Re: Johnson v-4 low speed problems
Old_Head.... Each carburetor on that model has adjustable slow speed needle valves, one for each cylinder.<br /><br />There is a nylon retainer/bushing at the very front of the carburetor where the needle valve enters. The original retainers were clear or black, both colors of which would not retain the needle valve firmly.... the needle could rotate due to engine viberation. The proper retainer to use is RED in color and will grip the needle valve so firmly that there is no need for the original interlocking linkages that tie the four valves together. This RED retainer is OMC part # 315232.<br /><br />The carburetor adjustment are touchy, pertaining to getting the slow speed needle valves set properly. The following instructions should be followed and performed one carburetor and one needle valve at a time ie Top Carb, Left Needle Valve first..... then Top Carb, Right Needle Valve, then to the bottom carb etc etc. If you attampt to adjust all four a little at a time, it gets really confusing and one loses track of what one did two minutes ago.<br /><br />Hopefully the following may cure your idle problems.... or at least help it somewhat.<br /><br /> (Dual Carb V/4 With 4 (2 each carb) Slow Speed Adjustable N/Valves)<br />The adjustment procedure of the carburetor slow speed needle valves follows. NOTE... if the needle valves turn too freely, replace the nylon bearing retainer (the nylon item at the front of the carb that the needle valve goes through first) with the newer type RED retainer #315232. If your engine has that weird linkage that connects all four of those needle valves, the newer RED retainers will enable you to discard that linkage. The RED retainers make it impossible for the needle valves to viberate out of adjustment. <br /><br />(Carburetor Adjustment - 2 Slow Speed Adjustable Needle Valves, each carburetor) <br /><br />Initial setting is: All (4) Slow speed valves = seat gently, then open 1-1/2 turns. <br /><br />Facing the carburetors, start with the top left needle valve, then the top right valve, then the bottom let valve, then the bottom right valve. It may be necessary to redo these steps to get the adjustments ideally set <br /><br />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. <br /><br />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. <br /><br />Do not attempt to gradually adjust all four of the valves 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. <br /><br />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.
