JCL MP250A air/fuel mixture By pudntane (Read 1,781 times)

[pudntane]

Can someone PLEEEEEEZE tell me exactly where the mixture screw is located on my Keihin carb? I can't see anything on the left side where I had hoped it would be.

I replaced a defective enricher and now the carb is set too lean and wants to quit when the enricher disengages.

Thanks
Ernie

[Alleyoop]

How do you know it is running LEAN? It may just be Idleing to low once the ENRICHER cuts off the extra Fuel. If you have a tach on the scoot once the Enricher cuts off the extra fuel it should be IDLEING around 1500-1800 rpms. If not then Turn the IDLE SPEED SCREW the one with the SPRING on it on the Throttle Cable SIDE Clockwise a little to raise your IDLE.

But usually on the 250s they come with a 30mm or 32mm carb and the FUEL RATIO SCREW is in Front and Underneath.
Alleyoop

[ce]

Loosen the clamps holding the carb to the intake and the manifold and turn the carb itself about a quarter turn to bring the bottom of the carb into view.

The carb drain will be at the back, and in the middle of the front side of the bottom of the carb, you will see a brass screw all by itself. Turn it a half turn counterclockwise to richen the mix, center the carb and tighten the clamps and test the idle.

That's only if your certain the idle speed screw is already set to idle at 2000 RPMs, which if it isn't may be what your ilde problem is anyway.

The Chinese reccomend 1500 to 1800 idle speed, but those are Chinolutions Per Minute, and here in the USA we need to beef that up to 2000 or the engine dies a lot.

[Alleyoop]

You do not need to loosen and or turn the carb sideways to adjust your fuel ratio screw:
Use one of these Interchangeable screwdriver tips to get at the Fuel Ratio Screw.
Alleyoop

[pudntane]

Aug 19, 2011 14:41:54 GMT -6 Alleyoop said:

How do you know it is running LEAN? It may just be Idleing to low once the ENRICHER cuts off the extra Fuel. If you have a tach on the scoot once the Enricher cuts off the extra fuel it should be IDLEING around 1500-1800 rpms. If not then Turn the IDLE SPEED SCREW the one with the SPRING on it on the Throttle Cable SIDE Clockwise a little to raise your IDLE.

But usually on the 250s they come with a 30mm or 32mm carb and the FUEL RATIO SCREW is in Front and Underneath.
Alleyoop

The scooter was always hard to start but it ran half decently. After inspecting the enricher, I found it to be stuck all the way out and defective. After replacing the enricher, the scooter was really hard to start and stalled when I came to a stop unless I gave it a little throttle. Hence, the Chinese must have set the mix with the defective enricher slammed all the way into the venturi.

I am taking it to a scooter dealer because I've had it! He may charge me up the wazoo but I don't care at this point if he makes it right. I told hime to adjust the valves as well.

Thanks for the great advice and the terrific carb drawings.

Ernie