crf 250 valve ?

[dirtbikr99]

This is a tricky question....

I will have to do two 2007mcrf250 top end rebuilds.

I ordered oem piston stuff and gaskets. I also ordered oem timing chain.

I am unsure of how I want to go on the head. I will leave the exhuast valves alone. I was thinking of going with steel intakes as well. The sole purpose of these bikes will be riding on concrete jumping ramp to ramp everyday.

I was thinking the steel valves would last longer. Then I started reading about how its heavier and can put more stress on the valve seat. catch 22.

I would order kibblewhites intake steel kit if no one said, DONT USE STEEL VALVES.

BUT this is where it gets tricky, I work for a company..bla bla bla ....I have to pay for the parts myself! My freinds will be jumping the bikes ramp to ramp. I want too obviously keep costs down.

I hear the fraction steel valves are no good???
THEN I saw pro x steel valve kits CHEAP. But I dont think there stainless, I read nitrate coated. Are the pro x going to be terrible? I want to use these because of the cost and because they will last longer than the stock ti.

Thank you for the help. I will be ordering some valves tomorrow...

 

[dirtbikr99]

I just read the pro x are stainless then coated. Why would pro x coat them and kibblewhite and fraction not?

 

[_JOE_]

Kibblewhite sets the standard for steel valves. As long as you have the seats properly machined and use the KW spring kit they'll outlast pretty much any valve out there. You may notice a bit less over rev with the slightly heavier steel valves.

 

[dirtbikr99]

I know they do. haha But it would cost me $160 more out of my pocket for those valves. :(

 

[Rich Rohrich]

I know they do. haha But it would cost me $160 more out of my pocket for those valves. :(

The valvetrain is an idiotic place to try and save money by using sub-standard components.

 

[dirtbikr99]

sigh....

Thank you so much for responding Mr. Rohrich. Can you recommend intake valves for my purpose? Stock oem ti? KW stainless?
:ride:

 

[Rich Rohrich]

Joe gave you the best advice you'll get. Go with the complete Kibblewhite kit. Use their stainless steel valves and the full Kibblewhite spring kit. You can't cheap out on the springs by using OEM or junk springs that get sold at a discount on e-bay.

Get someone qualified to do a good valve job and have them assemble the head correctly with those parts and you'll never have to worry about the valves. All you'll ever have to do is check the clearances once or twice a year.

 

[dirtbikr99]

Thank you guys.

 

[Matt90GT]

just buy a new head:

http://bigborethumpers.com/newheads.html

ready to run with SS valves

 

[dirtbikr99]

Hey guys, I'm over here in china. I got a look at everything. There are two 2009 crf 250's a 2007 and a 2008.

The 2007 was just rebuild before i got here.

The 2008 runs good so I will probably rebuild that top end.
No hour meter so I dont know how long its been.

I checked the valve clearances on the 2009, they were perfect. Bikes runs good.

The other 2009 has low compression and is hard to start. I checked the valves, hoping they were be out of spec. They are still in perfect spec. The bike has exactly 17 hours on it. This leads me to believe it needs a new piston. I checked the part number is the same for 2007/08 and 2009 piston. So I can use the extra parts I brought with me.So 2007/08 and 2009 top end parts are all interchangeable? I just hope the plating is in ok shape. :bang:

Does the 2007 or the 2009 have better porting?

Are the "collers" thingys that hold the cam down interchangable between heads? I brought my 2005 with me I want to switch it with the 2007 head for the better porting but I forgot to bring my 2005 "collers."

thanks

 

[_JOE_]

There were not interchangeable on my 06. They were machined together with the head. I would bet the newer models are the same.

 

[dirtbikr99]

Yeah, thats what my mechanic buddy told me once. I was keen on thats 2007 head.

 

[_JOE_]

What happened to the caps for that head?

 

[dirtbikr99]

Left them back at home, by accident.

 

[Ol'89r]

If money is an issue and you don't want to spend the extra for the Kibblewhite valves then, simply replace the bad valves with stock valves. If all you are doing is ramp to ramp jumping, the stock ti valves will last a long time. Check on the Service Honda link for discount prices.

Like Rich suggested, have someone that is experienced in head work do your valve job. It is very important that the seats are cut correctly and the valve springs should also be checked for proper tension.

 

[dirtbikr99]

Thanks for the reply 89r.

I have all the parts here with me already. I'm the guy here doing the work. I'm no pro, but I'm here with the correct tools a manuel, and a decent amount of experience with a pro mechanic. I have been advised (PRO mec.) when switching to stainless valves its not really needed to cut the valve seats. I also have new springs.

I should have brought an extra cylinder with me. I think the plating is going to be bad on that 2009.

I know the valve "CAPS" (for the camshaft) are machined for each individual head. In a pinch can you use calve caps from a different head?

 

[Ol'89r]

Thanks for the reply 89r.

I have been advised (PRO mec.) when switching to stainless valves its not really needed to cut the valve seats. I also have new springs.

I know the valve "CAPS" (for the camshaft) are machined for each individual head. In a pinch can you use calve caps from a different head?

It doesn't depend on what kind of valve you are going to use, it depends on the condition of the valve seat. The valve seat can look good to the naked eye but it can be pounded into the head unevenly. You can't tell that by just looking at it you can only tell by cutting the seat or lapping the valve. It's not recommended to lap the ti valves. If I were you I think I would find another PRO mechanic. ;)

The cam caps do not interchange. Using cam caps from a different head could result in seizing your cam. The cam caps are line-bored for each individual engine.

Also, if you are going to use stainless valves, you can't use the stock springs. The stock springs don't have enough tension for the heavier SS valves. That is why you have to buy the Kibblewhite spring kit when using the Kibblewhite SS valves. Using the wrong springs on SS valve can cause your valves to 'float'. Valves that 'float' have the possibility of hitting your piston. That can result in a very expensive problem.

There again, I would recommend having someone with the proper experiences and equipment do your head. Unless you know how to cut the seats and have the equipment to do so, you are taking a big chance of messing up your head.

Your cylinder can be replated. Check with Millennium Technologies.com.

IMO, it's best to use the right stuff. Trying to save a little money at this time could cost you a whole lot of money later.

 

[Ol'89r]

In a pinch can you use calve caps from a different head?[/B]

In some cases the cam can be lapped into the cam caps. Most of the heads are machined pretty close to one another. There are cutting/lapping compounds available that you can use to lap the cam into the caps. They will cut about .001" clearance and then stop cutting. Once the cam is lapped into the caps, the cam has to spin freely in the caps. Any resistance on the cam can cause it to seize in the caps.

 

[Rich Rohrich]

I have been advised (PRO mec.) when switching to stainless valves its not really needed to cut the valve seats.

Next time you see that guy coming with advice RUN the other way. If he's a professional mechanic then I'm the King of Venus.
That is idiotic advice at best.

The advice 89r gave you is the approach you should take. Trying to half-ass the valvetrain on an engine capable of 13,500 rpm is a great recipe for an expensive blow up.

 

[dirtbikr99]

Thanks for all the reply's guys! I know you guys have alot of knowledge.

I'll let you know how it goes.

The mechanic who told me about not needing to cut valve seats going to stainless valves, on a head thats still in good condition is very good. The guy is like 50, been doing this stuff for ever. Works on bikes almost 9 hours a day.

 

[whenfoxforks-ruled]

Age is a poor excuse for not learning.

 

[Ol'89r]

The mechanic who told me about not needing to cut valve seats going to stainless valves, on a head thats still in good condition is very good. The guy is like 50, been doing this stuff for ever. Works on bikes almost 9 hours a day.

Good luck with that. :cool: ;)