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1996 XR250R valve guides

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I seem to have issues with the valve guides in the cylinder head leaking oil past them and causing a lot of smoke. I pulled the exhaust header pipe off and one of the pipes has a lot of burnt oil/carbon built up in it. The other one looks fine so I knew it has something to do with the one exhaust valve, seal, or guide. I started it up without the pipe on and I could see the end of the guide moving around, so it has to be loose. I pulled the cylinder head off and took the valve out and I could slide the guide up and down by hand and those guides should be pressed in pretty tight. I'm sure the oils is just leaking down around the guide. 

Ok, my question is when I look up the guides on-line they say over sized so does that mean the outside diameter of the new guides is larger than the original ones so I can replace them and the new one will be tight?  If they are oversized then I assume I will need to make the hole in the head a little bigger with a reamer or something right?  Does anyone know what the outside diameter of the oversized guide might be?  I do know from about 7 years ago when I replace the other guide that the new guides have to be reamed out with a 5mm reamer otherwise the valve won't fit through it but I don't remember seeing that the new guide was oversized. 

Anyone know what part of the new guides are oversized and how much oversized are they so I can figure out if I can install a new oversized guides? Maybe I should just get a new cylinder head instead with all new guides and head. I'm not sure what to do. 

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I have a similar problem, not exactly. Mine had a cracked head, between the spark plug threads and vavle seat. One seat was falling out. it seems this is, was, common. the 96 head has smaller stems on its valves. the earlier valves were 5.5. Many think the head comes without the guides bored to the right size, but the intent was to use a smaller stem.

if the guide is loose in the head, I would take it to a head repair service, and ask them if its repairable. New parts, might be your best, and maybe cheapest solution.

'96 head was a spec change, in the last iteration of its part nomenclature. head # 12200 KCE 672, also takes the KCE 5mm stem valves. This head has the 10mm thread spark plug, not the original 12mm spark plug. the smaller thread, allows for more material and I assume a better quality head. last pic is new spec head. I bought a new head.

 

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I will answer my own question. I ordered new guides and measured them. They are just a little bigger around so the new guide is nice and tight in the cylinder head. I replace the o-ring under the guide and had to use a 5mm reamer to open the center of the guide up so the valve would fit through the new guide. I already had the reamer from the last time I had this thing apart. Don't ask me why they don't come in the right size? I used a little valve lapping compound on the valve and seat. Should be good to go now. 

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