03 400ex wont start.... weird!!!

[400exrider36]

so i found an 03 400ex a couple months ago for 3000 bucks in great condition. the guy said he just needed to get it running since one day it just wouldnt start. he brought it to a professional and after weeks and weeks of trying everything he couldnt figure out what it is. Finally the guy said he was so fed up he'd sell it to me for only 600 bucks!!!!

Symptoms::

It just turns over and has a slight repetitive fire every few turns of the engine. only a quick slight "putt" tho

Carburetor was cleaned and checked over 3 times, and replaced with a different one....and still didnt work

Brand new cam and the timing is correct...

Has spark....

fuse is good....

after turning it over a few times the plug is soaked in gas.... either way, i would think it would at least start for a second it if was too rich...

it baffles me that it ran so good then all of a sudden quits and does this.

What is causing this?
Please help!!!!

:ermm:

[slightlybent47]

Sounds like your just going to have to go over everything, but I would check all the wiring and all connections. Try turning the fuel off and just squirting a small amount of fuel in the carb and see if it fires up. Maybe it's getting too much fuel. Could be the coil is working but not putting out enough power to get a good strong spark.

Good luck

[400exrider36]

i was thinking possible the coil too....
my buddy has a 400ex too and i was gunna borrow it and swap everything to see what happens....

he had a problem with his coil where it wouldnt start but it still ran 50 percent of the time.

[400exrider36]

well i checked the timing and that was right and made sure all the wiring had good connections. it then fired right up!! ran great until about 10 minutes later it just quit... i turned it over and over and i would almost start then quit everytime. finally it just started right up ran great till it did it again 10 minutes later. havent gotten it to start back up but....
im still thinking its the coil

[slightlybent47]

Sounds like the coil is getting hot and losing power. Check the ground and see if it has any corrosion on it. But I would check the battery as well and all the wires again just to make sure. Mine would cut out from time to time and it was a lose conection on a small wier by the battery.

[beags86]

i would say coil.

my 250r did the excact same time. some coils will heat soak and quit working. i pulled my hair out for three months trying to figure out what was wrong with my r. finally got a new coil and it was good to go after that.

sometimes it hard to believe that some "pros" can't figure this stuff out. and how they even get jobs as so-called mechanics.

[400exrider36]

well..... i swapped the coil with a new one along with the electric box in front and metal finned thing in back (forgot what they are called...) same thing.

took the carb off and it squirts gas across the room.... enough to start it.... and seems to be fine

only other thing that it could possibly be is a loose connection i would think. i havent checked every connection or even the ground and battery terminals.

HOWEVER, my friends 400ex turns over much much faster than mine.... even with the battery charger on mine... so it makes sense if theres a bad ground or connection... i hope... ill work on it tomorrow and let everyone know.


Thanks for all the suggestions :cool:

[400exrider36]

wwaaaiiiit.... what about the stator and all that?

[brokenmike]

my quad had a problem where it would not start and it had spark. It wound up being the stator. I changed the stator out and fired right up...

[400exrider36]

Well that sounds promising..... Maybe I'll try that... I ohm tested it with my friends and the numbers are close to the same. But I don't know if that means much

[aDviSol2y]

You should be running 5k ohms. Check your spark plug wire. disconnect it from the coil, and the plug. Put your ohm tester to it. If you read 5k ohms you should be good.

[400exrider36]

When I tested mine it gave me 3200 on one pair and other was an unstable reading almost like a capacitor would give you... My buddy's did the same but with 2700 ohms. Idn what that means but I was thinkin maybe the pickup is bad at least

[4reeds]

Did you ride it when it started? If so, how did it run?

[sc400ex_rider]

sound like a pick up. they are called hall effect sensors and can drop out when they get hot. good score for $600

[400exrider36]

Ok I'll try that. It runs awesome when it runs...
I'm gunna order a Ricky stator 200 watt now so if that's not the problem I at least get an upgrade out of it lol

[400exrider36]

another question....
theres a nice blue spark that fires every cycle.... to me that seems like that would indicate it is ok..
is there any way it could still be bad.... im gettin frustrated

[sc400ex_rider]

not really a fat blue spark is good. even if it was intermittent it would start but break up. still thinking it might be your ign. pickup by the stator.

[400exrider36]

Ok thanks for the response I'm just gettin nervous that's not it... But I guess I gotta expect that with this kinda stuff

[honda400ex2003]

you should check the pilot and f/a screw to verify that they are indeed a 38 pilot and 2.25 turns out on the f/a screw while it is apart. it sounds like your switch may have a loose wire or something. I would check out your killswitch on the bars inside too. they are known to get bad if left outside or get muddy then powerwashed. Other than that, it has spark, it is getting gas, has air. it is all there. i would check the quick disconnects too in the front to make sure they are making good contact along with the switch in the front. you can check for continuity through the switch when it is in the on position i believe. I think it is a normally closed switch so it should be connected when in use. when in the cut position it should not have continuity i dont think since it would be open and the connection would be lost. although, if it is normally open it will be the opposite. I am about 90% sure it is normally closed though since it is not grounded out making it closed normally. just another idea to check out. steve

[400exrider36]

The killswitch button is broken off and the key ignition has been cut off and reattached... Not sure what in checking for but I'll mess with them.

[honda400ex2003]

that would be where i start looking :eek2: steve

[400exrider36]

Everything is good.. the killswitch is completly taken out and the key is fine. Hmm

[400exrider36]

:mad: :mad: :mad: :mad:
the new stator and pickup didnt work...
only thing left that could be wrong is the cam chain, tensioner, and valves i believe.

but heres what i have found.....


if i manually turn the engine forward there is barely any compression.
if i turn it backwards, i can barely do it from the compression.... or maybe its just bad to do that.

it seems like the timing is way off to me.... but doesnt make any sense why it started, quit, then started again...
so im thinking tensioner? the chain seems tight but idk

[400exrider36]

it has a brand new cam in it.... but what about the decompressioner? probably not since it did the same thing on the old cam

[400exrider36]

ok well i finally figured it out i think....


the mechanic who worked on it said the valves were all good and things were adjusted right.....
i went to check the valve clearances anyways.....

well they were so tight all 4 wouldnt close all the way. i adjusted them right and it fired right up. it would ping and sputter every few seconds which sounded really bad but it went away after about 30 seconds.

anyway i went for a few minute ride and when i got back the valves were ticking loud which means i gotta adjust them again...
is that normal to have to adjust them that soon?

[4reeds]

Not after a min. ride. Did you adjust at tdc? What cam did you put in it?

[400exrider36]

yeah and its a brand new stock cam.... they may not need much if any adjustment too, i still gotta check.
im just not used to the 400ex tick.
ill post back how the clearances are in a bit

then maybe this thread can move out of here since im sure everyone is sick of it by now ;)

[400exrider36]

Ok so two of the valves were .003 off so I adjusted them and the tick went away.
Rode it for about an hour and now it ticks extremely loud when I floor it. It fine if I just take it easy tho... :ermm:

[honda400ex2003]

this time make sure you tighten them down tight and give the adjustment another try. It that does it for a little while again and it starts doing it, i would take the cover off and inspect all tolerances since something is probably pretty worn. just my .02 though, steve

[400exrider36]

this sounds wayyy to loud to be a valve tick.... and why would it only do it under load?

[honda400ex2003]

check your cam chain tensioner too to make sure that is working properly. make sure it is fully in before you install it again. steve

[4reeds]

sounds like the cam chain guide is worn.I had to do mine about a month ago. check out 400ex noise on youtube. see if its comparable.Mine sounded the same and sure enough I changed it along with the chain and it went away.

[400exrider36]

Wow two of the head bolts were just about off and was leaking through the head gasket....

[400exrider36]

Wow two of the head bolts were just about off and was leaking through the head gasket....