2004 kx125 wont start i need help

[cdr]

the bike has a new top end with few hrs and i was going and it just cut out and died an wont start so i got new reeds,spark plug,and gas and the spark plug sparks an i cleaned the carb and still wont start i dont know what else to do any help with be thanked

[ascend75]

If it has compression, fuel and spark it pretty much has to start so you are missing at least one of those components. You say you have spark and if you thoroughly cleaned the carb then I would suggest doing a compression test. You can rent the gauge from oreilly's for free so it's a cheap avenue to investigate if you've hit a road block.

[Holguin #11]

Kinda the same scenario i had a while back on my sons KTM 105....ended up being kill switch grounded out.

[huffster]

You can unplug the kill switch on a KX. If your spark returns, then the kill switch is bad. Like Ascend said, Must have fuel, compression and spark to run. Make sure you have ALL THREE :)

[cdr]

i already checked the kill switch an its good someone told me its an exhaust seize? i have no clue wtf that is since its a two stroke

[Paw Paw]

Pull the exhaust pipe and look into the exhaust port of the engine.
Is the piston scored?
Does it have vertical scratches?
If yes to either...Then you have seized the ring to the piston and thus you don't have compression.
Did the piston that was put in have three very small holes at the exhaust port bridge? If not, then put them in
the new piston you will be installing. These little holes cool the exhaust bridge and help stop it from seizing.
Without them the engine will seize.

Paw Paw