A couple of assumptions:
1. The bike ran fine before the piston was replaced (well..relatively)?
.oh...that's only one assumption.
While it may well be something else, it's a good bet it's something related to what you did or didn't do...agreed? (a 'something else' would be the six months the bike sat while the 'rebuild' was happening. 'eh??)
Ensure your fuel is fresh. Ensure you are getting fuel too the carb bowl. It doesn't take a real long time to get a sticky float.
Is the plug wet? I presume 'no gas on plug' means it's not? Replace it on GP. If it's dry...you either have no fuel or the reeds are stuck.
Did you note that the reed block fits in only ONE way? You CAN put it in upside down just as easily as right side up. Take off the carb...look into the intake boot. The boot should transistion smoothly to the reed cage. If you're looking at a flat piece of the phenolic (the white stuff), it's upside down.
While your looking at that...make sure the reeds are NOT stuck. Stick your pinky in there and move'em around. Well..OK...not 'around'...up and DOWN...howzzat?
While you're at it...just take the reed assy out and make sure the piston isn't backwards. You should see a couple of holes in the piston skirt on the intake side. If you don't see any holes, it's backwards. Oh my...I've not SEEN a Wiseco for a KDX...they DO have holes on the intake side...right?
Did you have the carb apart? Is the nylon cable retainer seated properly (tab of nylon IN the retainer nut slot)?
Does your choke work? Does it 'stick' up when you pull on it?
If your plug is dry..there is an ingestion problem. No fuel.
Carb
Reeds
Backwards piston
You're familiar with this sort of thing?
Wouldn't it be a hoot if you forgot to put in the wrist pin!!! :laugh:
...ok...that wasn't very funny.
You DO have compression? Take out the plug, have someone kick the thing while you try to plug the sparky hole with your finner. You should NOT be able to do that...the bike should blow your finger off the hole.
Post the resolution!! We all wanna know!!!