carburetors at the same time. Exercise one at a fourth dimension until you hit the in a higher place 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 i/8 turn earlier doing this final adjustment due to the fact that 1 of the valves might exist initially set ever and then slightly lean.

Notation ii: If the engine should exist a three (iii) cylinder engine with 3 (iii) carburetors, start the adjustment sequence with the heart carburetor.

When you have finished the above adjustment, you lot volition accept no reason to movement them again unless the carburetor fouls/gums upwards from sitting, in which case y'all would be required to remove, clean, and rebuild the carburetor anyway.

(Carburetor Adjustments – 2 Adjustable N/Vs)
(J. Reeves)

Carburetor_Two_Adjustable_Needle_Valves

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

Setting the loftier and depression needle valves properly:

Notation: For engines that DO NOT have a shift selection, plain at that place is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve aligning.

(Loftier Speed) Start engine (it volition run pretty rough), shift into forward gear, have up to total throttle. In segments of i/8 plow, waiting for the engine to respond between turns, outset turning in the bottom loftier speed needle valve. You'll achieve 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/four plow, yous'll find the smoothest setting.

(Low Speed) Slow the engine downwardly to where it merely stays running. Shift into neutral. Again in segments of 1/viii turns, kickoff to turn the meridian needle valve in. Wait a few seconds for the engine to answer. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually y'all'll hit the point where the engine wants to die out or information technology will spit back. Again, at that point, back out the valve one/4 turn. Within that ane/iv plough, you lot'll find the smoothest tedious speed setting.

When you accept finished the above adjustments, you volition have no reason `to move them over again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

(Dual Carb V/4 With iv (2 each carb) Boring Speed Adjustable N/Valves)
(J. Reeves)

Dual_Carburetor_V4_Two_SS_Needle_Valves_Each

The adjustment process of the carburetor slow speed needle valves follows. NOTE… if the needle valves turn too freely, replace the nylon begetting retainer (the nylon item at the front of the carb that the needle valve goes through first) with the newer type Cerise retainer #315232. If your engine has that weird linkage that connects all four of those needle valves, the newer Carmine retainers will enable you to discard that linkage. The RED retainers make information technology impossible for the needle valves to vibrate out of adjustment.

(Carburetor Adjustment – 2 Ho-hum Speed Adjustable Needle Valves, each carburetor)

Initial setting is: All (4) Irksome speed valves = seat gently, so open ane-1/two turns.

Facing the carburetors, commencement with the elevation left needle valve, then the summit correct valve, then the lesser permit valve, then the bottom correct valve. It may be necessary to redo these steps to get the adjustments ideally ready

First engine and fix the rpms to where it simply stays running. In segments of 1/8 turns, kickoff to turn the S/Due south needle valve in. Wait a few seconds for the engine to respond. Equally you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will only stay running.

Eventually you'll hit the signal where the engine wants to dice out or it will spit dorsum (sounds like a mild backlash). At that point, dorsum out the valve 1/4 turn. Inside that 1/4 turn, y'all'll find the smoothest dull speed setting.

Do not attempt to gradually adjust all four of the valves at the same time. Practice one at a time until you hit the in a higher place response (die out or spit back), then go on to the next valve.

When you have finished the above aligning, yous will have no reason to move them once more unless the carburetor fouls/gums up from sitting, in which case yous would be required to remove, clean, and rebuild the carburetor anyway.

(Carburetor Adjustments – Older Five/iv Downdraft Carb)
(J. Reeves)

Older_V4_Downdraft_Carburetors

Annotation: The early on model downdraft carburetors incorporated "Adaptable High Speed Jets". The later model downdraft carburetors used "Stock-still High Speed Jets". The loftier speed jets would be located in dorsum of the two bottom drain screws. Follow the beneath instructions accordingly.

Annotation: If you practice not have adjustable loftier speed jets, ignore those paragraphs pertaining to same…… Only exercise brand certain that you manually audit and make clean the 2 brass fixed high speed jets which would be located in back of the ii vii/16″ slotted hex head bolts in the bottom forepart portion of the float chamber.

Lift the center High Speed Command lever and turn it and so that the signal faces forward, resting on the high ridge. This will undo the lever control gear from the individual loftier speed jets (slots). Take the slow speed needle valve knobs installed upside downwards and so that they can be turned without encountering any obstruction.

Gently seat each of the High Speed needle valves, then back each one out one (1) plow. Gently seat each of the Ho-hum Speed needle valves, then dorsum each ane out one and one one-half (1-1/ii) turns. Annotation… have the jam nut on the s/speed needles snug so that vibration won't have whatever effect on them, but loose enough so that yous can turn them without a peachy amount of effort.

(High Speed)

With a reliable person at the wheel, and 1 kneeling in forepart of the engine, start the engine (yeah, it will run lousy with the above initial needle valve settings), put information technology into forward gear, and employ full throttle. Kickoff with the Loftier Speed aligning on the left using a screwdriver that properly fits the slot.

(Loftier Speed Adjustments)
At full throttle, with the proper size screwdriver, slowly start turning 1 of the H/S needles in segments of 1/8 plough, waiting momentarily for the engine to respond, and then repeat turning. Yous will reach a point where the engine will showtime to die out. At that point, back that needle valve out approximately 1/4 turn. Now, go to the other High Speed needle valve and repeat that procedure. At some indicate in that i/4 turn out, yous volition find the smoothest high speed setting (you can at present lower the throttle rpm). That volition have both high speed needle valves prepare correctly, and at that bespeak y'all can elevator that eye lever adjustment of that high ridge, keeping it lifted until the indicate is facing the engine, then lower information technology into its proper position. (When you turn that lever now, you're adjusting both High Speed needle valves at the aforementioned time.)

(Tiresome Speed Adjustments)
At present, lowering the rpms of course, take the engine out of gear and fix the throttle just to where the engine will stay running. Once more, in segments of 1/viii turn, slowly starting time turning in one of the irksome speed needle valves, waiting a few seconds between each turning for the engine to answer. As you lot plow the due south/speed needles in, the rpms will increase….. and every bit it does, lower the rpms to where the engine will just stay running (otherwise the rpms will climb quite high). You will reach a point whereas the engine will either outset to die out or it will spit dorsum (sounds similar a balmy backfire). At that point, back the needle valve out 1/four turn. Repeat the process with the remaining slow speed needle. Again, at some point in that 1/4 turn out, you volition discover the smoothest setting. When finished, tighten the jam nut somewhat, then remove and reinstall the s/speed knobs correctly (correct side up).

Editor's note: Delight too refer to your specific engine diagrams and a Service / Repair Manual for your model for additional information.

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