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50 hours out of a set of Kibblewhites?

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This doesn't seem right to me.  I bought an 05 crf250x in November.  A couple rides later it wouldn't start.  I knew going into it the issues these have with valves.  So I knew where to look.  I did my research and didn't even bother re-shimming them.  Once they start to wear, they will need to be replaced soon.  So I ordered a set of Kibblewhite stainless intake valves and springs.  I had a machinist (a highly recommended one) reseat the head and install everything.  I slapped it back together, along with a new piston and rings,  and double checked the clearance.  Spot on.  About 10 hours later I checked it again and it had tightened up.  So I reshimmed it.  Spot on.  Now I am at about 50 hours and I had starting issues after my oil change yesterday.  So I pulled the cover and checked.  They were zeroed out.  I plan on going to the shop in the morning and picking up some shims.  But I'm worried that my kibblewhites are worn. 

 

Blah blah blah...   To my questions

 

Is it the same case with the KB's as the stock ti valves?  I was to understand that I would have to possibly adjust after break in, and they wouldn't move much after that.  Are these going to start failing quick now?  Am I about to invest in another set?  Or am I good to just re-shim it as necessary?

 

By the way, I keep up with my maintenance.  Oil and filter change after every other ride, usually after every ride.  Clean and oil air filter after every ride. Carb side of air box is clean.

 

Thanks,

 

Rich

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Rich,

 

  You've got something else going on; stainless steel holds up very well, certainly much more then 50 hours.

 

  Sounds to me like the new valves were not fitted properly.  To do so requires cutting the seats on three different angles to ensure that the full face of the valve meets the seat.

 

Jim.

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Were the seats cut or did he just lap the valves in?

 

Normally the KW's last much longer, is that the original head and do you know if those seats have been cut or how many times theyve been cut?

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250-300 hours out of KW is more common than 50. Something didn't go together right.

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For what it is worth, I had the same out of some Pro-X valves.  Two shims in the first six months, but then they have been set for the last year plus.  It probably had 50 hours in that 6 months and things have been good sense.  It makes no sense, but I check them every three months or so and they are still spot on.  Its one of those things I can't explain, but as Eddie Hill said back in his days of racing, If it ain't broke, don;t fix it.

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Sorry to hijack, but this post concerns me as I just installed KW valves into a new head. I started my own thread about this and no one mentioned having to have the seats cut on a new head to fit the SS valves (per Jim's post above). Before I go putting everything back together, do I need to have the seats cut on a brand new head to match the valves? I would hate to have this same issue after just 50 hours.

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Well f-me! I just went back to my thread and somehow I missed a few recent posts, one in particular that specifically addressed the same question - the answer being 'yes, new head absolutely needs to be machined for the new valves". Guess I'll be taking it apart and finding a machine shop...

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Well f-me! I just went back to my thread and somehow I missed a few recent posts, one in particular that specifically addressed the same question - the answer being 'yes, new head absolutely needs to be machined for the new valves". Guess I'll be taking it apart and finding a machine shop...

 

Most guys get a new head and install the new SS valves, springs etc without having any seat work done, but may lap the valves in.

If you were going to have the seats cut you might just as well have it done to your old head instead of buying a new one. 

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spoke with two local shops yesterday that have been around for a while and have good reputations. Both didn't think there was a need to cut the seats on a new head to match the new valves (and NEVER lap them in). This was also explained in this video - https://www.youtube.com/watch?v=c_-n20Op1j0. One of the guys also told me to throw the kibblewhites in the trash, lol. He had a very strong opinion about their quality and said he's seen enough of them "pop their heads right off like popcorn". I've not come across this opinion anywhere else, and i'm sure they'll be more than fine for the riding I do. He did go on to stress the absolute importance of proper air filter maintenance. Had me explain how I cleaned my filter, and then broke down how he feels it should be done. Good advice that I'll be following strictly once I get everything installed.

 

Sorry to the O/P for taking over this thread a bit.

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Both didn't think there was a need to cut the seats on a new head to match the new valves (and NEVER lap them in).

 

 Yes, your pretty safe on a new head,  but you should always check it anyway. I think though we've gotten a bit mixed up; it sounded to me like Rich had an old head with new valves.  If you had a new head and valves, then you really don't have any worries.

 

  As for the *never* lap in, that really is only true for titanium.  They have a coating on the valve face that you do not want to wear through for any reason. 

 

  But any valve that doesn't have a coating can be lapped. I'd only do that however if the imperfection was very small and you had good contact across the face already.   Cutting the seat will always give you the best possible fit and the longest valve life.

 

Jim.

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Didn't see anything mentioned in the OP about checking the guides. Even fresh cut seats will chew up a set of valves if the guides are out of spec. The worn guides let the valves move around too much as it is coming back onto the seat.

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Didn't see anything mentioned in the OP about checking the guides. Even fresh cut seats will chew up a set of valves if the guides are out of spec. The worn guides let the valves move around too much as it is coming back onto the seat.

 

+1, I was thinking the same thing. On a new head, no worries. On a used/rebuilt head, a absolute must do!

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GBE machinist cut the seats and replaced the guides. HD springs on the intakes and new OEM replacements on the exhause valves.

I went ahead and reshimmed. Runs good. I hope it lasts. That's an awful lot of money to spend on 50 hours.

And no worries about the hijacking. Info is info. If a couple of us can get some questions answered, that's even better.

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When I changed from Ti to stainless, the valve seats needed to be changed. Cause the valve seats used with Ti are softer than the seats used with stainless to help with wear on the Ti, and if you use the seats that are designed for Ti with stainless valves they wear out faster due that they are softer which leads to the valves closing up.

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