02 400ex help

[KX250frider]

I bought this 400 not running, re-timed it and rebuilt the carb. It now will start but will not stay running unless you keep it at half throtle. Any thoughts on this? Battery is shot could this be causing the problem. I have just been starting it by putting a charger on it, but it kicks off as soon as the engine fires. Any suggestions?

[honda400ex2003]

id def get a battery and see if that fixes it. if not, at least you can check it off the list.

fresh gas?
What was originally wrong with it to make you do these things?
compression psi?
air filter cleaned out?

pilot could still be clogged up on the carb causing it to run rough but there are a few other things to answer here.

steve

[KX250frider]

It had recently had a new piston and rings put in it and it was a couple teeth off time. Just decided to go through the carb while i had it off. Gas is good airfilter is clean.

[honda400ex2003]

what size piston is in it? did it run well then start running bad or has this been since the rebuild?

what is your current jetting?

i would think something with the jetting but i cant be sure yet without knowing those too now that we know what else was done recently.

steve

[KX250frider]

From what the guy told me that i bought it from it has been running like this since the rebuild. not exactly sure what size the jets were but now that you mention it that could be the problem. It does have an fmf titanium 4 pipe on it.

[honda400ex2003]

check out what the main is, the needle is at, the f/a screw is at turn out wise, and the pilot is.

do you know what piston is in it?

a 42 pilot would probably be a good investment at around 2.5 turns out to help out starting.

im willing to bet that it has a 38 in it now and is running pretty lean on starts making it deprived and wanting to kill.

just a prelim thought though.

steve

[KX250frider]

okay finaly had time to get the carb back apart and it has a 50pilot jet in it. After looking at the plug tho its pretty clear i am not getting fuel.

[CJM]

Clean the carb, perhaps the float is stuck or the jets are dirty.

[KX250frider]

I have already done this and every thing looked good. Just not getting enough fuel.

[CJM]

The only things causing it to not get enough fuel is the carb or the flow from the tank.

Trust me, you may think its clean in the carb-but it might not be. I had the same exact issue with a YZF about 2 months ago. Took it apart and the needle for the float was getting stuck. Your jets, needle, float needle or float could be bad/clogged up. Cause a 50 pilot is more than enough, unless your main is way to small-but even then it would run.

[tri5ron]

also commonly overlooked, due to it is rarely a problem,....
BUT, it IS a possibility.

Bikes that have been sitting for extended periods of time can have fuel gummed up in the petcock, fuel line, or filter screen or can have dirt, grime, junk clogging it.

many people do not realize that there is a very fine screen in the fuel petcock.

Check the flow coming out of the petcock.
Pull the fuel line off of the carb, and turn the petcock valve on.

Check it on both the run and reserve settings.
(I'm assuming there is plenty of FRESH FUEL in the tank).

There is also the possibility of water in the tank from condensation, from sitting.

also check the gas cap vent line for any clogging.