In extremely low temperatures it is wise to partially cover the radiator so as to maintain a temperature of from 175 Deg to 190 Deg bin the engine cooling system.
This will be found to increase the efficiency of the engine as a whole and will always result in more economical and more flexible action. In case a quick starting
away is necessary partial closing of the Strangler Valve will provide the necessary richness of mixture and this may then be released when the engine has attained
a temperature where the vaporization of fuel is possible. However, if the normal running temperature has been reached and trouble still persists, it may be due to the following causes:
Idling Mixture Too Rich
This will result in an accumulation of raw fuel in the gas passages and Carburetor. Opening the Throttle will cause this to be drawn up into the cylinders and will momentarily
enrichen the mixture to a point where it will not explode. Careful speeding up of the motor will usually carry this away, but the obvious remedy is to screw out on the
Idling Adjusting Screw, this "leaning" the mixture. This same condition may be caused by unsufficient hot air supply, particularly where the manifold diameter is
greater than that of the Carburetor, or where the manifold has rough inner walls.
In the former case, close the Temperature Regulator, should it be open, and if not, increase the volume of the hot air supply by fitting a larger stove. The hot air stove should
always be in a protected position on the exhaust pipe. If it should be in the path of the cold wind its efficiency will be correspondingly reduced.
Jets Too Small:
Try a larger size Compensating Jet.
If the Carburetor is adjusted to give too lean a mixture the engine will hesitate, spit back or stop altogether when the throttle is quickly opened after running at a low speed. In this case try a larger main jet. (Note: on some engines, due to varying characteristics of timing, manifold size or design, valve size, gas passage size and design etc., the Main Jet will exert a determining influence over this point of operation; in other cases the Compensating Jet will be the one. Therefore try one then the other, selecting, of course, the size Main Jet or Compensator most satisfactory. Try also increasing the heating)
If the Carburetor is adjusted to give too rich a mixture the engine will hesitate, and then run in an irregular manner when the throttle is quickly opened after running at a low speed. In this case put in smaller Main Jet or Compensator. (See note above)
If varying the jet sizes does not accomplish satisfactory results put in a smaller size Choke Tube, selecting jets accordingly.
Assuming that the Carburetor is of the correct size for the engine it may be said that if the manifold is of a larger inside diameter than the Carburetor that considerable difficulty may be experienced in obtaining satisfactory "quick throttle" action. In this case supply all the heat possible as it will tend to counteract the bad effects of the large Manifold.