Engine stalls and Kickstarter seizes - Please help!

I had this same problem on my last ride and I thought that I fixed it, but obviously didn't. I can kickstart the bike just fine and it fires right up and runs fine, but within a minute the bike will just stop as if it stalls. Sometimes I can kick it right back up, but it will die again and 1 out of 3 times the kickstarter will absolutely not move when I try to kick it and the wheel wont budge when I try to bump it. When I take a wrench to the flywheel and turn the piston it is pretty tight at first (almost a metal on metal grinding), but then loosens up back to normal and I can kickstart it again just fine, but the cycle starts all over. I'm racing it soon and am so fed up that I'm about to take it to a mechanic and dump a ton of change on this thing if I can't figure out the problem. This is on a 2003 YZ450. Please help!!!

Did you check your kickstart gear for damage? They have been known to be a weak point.

Sounds like you might be getting some piston/valve clearance problems. I had that same thing happen to me.......once. I've the engine in a thousdand pieces fixing the origin of the problem....a bad crank assembly.

Good luck.

I pulled the case off to check the kickstart mechanism and the torsion spring seemed like it was folded over on the kick axle. Instead of the wire coming outwards from the spindle it was at an angle and as the wire came outwards it looks like it was folded over and went upwards instead of being straight outwards. Could this be the cause of the bike stalling as well. I've heard that people replace the '03 kickstarters with the 04 mechanism...which parts would have to be replaced?

Sounds like the kickstarter problem is going to be secondary to the cylinder problem. If you've got metal on metal grinding sounds coming from your piston and a tightness at a certain point of the stroke you'd best pull that cylinder off before it gets REAL expensive.

Its in the kickstarter id bet money on it. I have seen them do this before. My buddy's wr400 did the same thing. Cant remember the fix exactly but it was in the kickstarter assy somewere.

I changed the torsion spring and shift shaft today with my other 2003 YZ450 and still no dice. I cant think of anything else that it may be...I guess the next stop is the mechanic (aka money drain).

You're not alone on the money drain. Sorry man. :naughty:

I have an obscure question?

Did you take the Carb apart and clean it?

In your story it sounds as though your not even able to ride the bike is that True?

One thing that comes to mind is if you did take your carb apart it sounds like you have the Slide plate on up side down

What you describe is exactly what happens if this is the issue

Just a thought

I was able to ride it fine all week last week in the same config and I can ride it for the 30 seconds to 1 minute that it actually runs. It seems like every time the revs drop on the engine the bike just quits.

Tear the bike down and make sure your valves are within spec. Turn engine over to check and see if you still hit that hard spot. If so I would take off the cylinder and investigate a little further. You might have more than one problem here. Either case it is not a good one. I would not try to start the bike more till you get it figured out.

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