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valve guides - now what?

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I hope you guys can help...

Here is the scoop

2007 CRF250R (bought new last year 2009) Raced one season

approx 40 hrs on motor, would not start, valves had zero clearance

had mechanic take the motor apart, replaced valves (recut with Neway valve cutter system), piston, valve stem seals etc etc... cylinder was minty - not glazed at all... this guy knows his stuff, 50yrs old been doing this all his life.

now when the bike starts after sitting for a period of time it smokes like a 2-stroke for a minute or so then goes away.

buddy drove behind my son and said he could "smell smoke" even though none was "visible"

My question is has anyone had this happen, if so what did you do to fix the problem?

The valve guides are .025mm or .001 inches warn from spec

is this the problem? would that little variance in tolerance cause it to leak oil where it gets burned up and smokes out the exhaust?

Has anyone used Kibble White valves and springs? are they worth the $$??

Should I get a new head? Did Honda fix the valve problems in 2008 or 2009?

Are the heads interchangeable?

Thanks in advance, 👍

Dave

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I don't think .001 is going to make that happen. But, is this on the intake or exhaust guides? The exhaust guides are the ones that normally wear quicker. Valve seals can also give you this issue and so can the rings. My kids bike smokes a little after initial start up but goes away.

I have used the Kibble White in the 450's and they work fine. A bit pricy, but his to his own.

The 08/09 heads are good, but the 07 head is the best unported head to bolt on. The issue with the valves doesn't have anything to do with the valves themselves. It has to do with contaminents (dirt and dust) entering past the filter or through another passage like the airbox/boot seal the makes them wear prematurly. If you haven't already done it, re-seal the boot to the airbox with some hi-temp RTV. On my kids 08, it went 116 hrs on the stock valves without a single adjustment. The only reason I replaced them was because I had to do a second rebuild on the motor due to a crank failure, so while it was apart, I changed them with stock Honda titanium valves. You hear of guys getting 200+ hrs out of the valves and some guys getting 40hrs. My kid is a high level B racer and puts a ton of hard hrs on his bikes. He lives on the rev limiter. The boot to box seal is critical.

Yes, the heads are interchangable.

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Thanks for the help Charlie

Are you sure the valves are Titanium? I heard they are just Titanium Coated...?

This is why they don't last as long and why they are "cheaper" than say Yamaha valves etc.

I was considering changing to Kibbles next valve job because the stock valves only lasted 40hrs

Thanks,

Dave

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The valves are titanium with a protective coating on them. You can go with the stainless steel valves and they will last a long time. But so do the stock titanium valves if you fix the leaks that let in dirt. Personally, I don't care for the stainless valves, but a lot of guys swear by them. I install them for people if that what they want. It's truly a personal preference.

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