Pressure builds up in carb until accelerator pump won't push down

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Far from a carb expert (rebuilt lots of dirtbike carbs and boat carbs but not very many car carbs)...but if R is the acc pump, that passage you speak of looks to me like the passage that the gas should squirt out of when you pump the carb. If thats plugged up I think it would do exactly what your describing. No idea if its easy to clean out...Id soak it in some carb dip to soften things up then blow it out with compressed air if possible...trying to fish wires through tiny holes is always my last resort for carbs.
 
"N" is the acc. pump outlet. Youre gonna have to remove that G shaped retainer that holds the BB in the bottom of the acc. pump "well" (you can tell Im no carb guy),I used a hemostat to remove the retainer.Man that thing is small. DONT loose it, spray carb cleaner in there, I used stiff bristle brush to clean where the ball seats. You should be able to spray carb cleaner through that hole and it should come out the tiny acc. pump nozzel . Im gonna attach a pic. The red circle is the acc. pump outlet, The green circle is where I removed the little rubber O ring that would block the flow when the air horn was screwed down. sorry I wish I would have left the gasket off when I took the pic, its under the air horn gasket in pic.The blue arrow is where the acc. pump goes, that G clip and BB are at the bottom. I hope a real carb guy will chime in and educate us both.
carb pic.webp
 
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I'm confused. You can't push down on the accelerator pump piston at any time normally, since it is hooked up to the throttle linkage. If you remove the linkage, then you can push down on it manually and make it squirt. What am I missing?
 
I understand that . . .

But it wasn't until I had both the diagram AND "skidplates" red circles above for me to see that little port.

And going back 19 posts ago I asked you how/where to check and I didn't see a reply. Sorry.

The good news is, it's fixed and thank you for the help!
 
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dmaddox said:
FIXED!!!!!!!!! Thank you everyone for your patience - but the fix was indeed a plugged accelerator pump outlet!?!?! Sure enough I used a needled, cleaned it out, and it runs, idles, and has a snappy throttle response.

THANK YOU!!

-dallas

I hope this might help someone in the future :)
Click to expand...
Just experienced the exact same issue. I was dreading trying to think of the keywords to narrow this problem down on mud!
Cleaning the accelerator pump outlet with a bristle from a wire brush solved my problem also!!
 
Blast from the past - whew, 16 years ago. I recall removing that little BB down in the bottom of the accelerator pump passage (tiny clip and BB), cleaning it all out and reassembling. There was corrosion that had built up, restricting the flow of fuel. Good luck!
 
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It ended up being a clogged jet/port into the primary where the pick is in the photo. I did notice debris in the float bowl which you can see in the pic. Cleaned it all out and it worked flawlessly after putting it back together.

Still stumped about the debris. It’s got a new oem fuel filter, and I had another oem filter on before that for only about 1k miles…

IMG_8565.webp
IMG_8570.webp
 
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