ACP timing

Iam going to suggest that the start of the squirt should start as soon as you begin to twist the throttle, even if it hits the slide. My reason for this is : so what if it hits the still gets to the intake valve...the intake does not care how it is presented (nice clean squirt or yucky dribble)

Any Keihin experts out there care to set me straight ?

The less delay I have (screwed start ACP screw all the way out) the better the response seems to be off the bottom.

Comments ?

What, no Keihin experts in here ? :)


Hi Gary !! Seems like a good workaround to the BK mod as starting it early or prematurely would mean that less of it makes it's way into the intake ? What do you think ? I may be inclined to give this a try.

But, wouldn't reducing the squirt time be better as it means less fuel wasteage ? In the course of a days riding, twisting the throttle on and off a hundred times, could this represent signifcant fuel savings ?? Anyone ??

Nibble - I use the BK mod as well....Right now its set for +- 1 second...all the fuel should make its way to the intake.

I think your riding altitude (elevation) and year of your bike are the deciding factors. I have an '01 520 MXC in Colorado (5000'-10,000' riding elevations) with the FCR39. The best setting for me was to delay the squirt and shorten its duration - but then every new bike comes too rich here.


Your suggestion is open for debate.

Some riders contend that no delay at all is the ideal setup, even if it hits the slide. Others feel a slight delay is best to avoid squirts undesired at slight throttle movements near idle.

I find that the earlier it pumps helps snap the throttle and that's good when you ride hard in more open terrain. The slight delay is better when going slower and trying to finesse in tight woods where the bike can load-up and get too rich. A riders' style, skill level, and preference are the determining factors. The difference is slight between the two and most riders would find it hard to tell the setups apart.

The end result is that I make a compromise and set it up to keep a small delay, almost hitting the slide.


Am I mistaken? - doesn't the AP squirt go out the back of the carb toward the air box? Seems like thats what happened when I squirted myself in the face the 1st time when I was adjusting it??? :)

You are mistaken, it squirts towards the engine.

Gee, I hope that I didn't put the carb back on my bike backwards - no wonder I'm getting such good gas mileage! :)

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