yz450 problems with motor..

well i went to the race track today and sign up and go to fire the bike up and warm it up. It usually starts in the first 2 or 3 kicks. But today it started and i killed it when i gave it gas. then i did it again and it started and died then i thought i fouled my plug. i got tired of kicking and i went to go get the tools to change my plug. my buddie tried kicking and same thing it would run for like 2 seconds and shut right back off. kicked and kicked and kicked just kept runnign and shutting off. Finally one kick it kicked back real real hard. He went to kick it again and it wouldnt budge locked straight up. So after the races i bring it home tear the head off nothing wrong with the valves, take the sleeve off nothing wrong wiht sleeve or piston, look torwars the bottom in and nothing wrong. so i pushed down on the piston and it move a little i started pulling on the timing chain and it was freeing up. I went to push down on the kickstarted and nothing it just went up and down not doing nothing. so it seems that my kick starter gear is broken. I am going to take the right side case off tomorow and look and see what all happend. Has anyone had this problem with theres?


Never had that happen. Did the kickstart still turn the engine over after it backfired real hard? I doubt the gear itself is broken, could be something in the mechinism though. As for the bike acting up like that when starting, thats happened to me before. Did you leave the fuel turned on when trailering it? That is what usually causes my bike to give me a rough time starting. When it does that, I just take the plug out, and kick the thing over a bunch of times to clear it out, then heat the plug and stick it back in. That usually fixes it.

took the sidecase off second starter gear that connects to the flywheel was shattered in half. i will get a pic of it.

So that broke when the engine Kicked back? Ive seen a kickstarter snap flush off at the shaft from a kick back. It was on a 98 kx250.

Your bike is not getting gas or the correct gas/air mixture.

Instead of focusing at the carb, you have kicked, broken and finally torn apart your engine. :)

P.S: change the cam chain now that it is apart.

I had this very same thing happen to me.. it was the second day after i bought my brand new 04 yz450 and i took it out and kicked it and it started up then died tried kicking it again and it was locked tighter than a nuns &@#$. i was soooooo angry but i do recall it back kicking on me extremely hard the day i purchased it.. felt like it broke my ankle i was very upset but it turned out ok because that way i couldnt get too hard on it for the break in. anyways i loaded it up and brought it to the dealer where the kick starter gear had broken and that broke a chunk out of the case. almost 2 months later i got my bike back without a warranty and then it starts leaking oil by the shifter... i still havent gotten around to pin pointing exactly where it is leaking if its the seal on the shifter, cases, or that plastic piece.. but after a day of riding there is always oil down there.

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