Linkert Carburetor Tuning for Side Valve Engines

 

Linkert carbs are a beautiful thing. Here are some general tuning tips to get you started.

1.  First, the carb is the last part of a motor you tune. Valve seating & adjustment, no leaks at intake manifold, good coil & condenser, breaker point setting, spark plug gap, timing and battery condition must be dead on.

2.  Check float level. Remove float bowl, turn bowl upside down, and check to see that float on opposite side from float valve is exactly 1/4" from top of float bowl. With float bowl upright, the float should also be installed approx 1/16" to the left of the center of the float bowl. There should be not more than .003" free play between float lever fingers and the needle valve. With float correctly installed in bowl, seal around screw holding float to lever with Indian Head Shellac (by Permatex at most auto parts stores).

3.  With chock open, gently screw down low speed needle to seat and back out 5 turns, which will probably be on the rich side. This low speed needle has a internal spring in knob, screw down only until needle hits seat, not beyond this point to compress spring (it will give you a false count on turns). Gentle screw down high speed needle to seat and back out 2 turns. (It is noted that stock M88 carbs do not have a high speed needle and have fixed jet with no high speed tuning, unless fixed jet has been removed and high speed needle installed). Low speed needle  is for smooth idling and the high speed needle is for high speed use.

4.  Start motor, set spark advance at full advance, and warm up. Set stop screw at throttle lever bracket on top of carb for idle speed. Verify that there are no intake manifold leaks, a common problem.

    Low Speed Needle: Adjust low speed needle first with motor at idle. Screw in low speed needle one notch at a time until motor starts to missing and acts starved, back out approx 5-10 notches. Motor should be running smoothly. Readjust idle speed with stop screw at throttle lever bracket if necessary (a slightly higher idle setting at throttle lever makes for easier starting). Make final adjustment at low speed needle. Try one notch at a time, screwing in or out, to see if motor runs smoother or idles faster. Always check adjustment on low speed needle after change of setting on throttle lever stop.

    High Speed Needle: With spark at 1/2 full advance, open throttle for fraction of second. If motor backfires or spits through carb, mixture is too lean. Back out high speed needle valve approx 1/2 turn. If motor chocks when throttle is opened for fraction of a second, the setting is too rich, back out high speed needle valve approx 1/2 turn. Repeat adjustments until satisfactory high speed needle adjustment is achieved. Back needle out another approx 4-5 notches and run bike up to approx 35 mph. If motor runs well when accelerating, screw needle in 1-2 notches. If it tries to spit or hesitate, back needle out 3-5 notches until motor is running clean.

 Always run low speed and high speed jets a little on the rich side, it makes for easier starting and a cooler running motor with no burnt pistons.

 

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