My son washed my air box on my 07 kx 450. I took the plug out and rolled the motor over to make sure there was no water in the cylinder (a little water blowed out). I put everthing back togather and tryed to start it, it tryed to crank and died. when i try to kick it over now it is very hard. does anyone know what mite of happen

SOURCE: 2006 KX 450. New season

replacing plug maybe an issue get back to me buddy

SOURCE: I recently rebuilt the topend on my son's 01 kx

I'd bet you 10 to 1 it's not the coil. It sounds like it is starving for fuel and needs a carburetor adjustment. When you rebuilt the top end, did you put a bigger jug and piston? If so, your problem most definitely is the carburetor needs to be re-jetted.

What caused you to rebuild it? Did it seize, or quit running? Was it losing power before the rebuild?

That's where my money is but if you still believe it is the coil, you can check it with a spark checker. This is a handy little tool you can find at AutoZone, Harbor Freight, etc. It's a one piece tool that connects between the plug and the coil. The plug stays in but you remove the wire and put the checker on, one side connects to the plug, the other side you connect the plug wire. There is a light in the middle that will flicker when you crank the engine if it has a good coil.

Put the checker on and start the bike and see if you are losing spark...if the light stops flickering at top end, then you do have a coil issue...but like I said before, having seen this problem hundreds of times, my money will be on re-jetting the carburetor.

SOURCE: wont start by kick start but will by pull start

it could be the gaskets around your carb are bad and leaking air if so its thinning your gas fumes with more air then what is needed inside your combustion chamber witch is causing your engine to stop running like that. best of luck