400ex bogging issue (dont think its carb related)

[japawhat02]

So ive had several of these quads and have never experienced this. The bike starts idles and revs fine. If i put any load on it, say regular riding it bogs. Pulled the plug and it is black, super rich. Valves in spec compression within range. I have a full pipe with uni filter and drilled air box cover i am running 160 main 42 pilot. Bike was running fine Saturday, and started showing this symptom on Tuesday. I pulled the carb dropped to a 155 and put in new plug. Same results. can rev all the way up to the limiter w/o hesitation in neutral and in gear while not moving, but as soon as i start to go it bogs. It almost seems like its not advancing the timing. Any ideas. I ordered another cdi to have a spare, but it wont be here for a few days. TIA

Jeremy

[ride red 14]

What happens when you try to ride it without the airbox lid? Also check and make sure the choke isn't trying to close. Sometimes the 400ex choke will get weak and not want to stay open.

[DragonGunner]

What happens when you try to ride it without the airbox lid? Also check and make sure the choke isn't trying to close. Sometimes the 400ex choke will get weak and not want to stay open.

I was thinking stuck open choke also.

[japawhat02]

Ill give those a shot tomorrow, i dont think the lid being off will efffect anything as it is pretty free flowing as is.

[japawhat02]

negative on both, taking it to a friends house to swap cdi boxes.

[Kjs116]

If you are still having the issue with 400 bogging, check to make sure the accelerator pump is in fact shooting fuel into the intake side of the carb.

[slightlybent47]

I run a 450 carb on mine. And after the last build, it started automatically closing the choke when at full throttle.
I had to lock it in place.
It never did that before.
Check the fuel inlet tube on the carb. There is a fuel screen inside that tube. Check it.