Need HELP A.S.A.P.!!!!!!!!!

[KY_YFZ_04]

I just put in a new piston and rings in my 400ex. What had happened was i dropped a valve out of the head and got stuck in the piston. Anyway........ I had the head worked with new valves and everything. The valves are adjusted to spec. , the carb. is suckin' air, and the plug is getting fire. The cam is also i time but it just won't start. Anyone have any suggestions????

[key4202003]

did you drop the plug? they break easy. also if its port and polished maybe not big enuff main or piolt also make sure timing is on

[prepracing]

is it cranking but will not fire ? is spark plug wet ( getting gas ). Did u check fuses, ground wires, kill ( on-off switches ) ?

[400exrider0004]

make sure to check plug, fuses, in nuetral, and make sure gas is on. I always have the same problem( won't start) but i always forget to turn the gas back on

[KY_YFZ_04]

gas is on.............. carb. is spraying fuel.......... i checked the plug for spark by holding it to the engine and cranking to see of i see spark and there is some. It is timed correctly i've checked that about 5 times already..........fuses are not blown and its in neutral.

Spark plug is also getting fuel you can take the plug out and smell fuel on it.

[key4202003]

port and polish? too rich is my guess what mods, plug, did it ever run after rebuild, what is the carb at main piolet, a/f screw?

[KY_YFZ_04]

guess i used the wrong words when i said the head was worked.......... it is not worked............just repaired with the new valves nothing else.......... i haven't changed the jetting in the carb. since the head dropped the valve so i assumed i shouldn't have to do that to get it to start ........... only mods are a cam hot cams stg. 1 and that was done before the head dropped the valve.

[the Z Man]

could it be 180 degrees off on the timing?

[prepracing]

you did say new rings right ? I did remember a EX where his new rings stuck ( don't know how but they did ) and the gas just went right on by and down into the motor instead of combusting = 4wheeler starting

[KY_YFZ_04]

yes it has new rings, and i honed the cylinder before putting them in getting the nice cross hatched look that you are suppoed to get before applying new rings

[TCracin440ex]

well you got all the right combinations for a running quad...cept 1 thing...did you stagger the rings when you put them on the piston....thats the only other thing i think it could possibly be

[key4202003]

get a BFH and beat the deamons outta it, yeah i agree check compression, or air leek in head gasket, if all else fails buy new quad (very good excuse to buy new 450r, HELLA!!)

[the Z Man]

Originally posted by the Z Man
could it be 180 degrees off on the timing?

[KY_YFZ_04]

Originally posted by TCracin440ex
well you got all the right combinations for a running quad...cept 1 thing...did you stagger the rings when you put them on the piston....thats the only other thing i think it could possibly be

rings were staggered


Originally posted by key4202003
if all else fails buy new quad

already bought a new quad YFZ 450 :D , I had to get something fast you know :cool:

[TCracin440ex]

uh...well damn dude then it cant be nothin but your timming

[KY_YFZ_04]

Originally posted by TCracin440ex
uh...well damn dude then it cant be nothin but your timming

its not the timing..........here's how i checked it

brought up the cylinder like i was going to adjust the valves makin' sure it was at Top Dead Center and had movement in all 4 of the valves. the i loosened up the cam cover/valve cover and looked at the cam the lobes on the cam were down and of course the timing marks on the cam gear were lined up parallel with the top of the head and the other one pointing in the upward direction.

[TCracin440ex]

idk what it could be then...if the motor is turning over and everything...your getting fuel...your getting air...sounds like to me might be getting a weak spark

[KY_YFZ_04]

Originally posted by TCracin440ex
idk what it could be then...if the motor is turning over and everything...your getting fuel...your getting air...sounds like to me might be getting a weak spark

if it happens to be a weak spark what can i do to fix that problem? or at least check it???

[TCracin440ex]

most likely weak spark comes from old plug or bad coil

try to replace your plug first...if not its the coil...if its not the coil then its the stator or magneto...most likely its the plug or something minor...

check your flux capacitor too


lmao j/k

oh yea...might be a no brainer but see if your kill switch is in the on position it should be right in the middle

[KY_YFZ_04]

Originally posted by TCracin440ex
most likely weak spark comes from old plug or bad coil

try to replace your plug first...if not its the coil...if its not the coil then its the stator or magneto...most likely its the plug or something minor...

check your flux capacitor too


lmao j/k

oh yea...might be a no brainer but see if your kill switch is in the on position it should be right in the middle

i'll check that as soon as i get out of bed workin' 3rd shift is a killer on the sleepin habit........... and i've replaced the plugs already 3 times, coil will be next, then on down the line .........thanks man

[TCracin440ex]

i mean i might make myself sound dumb here but ive had that switch be off and ive turned the bike over and over again and it wont start...im wonderin why it aint firing...and im pullin the sum bytch apart and ill look up and see the switch is off and im like well damn what a dumb ***

[KY_YFZ_04]

Originally posted by TCracin440ex
i mean i might make myself sound dumb here but ive had that switch be off and ive turned the bike over and over again and it wont start...im wonderin why it aint firing...and im pullin the sum bytch apart and ill look up and see the switch is off and im like well damn what a dumb ***

i've checked that swith a dozen times cause i've done that before in the past myself, makes you feel like an idiot.

[TCracin440ex]

then its your coil...im willing to wager its some connection loose some where...its got to be wiring but it confuses me because your getting spark...im going to put my money on bad coil wire or bad wiring connection some where

[KY_YFZ_04]

Originally posted by TCracin440ex
then its your coil...im willing to wager its some connection loose some where...its got to be wiring but it confuses me because your getting spark...im going to put my money on bad coil wire or bad wiring connection some where

i'll check the coil..........but i didn't know that it would throw out a weak spark just thought it woud go bad eithe work or not work. but i'll check it for sure

[duke416ex]

When you put it tdc, did you just do it by letting the valves move and then getting play, or did you actually line the mark up on the crank? If you didn't do it by lining up with the t, it could be 180 off. Are the valves set to the right clearance?

[F-16Guy]

Originally posted by the Z Man
could it be 180 degrees off on the timing?
It doesn't matter on this engine.

[khen]

What CDI box are you running? Is it stock or an aftermarket? If it's an aftermarket make sure your battery has a good charge and/or try swapping it out with a stock CDI.

[duke416ex]

Originally posted by F-16Guy
It doesn't matter on this engine.


May think i am dumb, but why does it not matter? If the cam is 180 off then when the crank comes around it will fire at the wrong time. If it tis firing when there is no air/fuel in the cylinnder the motor will not run. I mean, I may be wrong, but does the motor not fire off a certain spot on the crank?

[KY_YFZ_04]

when i timed it i alligned the T and slash up with the mark on casing as you are supposed to............. and yes this motor can be 180 out if the cam was installed upside down with the lobes up and the piston at TDC.

[KY_YFZ_04]

Originally posted by khen
What CDI box are you running? Is it stock or an aftermarket? If it's an aftermarket make sure your battery has a good charge and/or try swapping it out with a stock CDI.

I am running stock CDI, battery is at good charge i've charged it up to makre sure i was getting addiquate spark which i guess i'm not

[KY_YFZ_04]

I found out the problem. I done a compression check and I only got 38lbs - 40 on the gauge...........guess i must have bent a rod and its not allowing the piston to come all the way up to TDC. Funny thing is though when the old piston was in it, the one when the head messed up i could bring it up to TDC with the head off so i thought that the rod was fine. Guess I was wrong.

[RiderTRX400ex]

euggh... that sucks

[DiRTdiGGr660]

before you tear into the engine to replace the rod...double check the valve clearance..you could have a valve to tight causing it to not hold compression..which would sho 38lbs of compression. and also, i dont kno much about that exact motor, but does it have a compression release somehwere in the cam or the head??i would check those things first before i split the cases

BTW..when you had the head off, and u brought it to TDC did the piston come ALL THE WAY to the top, top of the piston is absolutly even with the top of the cylinder, if it was then your rod is not bent

[KY_YFZ_04]

Originally posted by DiRTdiGGr660
before you tear into the engine to replace the rod...double check the valve clearance..you could have a valve to tight causing it to not hold compression..which would sho 38lbs of compression. and also, i dont kno much about that exact motor, but does it have a compression release somehwere in the cam or the head??i would check those things first before i split the cases

BTW..when you had the head off, and u brought it to TDC did the piston come ALL THE WAY to the top, top of the piston is absolutly even with the top of the cylinder, if it was then your rod is not bent

There is a decompression thing on the cams but that is on the stock one the hot cam doesn't have one.

And yes the piston did come up to TDC even the old one did cause i checked to see if it would come even with the top of the cylinder before i took it off. What may have happened was the person didn't put the valves back right or something, and i'll double check my clearance on my valves to see if that might be the issue.