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#7143
chstorm
Participant

Hi again Paul,

The setting of the pilot screw will vary from carburettor to carburettor. If the carburettor is worn, you will need a different setting than with a new carburettor. I would think that one turn out will be more correct than half a turn. However, you will need to experiment.
First of all, adjustment should be done with a warmed-up engine. If the exhaust is sooty (black), the pilot screw has been set too rich and should be unscrewed a bit.
If you start with the pilot jet one turn out from the bottom, you should now adjust the idling screw (the other screw) in or out until you reach a suitable idling speed.
This done, unscrew the pilot jet little by little. If the engine runs faster, unscrew slowly until it is starting to misfire. Then screw it inwards slowly until the engine begins to slow down. Then out again a little until it reaches higher speed again.
If engine speed is too fast now, adjust the idling screw back a little and test the pilot screw again.
The adjustment of the pilot jet is fairly important since it not only controls idl├»ng mixture, but also influences mixture at speed up to 1/8 throttle or even more. If you feel “a hole in the middle” when slowly accelerating, it may be caused by a too lean setting of the pilot jet.

Good luck! Adjustment of carburettors may be tricky, especially if they are a little worn – but adjusting modern fuel injection is much worse!

Kind regards,

Carl