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Joe Krystofek

Honda400EX Honda 400 Ex Running well but bogging out on steep hills

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I recently bought a 2003 Honda 400 EX. Ive had the bike for a few months now and went riding about 8 times so far. When I first bought it, it ran poorly. I Changed the plug, cleaned the K&N air filter very well. Went riding It preformed much better but I noticed it would bog out in 3rd 4th and 5th at higher rpms. about mid rpms for those gears, So last week I pulled the carb all apart and cleaned it very well. I also found that my air fuel screw was way off so I set it at 2 1/2 turns out, the bike seemed to run almost with twice as much power as when I first purchased it! I finally felt happy until last nights ride, I tried a big hill climb and bout 100ft up the hill the bike bogged down very bad almost like it was choking out or running out of gas. I down shifted to 1st and she still wouldnt make it to the top. I actually had to just coast all the way down backwards which sucked haha. The only thing I could think of is that I need to rejet the carb, it has a HMF Silencer ( The header looks stock to me ).  Im just racking my brain over this bike, Im new to the site and if anyone can help me I would really appreciate it! 

Edited by Joe Krystofek
miss spell

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Posted (edited)

First, get rid of that K&N filter and re-install a proper oiled foam element.

There are no noticeable performance gains from it and, they allow fine dust thru your engine.


If the engine otherwise runs fine on flat ground, it is not jetting related.

By your description it sound like a float / fuel level problem.

Edited by mlatour

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