AP Squirt help

07 YZ450

So I did all the research on here and I still have a question.


Land off of a jump with the throttle shut off and it bogs and I almost

flip over the bars. So have to remember to have the gas ON when landing

every time.

So I performed the O-ring mod and adjusted the fuel screw multiple times.

(Everything is stock on the bike btw)

Still no improvement.

So now I'm trying to adjust the squirt, however no matter what I do

I can't make the squirt come out early enough to even hit the slide??

To get the squirt as close to the slide as possible, I had to back the screw

almost all the way out. Now this is contradictory to what I have read on here. Clockwise for earlier squirt....

Can someone give me some clues?

Get fuel injection......................... Ha have a good vacation!

Get fuel injection......................... Ha have a good vacation!


Ok I just figured out the screw is for the duration, not the timing of

by playing with it some more.

All the way in squirt was way short and late; all the way out the squirt

was right, about 1 sec. and very close to hitting the slide.

It's not supposed to hit the slide, and a full second sounds a little long. Check the condition of the diaphragm and the check valves in the cover.

But let me also point out that there's no way you should be landing a four-stroke off any kind of long air time with the throttle off and expect it to be different from landing with your foot on the brake. The engine will nearly stop the rear wheel in the air, and it needs to bring the rear wheel back at least up to speed before you land or you will be pushed forward on the bars. This shouldn't need any kind of instant acceleration from the engine to accomplish, either, just timing and control on your part. They are a lot different than two-strokes.

OK, thanks Gray. I will check the diaphragm and clean out the valves.

I figure I may as well put a new diaphragm in while I have it apart.

Why are there (3) models to choose from? I suppose I'll just get the standard

one unless someone could tell me otherwise.


,AP 1210410

(1485088-001) $28.28


,STD 1210411

(936429-001) $28.28


,AP 1210412

(936430-001) $28.28

I don't know whose part numbers those are, but they aren't Yamaha's

The standard diaphragm is 5JG-14940-17-00, and the alternates are 5JG-14940-18-00 and 5JG-14940-16-00. The difference is the length of the button on the bottom. The button length controls the length of the pump stroke and thereby the volume delivered during the stroke.

The 16 has a shorter button and therefore a longer stroke/squirt duration than the standard 17, while the 18 has a longer button, and a shorter stroke.

This info is posted in the Common Threads Sticky.

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