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johnnyk52

All of you with a bike that will not idle

12 posts in this topic

Hey guys new here to this forum. After a lot of $ and a lot of time trying to determine why my 99 Wr400 wouldn't idle without the choke on I found the problem: accelerator pump diaphragm was cracked. I was leaking a bit of gas out the top of the pump where the rod goes in but never would have thought the accelerator pump would have anything to do with the idle.

After 2 carb cleanings, a new coil and countless other things I tried I put a new one in and it fired right up and idled great. Hope this helps.

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My 02s getting older good to know that in case it happens to me or one of my buddies .:banghead:

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It DOES help! My 99 is leaking right now and idling screwy. Did you order OEM parts or ??. O-rings too? . I need to get mine ordered.

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AZWFO: I went on bikebandit.com and ordered the stock diaphragm, spring, and two o-rings. I essentially re-built the accelerator pump.

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Don't forget to change the O-rings on the float needle seat as well. They dry up and start leaking for a flooded condition. WR Dave

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OK Yes, when i replaced the needle seat and o-rings and cleaned my carb, it made a huge difference. like 25-30% more power. like getting a new bike:thumbsup:

But the AP is bad, it idles high for 3-7 seconds after a rev comming to idle, but once it does idle , all is good. so again which AP diaphragm (and o-rings) did you order? You said stock. meaning the xxxx29 (STD) one? or the xxxx30 (AP) or the xxxx31 (AP 5NG1).

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Dude....thanks for that! I have been having a bit of difficulty with my big-bore equipped YZ250F. I will definitely check that out!

:banghead:

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Here's my old AP. And the other 0-ring is missing.

APfail.jpg

If the apump diaphram is that oxidized, you should also check:

- hot start plunger and cylinder

- slide vacuum plate and o-ring

They are probably in similar shape.

Upgrade the Apump return spring to merge racing too! ('04 and later). It makes a HUGE difference in throttle response.

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Thanks! Good to know before I pull the carb. Parts are ordered. I'll also be doing a 170 main jet and a YZ throttle stop thats missing.

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OK Yes, when i replaced the needle seat and o-rings and cleaned my carb, it made a huge difference. like 25-30% more power. like getting a new bike:thumbsup:

But the AP is bad, it idles high for 3-7 seconds after a rev comming to idle, but once it does idle , all is good. so again which AP diaphragm (and o-rings) did you order? You said stock. meaning the xxxx29 (STD) one? or the xxxx30 (AP) or the xxxx31 (AP 5NG1).

I ordered this one: xxxx29 (STD)

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Ok Parts arrived, rebuilt AP, moved to 170 Main from 168. Then tried YZ throttle stop--it doesn't fit? Still have 3000ish RPM hang on decel?? and 15-20% less power?

Took carb off again, (*@##!!) removed, cleaned and cleared out with air the main jet, pilot and starter jet. cleaned out hot start valve body, checked throttle slide, moved needle to position 4 from 3 AND did a makeshift taffy mod. Set fuel screw 2 turns out

After install and warmed up, reset idle.

Finally it's a rocket again! :banghead:

Idle is good, no high RPM hang !!

What fixed it?? Hard to tell, my guess is cleaning and new needle position.

This forum helped big time !

AP.jpg

CarbPart-1.jpg

Taffymod.jpg

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