Why does my 2004 kx250f not start?

Likely valves. Service manual is a must for all, for sure take a few bucks to invest in one.

When the mechanic was looking at your bike, do you have more details to share other then some one said the bike had low compression?

The mechanic also told me to buy a new cylinder and piston but idk if I should do that before checking the valves bike also has some holes in magneto and is overheating and coolent is coming out of the overflow.

Richard Aira wrote:

The mechanic also told me to buy a new cylinder and piston but idk if I should do that before checking the valves bike also has some holes in magneto and is overheating and coolent is coming out of the overflow.

Sounds like a blown head gasket?

my best friend has a 04 , valve probs since he got it .. i raced it once in 06 on its third motor ... dropped a valve on a 100 footer ... i was laid up for months ... needless to say ... if it starts by push starting it turn to the valves first ... the 04 and 05 has soft valve seats and is probably the most un reliable motocross bike ever made ... they were just problem riddled bikes man ...


sorry!

Sounds like you should sell it and get a better bike. By the time you get a cylinder and piston kit youre at $500. Nevermind the other stuff.

Low compression can be leaky valves, leaky gaskets, or a worn piston, even a gouge in the cylinder.

Leaky valves mean you need the head reworked - new valve seats, valve guides, seals, valves themsevles. Thats big money. At least $400.

Mind you these prices are without paying someone to do it for you.

That was the most unreliable 250F ever. Most of them around here clanked to a stop often.