SP Type Carburetor
This information and method of adjustment applied to all models of the SP type of carburetor
Before adjusting the carburetor make sure that the trouble does not lie elsewhere, particularly examine the spark plup and breaker points to see that they are set correctly, and that the choke is in full, open position. To adjust carburetor proceed as follows:
First-Close main adjusting needle by turning to the right or up until the needle is seated (never force tightly against its seat), then open by turning to the left or down two complete turns.
Second–Close the by-pass or low speed adjusting needle until it is seated by turning to the right or in, then open by turning to the left or out one-half turn. Thus adjusted the engine should start and operate.
Third—Set throttle lever on steering column to operate engine at a speed equivalent to 25 miles per hour car speed (never race engine). Start engine and run until thoroughly warin.
Fourth-Retard the spark control lever fully. With the engine running approximately 25 miles per hour car speed, gradually turn the main adjusting needle to the right or up to a point where the engine slows down for want of fuel. When this point is reached stop and gradually turn in the reverse direction until that position is found where the engine runs free. This adjustment should be carefully made for gasoline economy cannot be obtained if the needle is allowed to pass over the point of sufficient fuel delivery to give good power and free running. Provision for maximum power is automatically supplied, so in adjusting set the main adjustment to rrot-ide for economical road performance.
Fifth– Close the throttle fully and with the spark still retarded, set throttle lever stop screw to run engine faster than is desired for normal idling speed. Now turn low speed adjusting needle gradually to the left or out, thinning the mixture, until a noticeable flutter or missing occurs. At this point turn in the reverse direction only to that position where the engine again fires evenly. Leave this adjustment at the position delivering just as thin a mixture as will properly idle the engine. Now carefully adjust the throttle lever stop screw to operate the engine at the desired idling speed.
The plain. tube carburetor used in regular production has several special features which are called to your attention.
All Models SP Type Carburetors are distinguished from types furnished heretofore by:
First – A pump well for the purpose of forcibly inducing a positive supply of fuel for acceleration.
Second-A metering pin or lift needle, the object of which is to provide an additional fuel supply for quick wartning and for maximum power requirements.
In operation the carburetor is fully automatic except that at partial choke positioni-as controlled through the manual choke control on dash-fuel metering is governed by the usual high and low adjustment needles.
If as in instances where in cleaning or at times when the carburetor is for any purpose dissembled, we call to your notice the importance of the correct setting of the lift needle. With the throttle closed and the choke full open there should be a minimum of .030 to.040 play between the adjustable nut on the needle and the fork of the lever. There should always be sufficient play between the levers coupling the choke cam and the needle lift lever to insure the seating of this needle.
DURANT MOTORS, Inc.
NEW YORK, NEW YORK