Re: 4 hp Johnson 71 adjust carburator
Matrix,<br />Welcome to the forum.<br /><br />Carburetor Adjustments - Two Adjustable N/Vs)<br /><br />Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow<br />speed = seat gently, then open 1-1/2 turns.<br /><br />Setting the high and low needle valves properly:<br /><br />NOTE: For engines that DO NOT have a shift selection, obviously there is no<br />NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low<br />speed needle valve adjustment.<br /><br />(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to<br />full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns,<br />start turning in the bottom high speed needle valve. You'll reach a point whereas the<br />engine will either start to die out or spit back (sounds like a mild backfire). At that<br />point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the<br />smoothest setting.<br /><br />(Low Speed) Slow the engine down to where it just stays running. Shift into neutral.<br />Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few<br />seconds for the engine to respond. As you turn the valve in, the rpms will increase.<br />Lower the rpms again to where the engine will just stay running. Eventually you'll hit<br />the point where the engine wants to die out or it will spit back. Again, at that point,<br />back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed<br />setting.<br /><br />When you have finished the above adjustments, you will have no reason to move<br />them again unless the carburetor fouls/gums up from sitting, in which case you<br />would be required to remove, clean, and rebuild the carburetor anyway.
