Simple logical carb question.

84 HONDA XL250R. 1st: if nothing else were changed, one size larger pilot jet should cause the idle rpm's to increase, correct? 2nd: were the old 80's xl's known to be lean or rich from the factory?

Dont quote me but I think it would go up. Mainly would depend on the air screw setting previous to the change.

as duffy stated it COULD go up depending on factory fuel screw settings (readjust when done)

84 HONDA XL250R. 1st: if nothing else were changed, one size larger pilot jet should cause the idle rpm's to increase, correct? 2nd: were the old 80's xl's known to be lean or rich from the factory?

Not always.

If the screw is between the float bowl and cylinder, it's an air screw.

If the screw is between the float bowl and airbox, it's a fuel screw.

Typically, Honda 4-strokes have fuel screws.

If the fuel screw has no affect on the idle speed, the pilot jet is the wrong size.

Unless the pilot jet is clogged up. The new ethanol gas is nasty.

Here is a write up on how to adjust the fuel screw for the XR400.

It works the same way on any bike.

http://www.thumpertalk.com/forum/showthread.php?p=757112#post757112

Adjusting the Fuel Screw

The fuel screw is the fine adjustment for the pilot jet circutry. It should cover the adjustment needed between two jet sizes.

First, see how many turns it takes to fully screw in the fuel screw.

Write the setting down and reset the fuel screw to the original position.

Warm up the bike and let the bike idle.

Slowly turn the fuel screw, searching for maximum engine RPM.

Turn it slowly until the idle reaches peak rpm.

Turn the fuel screw out 1/8 extra.

If you get no change in RPM in the range of 1/2 to 3 full turns out, you probably need another pilot jet size.

WARNING: It is hard not to burn your hand doing this adjustment. I wear brown heavy cotton work gloves, though all leather gloves would be better. My hand still gets toasty. Do not wear riding gloves as the spandex and nylon parts will melt. Also, for CA models, I unbolt the crankcase canister, but don't always disconnect it. Often I can simply push it aside and turn the fuel screw.

were the 80s xl's generally rich or lean from the factory?

were the 80s xl's generally rich or lean from the factory?

Lean. All Hondas come lean.

Your backwards on that Kev. Cylinder side is fuel screw and airbox side is air screw.

Your backwards on that Kev. Cylinder side is fuel screw and airbox side is air screw.

Ooops! Thanks for the correction.

here is the better question, why or what problems or how do you think you know you need a jetting change???

The pilot was pretty spot on. The bikes are corked up from the factory from the airbox to the exhaust. Once you start to open that up, then you will need to work on the jetting a bit.

check me if im wrong sandy, but there is no fuel screw adjustment on the xl models due to the cap on the adjustment screw correct?

its on the side of the carb

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