Checking Valve clearance on CRF250

gharmon
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gharmon
Edited Date/Time 6/5/2014 5:29pm
I have a 2007 CRF 250 that I have no history of previous ownership. The bike had enough aftermarket stuff to either belong to someone who just had money to throw around or someone that was possibly a privateer (I believe the latter). Anyway, I do know the bike as stage 2 hotcam. As far as internals, I do not know. I have previously owned a 04 and 08 Crf 250's and this bike is much much stronger.

My dilemma, upon checking the valves the intakes are fine and within spec, maybe a .001" tighter that spec. The exhaust is a different story. They have zero clearance. Now I know on my previous bikes this meant you probably had let them go too long and would need a valve job minimal. But when looking to try and put a smaller shim in they already have the smallest shim made. they are actually below the surface of the valve retainer. This would suggest the tip of the valve stems have worn down too small? The followers/rockers are actually riding the valve retainer so no size shim would matter as they are recessed below the retainer height?

Any ideas? I have no idea what type of valves, seats or keepers are in the head. There is none of the typical issues related to bad clearances. i.e. hard starting. Could the tips just be worn or could they have been manufactured with a shorter tip (above the keeper grooves) than say a stock valve?

Thanks guys.
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Paw Paw 271
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Paw Paw 271 6/3/2014 2:21pm
6/3/2014 2:21pm
Hot cams normally suggest a tighter that oem spec's on the valve clearances. I have found that using the OEM clearances works the best even on Hot Cams products.
The exhaust valves seem to be the main issue here. If the smallest shim is still too big then you need to tear it down and have the head examined and then fixed. What you have on the exhaust valves is not good and could fail at any time. If that happens you will be out a lot of money to fix if fixable, so don't let that happen. Fix it now.

Paw Paw
Socket946
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Socket946 6/3/2014 2:43pm
6/3/2014 2:43pm
gharmon wrote:
I have a 2007 CRF 250 that I have no history of previous ownership. The bike had enough aftermarket stuff to either belong to someone who...
I have a 2007 CRF 250 that I have no history of previous ownership. The bike had enough aftermarket stuff to either belong to someone who just had money to throw around or someone that was possibly a privateer (I believe the latter). Anyway, I do know the bike as stage 2 hotcam. As far as internals, I do not know. I have previously owned a 04 and 08 Crf 250's and this bike is much much stronger.

My dilemma, upon checking the valves the intakes are fine and within spec, maybe a .001" tighter that spec. The exhaust is a different story. They have zero clearance. Now I know on my previous bikes this meant you probably had let them go too long and would need a valve job minimal. But when looking to try and put a smaller shim in they already have the smallest shim made. they are actually below the surface of the valve retainer. This would suggest the tip of the valve stems have worn down too small? The followers/rockers are actually riding the valve retainer so no size shim would matter as they are recessed below the retainer height?

Any ideas? I have no idea what type of valves, seats or keepers are in the head. There is none of the typical issues related to bad clearances. i.e. hard starting. Could the tips just be worn or could they have been manufactured with a shorter tip (above the keeper grooves) than say a stock valve?

Thanks guys.
Going to need a valve job on the exhaust side. May as well get all 4 done.
Paw Paw 271
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Paw Paw 271 6/4/2014 3:36am
6/4/2014 3:36am
the exhaust valves have stretched and that is why they can't be shimmed now. They need to be replaced before they break.
circus
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circus 6/4/2014 6:05am
6/4/2014 6:05am
Yup, all of the above is correct. Reread Paw Paws last sentence, THEY NEED TO BE REPLACED BEFORE THEY BREAK!

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gharmon
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gharmon 6/4/2014 10:10am
6/4/2014 10:10am
Yeah I been have flashbacks since checking the valves. I was jumping some rather large hills at Monster Mountain Sunday and I cringe to think what could of happened had it dropped a valve at that time. Hate to bring up an old topic but I believe that's exactly how Chase Borders became paralyzed at MM a few years ago. Heck he was even riding around in his chair at the track Sunday. Creepy just thinking about it.

In case the seats and shit need to be done, who do you guys recommend for doing me a solid valve job? I'm looking for quick turnaround but still quality work. Is price an option? Sure. But just prefer a quality valve job with decent turnaround time.

Thanks
DTHA70
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DTHA70 6/4/2014 1:37pm
6/4/2014 1:37pm
Paw Paw 271 wrote:
the exhaust valves have stretched and that is why they can't be shimmed now. They need to be replaced before they break.
valves dont stretch, they receed into the head and lose their sealing surface. but regardless, youll need new valves and seats, im going to give a shout out to charlie at pro 1 racing heads to send your stuff to. dude is a guru and does beautiful work.
DTHA70
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DTHA70 6/4/2014 1:40pm
6/4/2014 1:40pm
and stick with either OEM or delo west valvetrain components., del west are a little more pricey, but end up saving some weight and last longer. stay on top of air filters and oil like your life depends on it and they wont move. had 400 hrs on the stockers on my full mod 450 before i replaced with del west stuff and moldstar 90 seats and guides all around just for the heck of it. keep that filter clean and your oil fresh and theyll outlast the rider lol.
Paw Paw 271
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Paw Paw 271 6/5/2014 5:29pm
6/5/2014 5:29pm
I don't want to be a butthead here, but the valves will "Streatch" and the head of the valve will cup. Both effect the valves seat height and cause you to not be able to shim them. The seats can also wear doing the same thing. The end result is that they need to be replaced before they break.

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