Valves

I have a 04 kx250f that needs valves what kind of valves should I use I have been told that stainless steel is the way to go but I don't know I had some one else tell me that they would have to be shimmed a lot

SS valves don't need to be shimmed a lot.  Just get the right springs.  Can't use the OEM springs because they are too light to return the SS valves fast enough.  Are you going to do this yourself?

I am planning on it we have got the bottom end set up right but these valves are giving problems I am tired of having to re shim them all the time

Good news then, because if you have to re-shim them all the time, they would have caused a lot of trouble for you soon.  That is a potentially very expensive deal.  Now is probably a good time.  

 

Know what's less expensive than you might think and worth it?  MXTime.com.  Compare the cost of SS valves and springs to his price and you might be surprised.  Good luck and keep us posted.

I would stay with the titanium valves to be honest. The lighter the valve the better. The less stress on the valve trane the better....

also titanium with heat coating dissipates heat better than stainless.

just my 2 c

I would stay with the titanium valves to be honest. The lighter the valve the better. The less stress on the valve trane the better....

also titanium with heat coating dissipates heat better than stainless.

just my 2 c

 

Al the stress thing is over done and the heat dissipation is more dependent on contact with the seat, right?  I think for the average rider (99%) stainless is a much better option.  Much less prone to unexpected failure.  How many valve drops do we see?  A lot more than valve train disintegration.  In fact, I have yet to see a single case of valve train failure on this or any other thread.  Lots of dropped valves, though.  I respect your opinion, of course, and in theory you are correct, but in practice I see zero harm done by SS valves anywhere.  Not just on TT.  You are in good company with your 2c, but I run SS based on my experience and no way would I go back to Ti.  Not worth it IMHO.

Understand, I have done a lot of work on high performance valve setups for cars that make well over 1000 hp and run up into the 9000 rpm range. We strive to have the lightest toughest valve trane components. Dealing with Valve harmonics, we have found a lighter valve to have better behavior at very high rpm. thus my opinion. Yes I have seen quite a lot of valves drop. mostly due to over reving of the motor and having the engine quickly lug down like on a landing of a jump.

anyway just my 2.5 cents ........

And worth a lot more than that. You make very good points. I think much of the dropping occurs because the OEM Ti valves need good maintenance (oil and air filter as well as proper shimming) and when they start to go, they go fast. Also some invariably get lapped, which is bad. I could see where a motor would rev faster and be more stable at high RPM with Ti. Just have to take care of the bike. I have never dropped either kind and my opinion is not strong on this by any means. Happy with SS so far, but not against Ti for the next valve job. Maybe with alloy seats next time.

Cool info I am trying to find out all I can before I sink a lot of money in the head my son is wanting to race it but I gotta build this head to get ready for him

Just remember SS valves need SS specific springs. Don't over torque the caps. Reset the chain tensioner before you put it back in. Assembly lube or moly on the journals and prime the crap out of it before you fire for the first time. Some have suggested cutting oil grooves in the intake journals, too. "Some" meaning Josh. I miss that guy!

Just remember SS valves need SS specific springs. Don't over torque the caps. Reset the chain tensioner before you put it back in. Assembly lube or moly on the journals and prime the crap out of it before you fire for the first time. Some have suggested cutting oil grooves in the intake journals, too. "Some" meaning Josh. I miss that guy!

You crack me up, lol. Its been an interesting and busy few weeks.

The intake oil grove is simple just match the exhaust grove.

Somewhere there is a graph that shows the strength of SS valves vs. Ti in relation to temperature. I looked briefly earlier but couldn't locate it. It had showed the SS maintaining strength well beyond what the Ti could handle. This was a few years back and I would like to find it again to verify the data.

^^^^ That's what I'm talking about!

Thanks for all the info I have raced oval track for a number of years we used ss valves in all our race heads with a ton of porting and polishing but with these valves I wasn't sure I think that from all that I have heard its going to be costly but at the same time I want it to be right thanks for the info

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