MTD P90 series Shop Manual page 46

P90 Series Vertical Shaft Engines
NOTE: The pilot screw regulates how much of this
pre-mixed fuel/air emulsion is allowed to
enter the throat of the carburetor, to atomize
down-stream of the throttle plate. On current
production units, it is set at the factory and
the screw head is removed.
See Figure 4.14.
NOTE: The transition ports are fixed. They are
drilled into the throat of the carburetor,
down-stream of the venturi. They lie behind
the brass welch plug near the pilot screw.
10. Soak the Carburetor body in a suitable solvent until
clean.
NOTE: Ultrasonic cleaning using a suitable water/
detergent mixture will clean carburetors
safely and effectively.
11. Rinse it thoroughly.
12. Dry the carburetor body using compressed air.
13. Reassemble the carburetor and install it by following steps 1-8 in reverse order.
14. Start the engine and check the idle RPM using a tachometer.
15. Check the top no load speed of the engine.
NOTE: The top no-load speed of the engine is 3300 RPM's + 100.
16. Adjust the engine speed as needed by following the procedures described in the speed adjustment section of
this chapter.
17. Test run the engine before returning it to service.
40
Transition ports Pilot port
Pilot screw
(before head
Figure 4.14
is removed)