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Another "D" type adjusting screw - AP timing

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Hi all. I am in the process of trying to correct the touchy throttle effect in my 2009 CRF 250X about which I posted previously. I recently removed the throttle cable cover from the carb and was greeted by another “D” type adjusting screw – for the AP timing adjustment. Honda also thoughtfully enclosed most of the screw and spring in a cylindrical metal housing, making access to it similar to the “D” type fuel screw, except the AP timing adjustment screw is much larger.

As I understand it, older bikes of this model had the throttle cable pull the AP actuating lever via a spring. The O ring mod or stronger spring reduced or prevented the delay in actuating the AP which was caused by a weak spring. Turning the adjusting screw clockwise increased the gap between the cable lever and AP actuating lever, which would increase the delay in actuating the AP and could increase the bog effect.

In the newer bikes, the situation is reversed; the throttle cable lever PUSHES the AP actuating lever. This eliminates the delay caused by the weak spring in the older bikes. It also makes for a very touchy throttle, in my case anyway. In the newer bikes, turning the adjusting screw clockwise would also increase the gap, but would decrease the delay in AP actuation because the throttle lever would then push the AP actuating lever earlier.

This is my understanding of the situation; please correct me if I have overlooked or misinterpreted something. I am in the process of attempting to correct the touchy throttle effect; I am installing an AP cover with an adjustable leak jet, since that has been reported to have solved the problem on some bikes. If that doesn't work, I will go back in and try to adjust the “D” AP timing screw, but it was already adjusted pretty far counter-clockwise (the stock gap is about .038”).

Two questions – does anyone know if Teflon grease would be OK for the carb air boots; and does anyone know if there is a socket to fit the “D” AP timing screw? Thanks.

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The '08 apump adjustment works the same way as the previous years: get a 1mm gap in the linkage as a starting point for start of the squirt.

Changing leak jets will change duration of the squirt.

You don't need any apump linkage mods on a '08 or later.

The accelerator pump only activates when you turn the throttle at a certain speed or faster. If you are having throttle control issues from closed throttle to partial throttle, that is not the apump; that is the nature of the bikes cam/carb/gearing.

You can get used the the throttle, or, go with a G2 throttle cam, which opens the throttle slower, making control much easier.

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The AP cover with the ALJ is an expensive leak jet, but since you have it already, fine. Set it to be a #40

The 1mm adjustment must be done with the throttle slide ALL THE WAY DOWN. This means you have to back off the idle speed intill the slide is down as far as it will go (you will see clearence at the idle speed screw/throttle wheel tab.)

Once you have the base timing adjustment set, ride the bike normally. If you have any bog, turn the AP screw CW 1/2 turn and retest. You will never get rid of a bog from idle to WOT, but no one does that anyways, right?

As far as the D driver, Motion Pro carries a few different ones. Do not grease the airboot to carb connection (I assume that is what you meant and not the filter).

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Do not grease the airboot to carb connection (I assume that is what you meant and not the filter).

Why no grease on the airboots? I did mine once and BOOM went right back on. I wiped it off next time I disassembled though. I got worried that some grease might have gotten into the slow air jet on my 06 X.

Also....what year bikes does the 1mm gap in the APscrew/arm apply to? I thought we wanted em wired with no gap at both closed throttle and WOT.



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Same reason the boot went on so easy, it comes off too easy! Actually, with a little thinking and less wrestliing, I find most boots actually pop on by themeselves just about. All about the alignment and pull on just the right place. Kind of freaky when you do it right.

I beleive the Honda was the same as the rest of the world for '06 and back. I have not touched nor seen the service manual for a new style pull FCR so I do not know the method to get a base timing adjustment (though I imagine it is the same). These are the two methods that I rec. for regular FCRs.

Resetting the AP timing to 'stock'

Method #1 - Most accurate

Turn the idle speed screw so the slide is completely closed (count the turns and note it) .

Turn the throttle wheel, raise the slide, slip a .8mm drill blank under the slide, release the throttle wheel, pinning the blank.

Turn the AP timing screw so the play just barely goes away.

Remove the drill blank, reset the idle speed to where it was.

Fine adjust the AP timing screw by test riding, turning in 1/2 turn increments to where the bog is just gone. Should be less than 2 turns, if at all.

Method #2 Not as accurate

Back out the idle speed knob (count the turns and note it) until the screw end of the idle speed cable is no longer touching the theottle wheel - Throttle cables may have to be fully lossened.

Ensure the slide has b;ttomed out; on the carb bore'

Set the timing gap between the cam and the screw to be .010"

Reset the idle speed per your notes, reset the throttle cables if loosened.

When you wire/oring/stiffer spring the linkage, you are pulling the pull rod up some. The spacing is still there, sort of.

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