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MrHonda, Motorcycle Mechanic
Category: Motorcycle
Satisfied Customers: 534
Experience:  40 years of Honda motorcycle ownership & repair. Author of the Classic Honda Buyer's Guide (MBI)
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How do I adjust the carburetor on a 2005 Honda CRF50

Resolved Question:

How do I adjust the carburetor on a 2005 Honda CRF50?
Submitted: 7 years ago.
Category: Motorcycle
Expert:  MrHonda replied 7 years ago.
What are you trying to "adjust"?

Idle speed adjustment is from the screw on the side of the throttle slide. It moves the slide up and down, opening and closing the amount of air going into the engine.

The screw toward the front of the carburetor is the idle mixture screw, which changes the amount of fuel/air at idle.

If the bike has been sitting for awhile with old gas in the carb/fuel tank, then the gasoline has either separated into alcohol/gasoline layers inside the float bowl or the gasoline has partially evaporated and some of the residues have plugged up the idle circuit jet, which does not appear to be replaceable from the illustrations. Careful cleaning of the carburetor body with carb cleaner and compressed air might restore that function again. A blocked idle jet will show up as an engine that is hard to start and wont' idle, even when hot.

You have to remove the carburetor and float bowl to access the main jet. If you have changed the air filter, exhaust system or changed the cam, etc. then the main jet will have to be changed to another size.

Bill S.
Customer: replied 7 years ago.
For both screws what is the initial starting point for adjustment? For example if fully closed is it 1 1/2 turns out, etc?

The bike has been sitting for quite a while, and the gas was not run out before storing. I'll definitely clean out the main jet, but just need the initial adjustments for the set screws as well.

The bike also has an added rev limiter chip (to remove the limits), and an after market pipe for better performance, if that matters.
Expert:  MrHonda replied 7 years ago.
The fuel screw should be out about 2 turns to begin with. The idle speed screw just raises the slide. If you can see the slide with air filter tube off, then watch it as you turn the screw in. Once the screw contacts the slide, you only need to turn the screw about 1/4 turn more to get the slide into a normal idle speed position.

You need to clean out the idle jet if you want the bike to start and idle. The main jet only feeds fuel mixture at 1/2 to full throttle...

Aftermarket pipe addition can cause the engine to run lean, so a larger than stock main jet MAY be in order.

Bill S.
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