400EX Won't Start

[d2kstang]

I have a 99 400EX, that is stock except muffler, K&N and changed the main jet. It has compression when you crank it, it has spark and it is getting fuel. Why will it not start. Am I missing something.

[racerdan24]

As stupid as this sounds....how does the plug look? when was the last time you started it or ran it?

[d2kstang]

Plug is light brown in color, it is about 6months old. I was riding in open field WOT and then all of a sudden it just shut off and would not restart.

[DirtMonkey]

Its also worth a shot to check and see if there is water in the fuel if its been sitting awhile.

[racerdan24]

What Dirt monkey said....seems like it has water in the fuel( You do have fuel in it correct???)...or a wire came loose some where. I would check every wire to make sure something did not break.

[hypersnyper6947]

Originally posted by d2kstang
Plug is light brown in color, it is about 6months old. I was riding in open field WOT and then all of a sudden it just shut off and would not restart.

Sounds electicle to me.

Will the motor turn over, oviously not starting, but at least go through the rotations?

Have you taken the plug out and put it in the boot and hit the start button to see if your getting spark?

[d2kstang]

Yes I did check to make sure I was getting good spark and everything was fine there. This is a fresh tank of fuel. It cranks just fine just with no start. I have not looked at all of my wires yet any specific ones to check.

[racerdan24]

I know it seems like alot of questions for ya....but....

Was this the first ride of the year?

I know this may sound dumb...but is the on/off sitch off by any chance?

Just thinking of the easiest things...I have done it with the on/off switch..hit it by accident riding.

[sprayedgt]

I know this sounds like a really stupid question buuuut... Is the gas turned on? I've seen it happen before a million times.

[d2kstang]

Yes to all the above

[sprayedgt]

Since you were at WOT when it shut off to me it sounds like a timing issue. Maybe the chain jumped and through the timing off. It the timing is off it will not start no matter what.

[Dathon Lawler]

a quick way to check to see if your timing jumped without tearing down your motor is open up your peek hole on the flywheel cover then rotate your flywheel to "T" then check to see if all your valves are loose by opening all of their access caps. by doing this you are making sure the cam is in the correct place. meaning all the lobes on the cam facing down. ifffff all the lobes are facing down THEN all your rockers should have a tiny up and down movement. sayin that is good. move on to the spark plug. i am thinking this as i go. soooo... take out the plug and make sure the piston is on top dead center. BUT!!!! the cam rotates half the speed of the crank. so. if it doesn't match up first, don't call it quits. turn it again to the next "T". and re-check. with all that being said.
you are ultimately looking for the relation of "T" and looseness in the rocker arms. if you can't get them to match up then you have more than likely jumped a tooth. then you will need to tear it down obviously and also get a new cam chain tensioner and check to see if any of your rocker top bolts are loose or stripped out. good luck. i really do try and help people on here. hope this helped narrow it down.

[Sanddraging28]

my 2 cents would be something electrical. did you check the plug on the CDI?? how about the connectors under the front plastics?? it might be a long shot but maybe the coil or the pickup in the left case cover??? did the spark plug wire come loose from either the plug or the coil.

did the head gasket blow?????

is there junk in the carb???

[d2kstang]

Thanks guys that will give me some more things to check. Is jumping timing something that happens often. And would there be any other signs of a blown head gasket not like a car since you don't have coolant. Thanks again.

[jelrod05]

check the cdi box i had my go out and it wouldnt start.

[rob_990]

Originally posted by d2kstang
Thanks guys that will give me some more things to check. Is jumping timing something that happens often. And would there be any other signs of a blown head gasket not like a car since you don't have coolant. Thanks again.

look for oil coming out the side.

[d2kstang]

If the CDI went I would not have any spark would I. Also if I did get it to hot whats the possibilty that I hurt the rings but it does still try to build compression.

[d2kstang]

Could I have glazed rings not allowing it to build enough compression to start.

[Sanddraging28]

Even with glazed rings it should start...i have seen so that wouldn't start though. i am still thinking its a head gasket......

and with a bad CDI you may still see some spark at the plug, either not strong enough or at the wrong time