Dies with Quick Throttle-Up!

Gentlemen,

My bike will hesitate or even die with a quick throttle-up from idle. It starting doing this about 4 hours into a 6 hour ride. It doesn't seem to matter what altitude I'm at, as it did it at 11,000ft on the mountain and at the house at 4500ft. I removed the carb and cleaned it up, didn't really find a smoking gun. The accelerator pump appears to be working, although it may be weak? I tried two different spark plugs... I know that's probably not it, but ya know I was there and had one so what the heck.

2006 YZ450F

Power-Now

Red Beard Mod

Aftermarket Accelerator Pump (red it color)

Do you think the accelerator pump has gotten weak? The Red Beard Mod is hard on pumps, right? If I ease the throttle it will accelerate and has great power. Its just a snap acceleration from idle that will kill it.

-Joshua

No idea. Mine started doing the same thing today. Feels like a carb issue though. If u figure it out let me know

I pulled the bottom half of the carb bowl off, and removed the accelerator pump. It says "Factory Red" on the side, is that stock? The diaphragm and o-rings appear to be in good shape. All the passages are clear and I shot them with carb cleaner. The little check valve that allows fuel in seems to be working and the tiny "leak" jet is clear. However, it seems that there is no check valve operation occurring on the output of the pump. Is that check valve located further up the carb, or is it in the bowl that I removed?

Is just dawned on me that my accelerator pump has no spring! Is there an aftermarket AP that has no spring? Either way, the spring is not the problem as it ran fine before.

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