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James2001400EX
06-30-2009, 06:47 AM
I have a 2001 400ex that I recently picked up. I brought it to a shop to have the valves tightened and they were also to clean the carb and replace the spark plugs. I cleaned the air filter and the thing starts great, but when i go to drive it there are issues. While hitting high rpm's through all of the gears the engine seems to bog down and lose power. Any thoughts as to what may be causing this? Should I rebuild the carb? Thanks,

James
rob_990
06-30-2009, 08:38 AM
sounds like its running rich.you might want to go smaller on the main jet.
flyboy1294
06-30-2009, 12:18 PM
Originally posted by James2001400EX
I have a 2001 400ex that I recently picked up. I brought it to a shop to have the valves tightened and they were also to clean the carb and replace the spark plugs. I cleaned the air filter and the thing starts great, but when i go to drive it there are issues. While hitting high rpm's through all of the gears the engine seems to bog down and lose power. Any thoughts as to what may be causing this? Should I rebuild the carb? Thanks,

James

I had the exact same problem with a 300ex when I first got it.

Turned out to be I had the choke on :grr:

I'd probably check the little stuff first, then I'd assume the jets. Good luck :macho
BEAVER.989
06-30-2009, 12:56 PM
Sounds like rich jetting as mentioned, but when you say high rpm, how high? These motors make their power lower and actually taper off high into the rpm range.
06-30-2009, 01:31 PM
Originally posted by BEAVER.989
Sounds like rich jetting as mentioned, but when you say high rpm, how high? These motors make their power lower and actually taper off high into the rpm range.

peak power is at about 7200RPM. at 9000RPM you are making the same power you would at 5900RPM. Mind you thats stock. Power doesnt really taper off like people think and revving them out before shifting will keep the shift drop closer to the peak power. I wonder why he would be rich though if they just cleaned the carb and replaced the plug.
powertechn2
06-30-2009, 11:00 PM
could also be lean on top. not enough fuel causes bogginess and loss of power too.

i would say carb issues. even if they "cleaned" it, it may still have gunk, sometimes just the bowl gets cleaned out and not the entire carb disassembled and cleaned. esp at places that say they are gonna change the spark plugs on a 400 ex :p