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Dropped a valve

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Well, here is the issue.....

My son's buddy bought a 'well-used' 250F a few weeks ago. Last weekend he finally got a chance to head out to the desert and ride. After a couple of hours it 'locked up'. He called me to ask if he could bring it to my house to take a look at it. How could I refuse? :banghead: (His parents are not that crazy about him riding anyhow and 'allow' it only because his closest friend ride too... namely my son :applause: )

Tonight, we finally had a chance to tear into the beast and found the left intake valve had dropped. Conveniently, it positioned itself upsidedown under the left exhaust valve. This resulted in the dropped valve stem being 'punched' through the piston crown and the exhaust valve bucket/spring and cylinder head destroyed...along with the exhaust cam.

So, at a minimum, I see the need to replace:

1. Cylinder Head/Exhaust Cam

2. Valves and associated parts

3. Piston & Rings

Of course this is NOT going to be cheap! 🤣

After reading some of the posts about this type of 'issue' I am wondering if it is even worth fixing. Would he be better parting the bike out and starting over? Or is there something I can do to help him out? I hate to see a 16 year old looking at his bike on the stand while his buddies are loading theirs into the truck to go ride. 🤣

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what year is the 250f?? 01 or 02 you might seriuosly think about parting it out

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It is an '02. (Had that in the text, but must have lost it when I tried to create a bulleted list)

'Parting it out' was not the answer I was hoping for, but was expecting.

Thanks.

(Anyone else have a silver bullet for me. <grin> )

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I all you need are the parts listed, it may be worth fixing. The question would be if the bottom end is in good shape and the condition of the rest of the bike. If it punched a hole in the piston then there is metal in places it shouldn't be. Still, if you are mechanically inclined enough to do a whole tear-down it would likely be worth it.

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dknstormy,

sorry to hear about your situation.

you need to include a new crank (w/rod) assembly in your parts bill. might as well put new crank bearings as well. cam chain too.

that adds about $240+ to the bill. gonna take close to 1k to make it fully functional again.

is there any indication as to WHY it dropped the valve to begin with?

p.s. silver bullet would be a "new" 05 you find someplace cheap. or a very very good used 03-05.

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Well, here is the issue.....

My son's buddy bought a 'well-used' 250F a few weeks ago. Last weekend he finally got a chance to head out to the desert and ride. After a couple of hours it 'locked up'. He called me to ask if he could bring it to my house to take a look at it. How could I refuse? :banghead: (His parents are not that crazy about him riding anyhow and 'allow' it only because his closest friend ride too... namely my son :applause: )

Tonight, we finally had a chance to tear into the beast and found the left intake valve had dropped. Conveniently, it positioned itself upsidedown under the left exhaust valve. This resulted in the dropped valve stem being 'punched' through the piston crown and the exhaust valve bucket/spring and cylinder head destroyed...along with the exhaust cam.

So, at a minimum, I see the need to replace:

1. Cylinder Head/Exhaust Cam

2. Valves and associated parts

3. Piston & Rings

Of course this is NOT going to be cheap! 🤣

After reading some of the posts about this type of 'issue' I am wondering if it is even worth fixing. Would he be better parting the bike out and starting over? Or is there something I can do to help him out? I hate to see a 16 year old looking at his bike on the stand while his buddies are loading theirs into the truck to go ride. 🤣

Not that your failure is just like this one: https://thumpertalk.com/forum/showthread.php?t=294173&parentpage=3

but, it gives you an idea as to how fixing a blown 250F engine is generally like opening up a can of worms. The farther you dissasemble the engine, the more money it costs to repair.

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I have a good motor for sale out of my 03 yz 250f. It was rebuilt once, because the crank bearing seized. The motor is in really good condition and it doesn't have a crapload of hours on it. I change the the oil about every 6-8 hours and I run Amsoil. The reason I change the oil so much is because I can't afford a catastrophic engine failure like what happened to you. If your interested in buying it send me a PM. Thanks alot

quote from dknstormy "I hate to see a 16 year old looking at his bike on the stand while his buddies are loading theirs into the truck to go ride."

BTW I am 16 and I am the kid you are talking about.

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I am not really sure why the valve would have dropped. Looking at the amount of wear on the frame and crankcase covers, I'd say it has a LOT of hours on it. That is probably 'nuf said. :banghead:

I hind sight, I wish he had taken me with him when he originally looked at the bike. I would have likely told him to keep looking.

Also, it looks as thought the piston may have been replaced VERY recently. The cylinder walls still show honing marks and the top of the piston has markings of: PROX 04-03. I am guessing this is not stock. (I did mic the cylinder and it is still stock - 77mm)

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I believe kibblewhite stainless valves and springs are cheaper than yamaha stuff. They are 1 piece also and will last longer than the the stock valves which is a really long time. I would have the head repaired. It will be a heck of a lot cheaper than a new one. Also check the connecting rod to see if it is bent. I had an 05 do the exact same thing about 2 months ago. Hopefully this was of some help. -Curtis

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I am not really sure why the valve would have dropped. Looking at the amount of wear on the frame and crankcase covers, I'd say it has a LOT of hours on it. That is probably 'nuf said. :banghead:

I hind sight, I wish he had taken me with him when he originally looked at the bike. I would have likely told him to keep looking.

Also, it looks as thought the piston may have been replaced VERY recently. The cylinder walls still show honing marks and the top of the piston has markings of: PROX 04-03. I am guessing this is not stock. (I did mic the cylinder and it is still stock - 77mm)

It can really result from one issue, that being a broken valve spring, which allows the split valve keepers to become dislodged, and the valve drops into the cylinder.

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in one of the last posts (by D.N.E.) he said to get the head repaired. who repairs them??? i need a valve seat replaced

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get a honda

You own a WR, and you come up with this comment? Are you just shooting off your mouth for no real reason?

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