accelerator pump timing?

This is my first attempt of doing the adjustment. can anyone explain the whole free play thing. The only way I can get rid of the free play is by screwing in the screw all the way.

This is a simple adjustment that can take some time. I did it when my bike was new and recently checked it - slightly out.

If you have the manual it is on page 4-18.

To do it properly you have to loosen the carb so you can space the throttle slide at 3.1mm, then adjust the link.

The screw acts against a cam. In short:

1. Screw all the way in

2. use index finger (left) to pull against cam back towards the thread, you will feel a few mm of "slop"

3. Screw the adjsuter back out, this "slop" reduces

A picture is worth a thousand words so if you dont have the manaul there is a FREE pdf manual available for viewing OR download on the Aussie Yamaha website. I have it and makes for easy browsing....

If you cant find I have the page scanned and have sent it to TTers in the past - let me know.

Dial it in and it makes a difference...

Easy once done once


thanks a million will do.

What benifit do you achieve with this adjustment?

It is just what it says:

Accelerator pump timing adjustment:

Really it adjusts the START of the accelerator pump squirt. If you video the squirt, you can adjust the duration via leak jets and pump diaphrams, this AP timing adjustment changes the squirt start. Too slack (screw to far IN) and it occurs late.

Similarly, I assume you can probably advance the squirt, ie. occurs earlier in the throttle twist by turning the screw further out- that I have not tried so cannot verify!! I have not messed with it to that extent, but intuitively, this might give you less volume of squirt?? Anyone help on that? :crazy:

While the timing screw does adjust the start of the squirt, it also affects the end of the squirt, all else being equal.

The squirt has a duration, set by the diaphragm rivet and a volume, set by the leak jet, and to some degree, the rivet. The squirt will stop before the throttle reaches WOT, so if you increase the start delay, you also make the end of the squirt closer to WOT. Either way, you want your squirt to start as soon as possible without hitting the slide.

So, if your bog is at lower throttle positions, you probably need to tune it with leak jets, but if it's at higher throttle positions, you may need to shorten your diaphragm rivet because you've already used some of your pump stroke by that point, leaving you with less available squirt. I think this is where my problem was because I noticed a slight improvement with the Quickshot, which I measured at about .5 mm deeper than my stock cover, effectively increasing my pump stroke, similar to shortening the rivet.

What do you put under the throttle plate that is 3.1 mm's? is there a drill bit in standard size we can use?

Take a piece of heavy soldier, like plumbers use. Flatten it until its the right thickness. Use a set calipers to verify its thickness.

cool, great tip, I have some of that too, and some calipers, I found a 1/8 drill bit is just over 3.1 mm's I may try that also.

Thanks again guys, I tried to follow the manual and then i adjusted it a little more so that the squirt just clears the slide when accelerating fast, Hope for the best, will test ride it tomorrow to see how it is.

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