Carburettor idle adjustment advice needed

Foggy · 19-09-2024, 05:48 PM

I am seeking advice on idle speed adjustment for my carburettors on an M600. The bike was refusing to idle even when warm so, in an attempt to address the issue, I adjusted the screws located at the front and behind the carbs to approximately 2.5 turns out from their fully closed positions (after several attempts at other settings). However, this has led to the engine racing at several thousand rpm upon ignition.

In the past on other bikes I have started the engine and done the usual turn the screw clockwise until it gets lumpy then turn the screw anti clockwise until it gets lumpy then turn it back to the midway position of the two. But because of the high revs I am reluctant to leave it running so I switch it off meaning I need to do the adjustment “blind” without the engine running.

Could anybody please guide me on which adjustment screws need to be modified and by how much to obtain a normal tickover speed?

As an aside, is the front adjustment screw (by the air filter) for adjustment of air intake so clockwise makes it richer and is the rear adjustment screw for fuel intake so clockwise makes it leaner ? Or is the front screw just for air/fuel mixture and the rear for idle speed ?

19-09-2024, 05:48 PM	#1
Foggy Registered User Join Date: May 2024 Location: Diss Bike: M600 Posts: 32	Carburettor idle adjustment advice needed I am seeking advice on idle speed adjustment for my carburettors on an M600. The bike was refusing to idle even when warm so, in an attempt to address the issue, I adjusted the screws located at the front and behind the carbs to approximately 2.5 turns out from their fully closed positions (after several attempts at other settings). However, this has led to the engine racing at several thousand rpm upon ignition. In the past on other bikes I have started the engine and done the usual turn the screw clockwise until it gets lumpy then turn the screw anti clockwise until it gets lumpy then turn it back to the midway position of the two. But because of the high revs I am reluctant to leave it running so I switch it off meaning I need to do the adjustment “blind” without the engine running. Could anybody please guide me on which adjustment screws need to be modified and by how much to obtain a normal tickover speed? As an aside, is the front adjustment screw (by the air filter) for adjustment of air intake so clockwise makes it richer and is the rear adjustment screw for fuel intake so clockwise makes it leaner ? Or is the front screw just for air/fuel mixture and the rear for idle speed ?