400ex wont start when its cold

[TCracin440ex]

my buddy has a 400ex 02 and it will not start after its been sittin for a few hours or so....he can roll start it and it will fire up just fine and the battery aint dead cuz the starter will turn the motor over just fine...it will just turn over and turn over.....but if he roll starts it then rides it for a while he can cut it off and a few mins later start it right back up with the e-start...somebody tell me whats the problem because its stumped me...

Dose his nutral light still work?

Try wiggiling the wire that is down near your gear shifter.

[400eXr1d3rZ]

Does it have a 42 pilot?

[TCracin440ex]

all electronics sill work, no 42 pilot jet....just a dynojet kit

[400eXr1d3rZ]

Something could be blocking the fuel from getting to the carb, take a look inside of the tank. Just throwing ideas at you, but take apart the carb and see if theres any junk in it.

[CDCHONDAS]

make absolutely sure but there are one way clutches for the starter to drive the engine, when the oil is cold and they are getting shot they don't work so well, the engine will still spin just not fast enough, its really hard to tell sometimes. however have someone who knows check it unless you like spending money

[atvRiDa400ex]

usually when its cold and u have an aftermarket exhaust of any kind its going to take some jetting to get it started.

[cals400ex]

does he have an aftermarket rev box? if so, that is likely the problem. if not, then put in a 42 pilot jet. start around 2-2.5 turns out from lightly seated on the fuel screw. when starting the bike go and turn the key on. then pump the throttle 5 or 6 times. then hit the start button without hitting the gas anymore yet. if it doesn't start then try pumping the throttle a few more times. you don't want to keep nailing the gas though because the accelerator pump in these carbs will flood it out.

[cals400ex]

also, put a new plug in his bike. they do go bad from time to time. NGK dpr8z is the stock plug.

[vanhornracing]

when your buddy tries starting it when it is cold try choking it a little. if that doesn't work try pumping the gas some.

[johnsls]

None of this makes sense to me. (maybe I'm missing something)

He can't start it with the start button.. BUT he could roll start it.

I can't see how this has ANYTHING to do with his jetting. If his jetting was off it wouldn't roll start either... RIGHT?
:confused:

[vanhornracing]

try choking it or pumping it......

[TCracin440ex]

this is my old bike...i know i was an idiot for selling it 2 my friend...but i had it for 5 years....i jetted it myself....everything on the bike is fine...it started fine for 5 years with an aftermarket pipe....right now it has a TC shorty on it, k&n air filter, and a magnum rev box....it ran like a top when i sold it...and just recently it started doing this..

[DieselBoy]

Before you lose sleep over it, put a fresh plug in.... if that doesnt work than examine the carburetor. Use the accelerator pump to give it a healthy squirt so it can fire.

Check the spark plug. if after turning it over you see that its wet than it could be flooding, or if its not then the fuel just aint making it in.

it is that magnum rev box...

those are from a dirt bike...not designed for a e-start 400ex. there is a circuit in it that will prevent the spark from firing if it does not reach a certain rpm. this is to prevent kickback of the kickstart lever.

the rpm that the bike starts at is just above that cutoff. lets say that the 400ex starts at 2000 rpm(just a number, i am not sure what the starting rpm actually is), and the lowest rpm that junk rev box will allow spark is 1950. they are very close together, so if everything is perfect with the bike, it will reach the starting rpm. now addin thicker oil due to colder temps, a slightly drained battery, cold temps affecting the jetting and that starting rpm is now a lot harder to reach, as is the minimum rpm for spark.

i put the stock rev box in and it fired right up...

i learned this after i killed a battery and then a brand new battery i had just bought for my other bike. it was an expensive lesson learned, but the 400ex still has the stock rev box in it...

[cals400ex]

yes, i don't have any experience with the magnum but the only one that started good in winter that i have used is the gt thunder one. well, the stock one too....

[MadMan400ex]

i know you said that the battery was good, but i would replace it if it's less than a few years old. i had this same problem. crank, crank, crank. but few sparks. and i could have my buddy pull me and i'd drop the clutch and off i'd go. no problems the rest of the day. i ended up taking it to the shop and while the battery had enough power to crank it over, it wasn't enough to light the fire. something about a dead cell (???) not holding a charge over time. new battery and problem was fixed.