YZ450F Valve blown. Uh Oh!

Hey guys,

So i was out riding a few weeks back now when after about an hour, my bike started to smoke a little.

I didn't know this until my friend told me (he was behind me eating dirt), so I come round a tight corner and give it some throttle, when the revs screamed high and there was a crunch.

At first I thought my piston had seized or something, on later inspection this is the damage:-

 

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So unfortunately, I'm in the process of rebuilding the top end, which should hopefully be done by the end of Jan (fingers crossed).

 

What are your thoughts?

You should replace the crank or have it rebuilt by a local shop with a new rod. Because more than likely the rod has bent from the impact of the piston hitting the valves. Also replace the cam chain, get new cams, and get a new head because it looks totaled, the valve guides are probably oblonged and the the bucket guide looks done for.

Sorry to here about your bike man, that sucks... ):

Edited by Yammer-Hammer

You should replace the crank or have it rebuilt by a local shop with a new rod. Because more than likely the rod has bent from the impact of the piston hitting the valves. Also replace the cam chain, get new cams, and get a new head because it looks totaled, the valve guides are probably oblonged and the the bucket guide looks done for.

Sorry to here about your bike man, that sucks... ):

 

What he said ^ I just got done doing my buddies 08. Everything described above was done or had some damage. He found a deal on a complete head cams and all for 300 bucks other wise it would have been cheeper to part out and buy a new bike. 

 

Good luck.

 

O yeah how does the cylinder look just out of curiosity? His almost survived with out incident except one divot the size of the tip of a ball point pin.

Edited by f150jokerstyle

What he said ^ I just got done doing my buddies 08. Everything described above was done or had some damage. He found a deal on a complete head cams and all for 300 bucks other wise it would have been cheeper to part out and buy a new bike. 

 

Good luck.

 

O yeah how does the cylinder look just out of curiosity? His almost survived with out incident except one divot the size of the tip of a ball point pin.

 

Yeh I checked the crank and it looks fine, it doesn't move apart from a tiny bit of play left and right, but no movement up and down.

Do you still think I should change it?

Yeh I checked the crank and it looks fine, it doesn't move apart from a tiny bit of play left and right, but no movement up and down.

Do you still think I should change it?

Yes it is worth replacing, because there is a possibility that the impact when te piston smashed the valve against the head could have ever so slightly fattened the bottom end needle bearings at the end of the rod, or left indentations in the crank pin or con rods rolling surface, IMO i would replace it. And the crank could also be out of trueness, the runout could be way out of sec, the sudden stopping of the crank, going from like 10,000rpm down to 0 is a second is alottttt of energy and can cause the two crank webs to spin on the crank pin sending the runout out of spec

Yeh I checked the crank and it looks fine, it doesn't move apart from a tiny bit of play left and right, but no movement up and down.

Do you still think I should change it?

 

From what I was told it is a roll of the dice. It could be fine and live a happy life. It could wear out quicker due to bearing damage like mentioned above. Or it could be slightly out of true causing some nasty vibration business. How do you usually end up in vegas? I always leave broke so I know what I would do lol.

 

I still have the crank assembly out of my buddies if you want it for any reason. Crank rebuild I don't know? We were going to have a new rod and big end bearing put on it for fun but due to time restraints on getting it running again we opted for a new OEM crank.

Edited by f150jokerstyle

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