Can you tell me the problem??

[YZ400EX]

Here is what happened on a 350X motor while rippin up some dunes!! The intake valve snapped off, hit the piston, rattled around for a second or 2 and stuck in the head. It broke the end of the pug off and grinded it up a bit, smashed a good chunk out of the piston, but amazingly didnt even scratch the cyclinder..Anyone know where I can buy a cheap 350X head??

[YZ400EX]

The sand is all over the motor from being pulled back out of the dunes after the engine locked completely up!! Here are some pics of the head..

[YZ400EX]

I have never seen a valve snap off and stick in the head like this before..

[YZ400EX]

I really dont have any plans of repairing this motor if I cant find a cheap head so if anyone is interested in an almost complete 350X engine let me know..The botom end and cylinder is still perfect..would just need a head and piston..

[spent21]

at what rpm did this happen?
my guess is above 6000. what most likely happend is you floated the valve. the rpm's get pretty high, and the valve spring doesn't have enough strength to get the valve closed before the piston comes up and smacks it. it happens.

[Cody_300ex]

Same thing happened to my 300ex motor, but I broke both of the intake valves. Tom Clarson said that from running a bigger cam, and h/d valve springs caused the valves to tighten up. He also said when the stock springs were in there the valves wernt going into the head nearly as hard or fast, therefore ripping the valve from the stem. Seamed like a very good explination to me.

[Cody_300ex]

Heres what mine looked like

[Cody_300ex]

piston and valves

[Cody_300ex]

Another of the piston

[YZ400EX]

Yea that does look alot like this motor, but mine has the valve stuck about 1/4" into the head..yours is pretty banged up also. This thing is stuck hard..I cant even get it out with pliers..I have no idea why it happened really..the motor was running fine and then all the sudden it was locked up..The motor wasnt even reving that high when it happened. I want to just buy a new motor and slap it in..This motor was just rebuilt only about 30 hours before this happened..Oh well..I dont wanna spend the time fixing this one..

[Cody_300ex]

Originally posted by YZ400EX
Yea that does look alot like this motor, but mine has the valve stuck about 1/4" into the head..yours is pretty banged up also. This thing is stuck hard..I cant even get it out with pliers..I have no idea why it happened really..the motor was running fine and then all the sudden it was locked up..The motor wasnt even reving that high when it happened. I want to just buy a new motor and slap it in..This motor was just rebuilt only about 30 hours before this happened..Oh well..I dont wanna spend the time fixing this one..

Samething here, I had the idle turned up to about 1/4 throttle to let the battery charge and it ticked real loud, a clunk, and it shut off. One valve was just setting there, and the other stuck in the piston but I pulled it put by hand.