could this be it?

[red400ryder]

could using a used cylinder head gasket that was already on the motor cause the bike not to start when its put back together after a tore down. even if the bike seems to have compression and spark and getting gas and timing is right..I've checked it all and they all work..so could using the old gasket cause it to not start up cause its not sealed fully? somebody help me out here understand this thanks madmike

[416mx]

Always use new gaskets, could be loseing compression, if it not about aleast 100 psi it won't start.:confused:

[red400ryder]

thanks 416mx i got new gaskets in today so i will try it and hope for the best thanks again madmike

[red400ryder]

well still no luck..got new gaskets on and still my bike won't start it just turns over and makes a noise like it wants to start but won't..everything is right i know unless i'm reading the timing on it wrong but me and a friend verified it was spot on so if anybody has any suggestions please tell me cause i'm goin crazy over this thanks madmike

[cals400ex]

i would bet its not the old gasket. i have seen them re-used before. i would check to make sure you have gas in it and make sure your fuel is on and the run switch is on. also, maybe you just fouled a plug. if you don't have compression, your problem may be elsewhere. i assume you have the plug cap on the plug too. you could also have another bike to try and pull you around to see if you can pop the clutch to get her fired up.

[mustang93]

could the timing be 180 degrees out?

[red400ryder]

well i think i have found the problem...for one i had no compression cause one valve isn't seated on the exhaust side and we tapped on it lighty and turned over the motor by hand and could feel the difference in compression..i think i am goin to take my head to a machine shop and get the whole head tuned up and fixed cause that is where the problem is coming from but anyway thanks everybody that helped later madmike

[PHIL_B54]

Originally posted by mustang93
could the timing be 180 degrees out?

if i remember right the 400ex sparks every 180 deg

[red400ryder]

regarding what was last said about it firing every 180 degrees...well i was curious about the tdc mark and the cam lobes down..does it matter which way you do it cause at tdc and cam lobes down you can turn it all the way to tdc again and the lobes are up then and turn again and back down so my question is then that either way it will run right cause if not then which 180 degree are you suppose to put it on to time it properly..just curious about this cause i just checked it out and am wondering thanks for any feedback madmike

[PHIL_B54]

yes you are right, the cam lobes dont have to be down, they could also be straight up. but with the lobes down the rockers will not touch the cam. basically that way you do not have to fight the valve spring tension when you put the cover back on the top.

[300EXbeast]

now this may be wrong but my buddie gots a 250x and we went ridin the other day and his died so we checked spark and gas and everything we tore it down to nuthin and cleaned everything in the motor and out redone timing and we unplugged the little box on the frame (i forgot what it was called but the metal one with the fins?) and she fired right up