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Broken valve bucket

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Hey guys. So I'm in the middle of rebuilding a 2009 KX250F that is not mine. Long story short the bike has approximately 150 hours on it, its trail ridden mostly,  it went to a dealer to have valves replaced and top end. After that it ran for 4 hours and locked up. It went to a different dealer to be pulled apart (because original dealer would not warranty it) and found that both exhaust valves hit piston,the right exhaust valve bucket is broken in half and the valve stem is mushroomed with 1 of the keepers pushed up. So now I'm stepping in to fix this bike right the first time. Basically the dealer just thought either the valves were adjusted to tight or the timing was off. I'm planning on doing a complete top and bottom rebuild. The head is damaged pretty bad where that bucket sits but looks good everywhere else. The cam chain is kinked bad at the crank but I'm not sure if this happened when it locked up. I do not think the dealer replaced the cam chain, which could be our whole problem. What do you guys think? What have you guys seen cause bucket failures like this? Do you think I can send the head out to be repaired or just buy new, I'm thinking MX Time? I'm trying to save money on this job but also do it right. Any opinions please feel free!   

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Hey guys. So I'm in the middle of rebuilding a 2009 KX250F that is not mine. Long story short the bike has approximately 150 hours on it, its trail ridden mostly,  it went to a dealer to have valves replaced and top end. After that it ran for 4 hours and locked up. It went to a different dealer to be pulled apart (because original dealer would not warranty it) and found that both exhaust valves hit piston,the right exhaust valve bucket is broken in half and the valve stem is mushroomed with 1 of the keepers pushed up. So now I'm stepping in to fix this bike right the first time. Basically the dealer just thought either the valves were adjusted to tight or the timing was off. I'm planning on doing a complete top and bottom rebuild. The head is damaged pretty bad where that bucket sits but looks good everywhere else. The cam chain is kinked bad at the crank but I'm not sure if this happened when it locked up. I do not think the dealer replaced the cam chain, which could be our whole problem. What do you guys think? What have you guys seen cause bucket failures like this? Do you think I can send the head out to be repaired or just buy new, I'm thinking MX Time? I'm trying to save money on this job but also do it right. Any opinions please feel free!   

Pics would be good Boss. Like they say a pic is worth a thousand words. 

 

  My guess is the bucket got broke (VERY RARE) because everything bound up. The piston forced the valve up against the cam breaking the bucket. I would suspect that the cam is also bad, though it may not look like it. 

 

  The problem is I don't believe you can get oversized buckets. If you could it could be machined to accept a larger bucket and fix the damage that way. 

 

  Really hard to say without seeing it though.  Might be better off starting over with a complete used cylinder head. 

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Pics would be good Boss. Like they say a pic is worth a thousand words. 

 

  My guess is the bucket got broke (VERY RARE) because everything bound up. The piston forced the valve up against the cam breaking the bucket. I would suspect that the cam is also bad, though it may not look like it. 

 

  The problem is I don't believe you can get oversized buckets. If you could it could be machined to accept a larger bucket and fix the damage that way. 

 

  Really hard to say without seeing it though.  Might be better off starting over with a complete used cylinder head. 

Thanks for the reply. Yeah I didn't post pics because I know the area of the head at the bucket needs repaired(its tore up), just curious of what you said about machining it and putting a over sized bucket in there. I would definitely be interested in a good used head, but so far I could not find one. A new head then installing valve train is going to run us about 900. Yeah the exhaust cam has wear on the lobes also, so its gonna get a set of hot cams stage 1. I'll probably post some pics when I get time. 

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You might take some high quality pics and send them in an E-Mail to APERACEPARTS.com. 

 

  It's always possible that it could be welded up and then machined back to original size, but that would be a LOT of work by some very skilled people and not be cheap. 

 

  Broken buckets are very unusual.   

 

  And just to be clear the bucket is the polished piece that sits under the cam and above the valve shim.  I assume that broke and then really did a number on the bore which it was resting in. 

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You might take some high quality pics and send them in an E-Mail to APERACEPARTS.com. 

 

  It's always possible that it could be welded up and then machined back to original size, but that would be a LOT of work by some very skilled people and not be cheap. 

 

  Broken buckets are very unusual.   

 

  And just to be clear the bucket is the polished piece that sits under the cam and above the valve shim.  I assume that broke and then really did a number on the bore which it was resting in. 

Yup that is the bucket I'm talking about. Yeah it did a number on the bore for sure. the rest of the bucket is stuck all the way down the bore. Its strange because the dealer that did the valve job billed out 1 new bucket. I find that strange and maybe coincidental. The other exhaust valve bucket is not polished, more of shiny black. I assume this is the new bucket. Makes me wounder what was wrong with that bucket and why not replace both. Idk. weird. Yeah im kind of worried that it will cost more to have repaired then just buying new and have a good feeling about it. 

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That head is trash Boss.Sorry. 

Yeah thats what I kinda figured, same with the rod.Junk. Its a shame but stuff happens. Time to do it right. Its just hard to tell what failed first, the bucket or timing. Makes me curious, I might slap the top together as is to see if the timing chain is stretched or maybe the tensioner took a poop, but regardless chain is getting replaced. 

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Yeah thats what I kinda figured, same with the rod.Junk. Its a shame but stuff happens. Time to do it right. Its just hard to tell what failed first, the bucket or timing. Makes me curious, I might slap the top together as is to see if the timing chain is stretched or maybe the tensioner took a poop, but regardless chain is getting replaced. 

I can promise the bucket did not fail on it's own. 

 

  And in reality there is a fairly small window for valve timing that will let the engine start. 

 

  I would have to assume there was a failure upon assembly. Like the shim was not properly seated into the valve tip. 

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