Yamaha WR45OFR service manual Examples of carburetor setting depending on symptom

SETTING

Examples of carburetor setting depending on symptom

T U N

	Symptom	Setting		Checking
At full throttle		Increase main jet calibration no.	Discoloration of spark plug →
Hard breathing		(Gradually)	If tan color, it is in good condition.
Shearing noise			If cannot be corrected:
Whitish spark plug			Clogged float valve seat
			Clogged fuel hose
Lean mixture
			Clogged fuel cock
			Check that the accelerator pump oper-
			ates smoothly.
At full throttle		Decrease main jet calibration no.	Discoloration of spark plug →
Speed pick-up stops		(Gradually)	If tan color, it is in good condition.
Slow speed pick-up			If cannot be corrected:
Slow response			Clogged air cleaner
Sooty spark plug			Fuel overflow from carburetor
Rich mixture
Lean mixture		Lower jet needle clip position.	Groobe 1
		(1 groove down)	Groobe 2
					Clip
			Groobe 3			Leaner
			Groobe 4
Rich mixture		Raise jet needle clip position.
			Groobe 6			↑
			Groobe 5
		(1 groove up)	Groobe 7			(Standard)
1/4 ~ 3/4 throttle		Lower jet needle clip position.				↓
						Richer
Hard breathing		(1 groove down)	Jet needle
Lack of speed
			The clip position is the jet needle
1/4 ~ 1/2 throttle		Raise jet needle clip position.
Slow speed pick-up		(1 groove up)	groove on which the clip is installed.
Poor acceleration			The positions are numbered from the
			top.
			Check that the accelerator pump oper-
			ates smoothly (except for rich mixture
			symptom).
Closed to 1/4 throttle		Use jet needle with a smaller diameter.	Slow-speed-circuit passage
Hard breathing			Clogged → Clean.
Speed down			Overflow from carburetor
Closed to 1/4 throttle		Use jet needle with a larger diameter.
Poor acceleration		Raise jet needle clip position. (1 groove
		up)
Poor response in the low to		Raise jet needle clip position.
intermediate speeds		If this has no effect, lower the jet needle
		clip position.
Poor response when throttle		Check overall settings.	Check air cleaner for fouling.
is opened quickly		Use main jet with a lower calibration no.
		Raise jet needle clip position.
		(1 groove up)
		If these have no effect, use a main jet	Check that the accelerator pump oper-
		with a higher calibration no. and lower	ates smoothly.
		the jet needle clip position.

*This should be taken simply for an example. It is necessary to set the carburetor while checking the operating conditions of the engine.

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