Originally posted by Baldy:
I would suggest that you hook up the hand throttle and adjust the idle with the engine warm and use the hand throttle to increase the cold idle; works for me.
I would concur with Baldy.
I cannot think of a single manual choke carburetor that is supposed to have the idle adjusted on a cold engine (although someone will probably find one just to prove me wrong
). This is also generally true with auto choke carburetors.
When adjusting the idle on a carburetor, start the engine and run at a fast idle until the engine is warmed to NORMAL OPERATING TEMPERATURE; then adjust the curb idle speed.
Fuel is not vaporised as efficiently in a cold engine; REQUIRING additional mixture to be present to maintain a "cold" idle. The idle circuit does not change from cold to hot; thus the extra mixture when hot (if set cold) would cause a higher engine RPM when hot.
Typically, 2 methods are employed to maintain a good idle when cold: (A) increasing the throttle opening (thus adding some fuel though the idle transition circuit) as suggested by Baldy; and (B), adding additional fuel through the use of the hand choke.
Since the atomization of fuel will increase on a cold engine with an increase in the ambient temperature, it may sometimes be difficult to obtain a "perfect" setting in temperatures of 70 degrees F or more. But a good rule of thumb would be that if an engine equiped with a manual choke carb IDLES WELL ON A COLD ENGINE WITH THE AMBIENT BELOW 50 DEGREES F. AND NO CHOKE OR HAND THROTTLE, then the idle is adjusted TOO RICH or too high.
Jon.
