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Yamaha valve spring differences...

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Hi,

The valves on my '07 WR250F are nearing the end of their life and i'm assessing my options for refurbishing the head. You can buy all new genuine valves, springs and seals from eBay in the states which is the cheapest option for parts. The catch is they are for a YZ250F.

The part numbers for everything but the valve springs are the same, leading me to think they must have different spring rates between the YZ and WR's which is why they have different part numbers.

Part numbers:

WR: 5NL-12116-00-00 INTAKE VALVE SPRING

3GM-12126-00-00 EXHAUST VALVE SPRING

YZ: 5NL-12113-00-00 INTAKE VALVE SPRING

5NL-12114-00-00 EXHAUST VALVE SPRING

So, my question is can anyone tell me what the difference is between the YZ and WR springs? Can i just use the YZ ones when i rebuild the head on my WR?

Thanks,

Ryan.

Edited by Ryan250f

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Unless you are planning to switch to heavier stainless valves, you should have no problems reusing your stock valve springs.

I would assume the difference between the YZ and WR spring part numbers is the seat pressure. Aftermarket spring kits make no distinction between th YZ and WR.

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I will be definatley be using new springs with the new valves.

Talking of head re-builds, is there anything else in the valve train that should be replaced apart from valves, springs, seals and having the new valves cut into the head?

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Im sorry but thats bad advice telling him to re-use 5 year old springs. Valve springs are so cheap they should be replaced when ever the top end is rebuilt.

Granted that springs made 40 years ago may be made from inferior materials when compared to modern springs, the following applies to the OP's bike;

Cotrrary to popular belief, high quality springs (which OEM Yamaha can be considered) don't 'wear out'. There is a greater likelyhood that a new spring will fail than a spring that has been in service for some peiod of time.

The only time it should be considered mandatory to replace valve springs is if the engine has been subject to severe overheating.

Most professional engine builders wont install brand new spings in an engine without doing a 'run in' on a dyno mule in order to weed out springs that will fail.

I can hardly see advising to reuse valve springs as "bad advice" when it's a very common practice in every rebuilding shop (automotive AND motorcycle).

Maybe a better way for you to make such a statement is to suggest that the original springs be checked for seat pressure before being re-used.

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Granted that springs made 40 years ago may be made from inferior materials when compared to modern springs, the following applies to the OP's bike;

Cotrrary to popular belief, high quality springs (which OEM Yamaha can be considered) don't 'wear out'. There is a greater likelyhood that a new spring will fail than a spring that has been in service for some peiod of time.

The only time it should be considered mandatory to replace valve springs is if the engine has been subject to severe overheating.

Most professional engine builders wont install brand new spings in an engine without doing a 'run in' on a dyno mule in order to weed out springs that will fail.

I can hardly see advising to reuse valve springs as "bad advice" when it's a very common practice in every rebuilding shop (automotive AND mo

Maybe a better way for you to make such a statement is to suggest that the original springs be checked for seat pressure before being re-used.

2grim, are you sure about this as it's been pretty common advice to change the springs often. I've changed mine during every top end rebuild just as a caution.

Your point is valid, though, as all the spring is required to do is meet a certain spec.

I'd like to see more details on this if possible.

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In 2010 the YZ's got aluminum valve retainers and softer springs, supposed to make the engine rev better and the vavle train should last longer in theory. Softer spirngs would mean less wear on the seats, the cam lobes, and the cam chain. I put them in my 06 yz when I did the rebuild. I weight the parts before I put them in, the Aluminum retainers were about half the weight of the steel ones and the new springs were a little lighter to. It was only a few grams if I remeber right but when its turning 13500 rpm It probably does make a difference. I'm not a physisits so I wouldn't realy know but It might be worth going with those if your going to go with the YZ ones any ways. I wonder if they didn't put softer springs in the WR cause they fiqured it wouldn't see the RPMs that a YZ does and it would extend the life of the seats.

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Just for anyone wondering.

When i originally inquired about the part numbers the guy I spoke with gave me the wrong ones.

So in fact, the valve springs for the YZ and WR are the same. Easy, problem solved! :smirk:

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if you go buy the book the springs are good until they dont meet thier free length specs.

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Not to change the subject, but can anyone tell me the exact weight difference between a SS and titanium valve?

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if you go buy the book the springs are good until they dont meet thier free length specs.

May be correct.

If you think about reliability statistics, a used spring that still meets it free length spec, may be less likely to fail than a new spring.

Most spring fracture failures are due to manufacturing errors and material flaws and may follow the classic "bathtub" statistical failure curve. That shows that the failure rate is high for the initial "infant mortality" period of use and then drops to a low value for an extended period of time until it increases again due to material "fatigue". That means if you have run springs for a year or two you are beyond the "infant mortality" period. When you install new springs wouldn't you have to go through this infant mortality period again, unless the manufacturer tests every spring for an extended period of time?

Then, the next question is the "fatique" period at the end of the bathtub curve. If your spring has taken a set, then maybe that's an indication of too many cycles. If they have not taken a set, then maybe that indicates that they are not nearing the end of their life, yet?

Anyway, it's really an emotional issue. It just "feels" better to me to install new springs, and they are inexpensive, so why not do it? The only reason I can think of is "infant mortality", if my assumption is correct that the manufactures do not screen each spring for extended time periods then I may be increasing the probability of failure. But, maybe they do a test screen on the springs?

Edited by Sofiedog

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May be correct.

If you think about reliability statistics, a used spring that still meets it free length spec, may be less likely to fail than a new spring.

Most spring fracture failures are due to manufacturing errors and material flaws and may follow the classic "bathtub" statistical failure curve. That shows that the failure rate is high for the initial "infant mortality" period of use and then drops to a low value for an extended period of time until it increases again due to material "fatigue". That means if you have run springs for a year or two you are beyond the "infant mortality" period. When you install new springs wouldn't you have to go through this infant mortality period again, unless the manufacturer tests every spring for an extended period of time?

Then, the next question is the "fatique" period at the end of the bathtub curve. If your spring has taken a set, then maybe that's an indication of too many cycles. If they have not taken a set, then maybe that indicates that they are not nearing the end of their life, yet?

Anyway, it's really an emotional issue. It just "feels" better to me to install new springs, and they are inexpensive, so why not do it? The only reason I can think of is "infant mortality", if my assumption is correct that the manufactures do not screen each spring for extended time periods then I may be increasing the probability of failure. But, maybe they do a test screen on the springs?

Speaking of a springs free length, I reluctantly overlooked a few things myself, because I was specifically told on this site that springs work through their entire length whether they are progressively wound like in our cam chain tensioner or just compressed such as in our valve cavities. This led me to further investigate that if a spring in my valve train that was installed upside-down by some pecker-head, would cause a valve to float. The reality is that the heavier mass of the spring in our valve cavities is suppose to be installed on the valve spring seat, not the retainer side with the cotters. In other words, the more condensed pitch of the spring is installed closer to the central mass of the motor; therefore creating mass centralization, which every manufacturer tries to strive for. If the heavier mass were topside also coupled with spring resonance, it is likely the valve would float or walk.

I was told by an engineer, that there were several instances where upside-down springs were found in our bikes valve trains with no issues, and it further discouraged me because I thought that the only part that was wrong in our manuals about the valves was the lapping part because of the newer hardened surface finish on Ti valves. He also suggested that our bikes have tolerances built into the specs that allow for such scenarios where springs may accidentally be installed with the condensed pitch facing the wrong way.

Since that was evident and impossible to prove or disprove about whether upside-down springs could cause a catastrophic failure, I decided to have not only the free length test done on the one improperly installed spring out of the five valve train; but also the rate of compression test where the length measurement is taken when a certain weight is applied on the spring. This other test that is outlined in the manual, also gives one the numbers they need to know in order to determine whether or not inadequate seat pressure is going to be an issue or not.

Low and behold, the springs' free length (the one I had my suspicions about [because it was installed upside-down] that caused thousands of dollars worth of headaches) was perfectly within free length specs; but, the rate of compression length with a certain amount of weight on it was out of specs by a mile compared to the other exhaust spring in the rebuild I had the shop do. This led me to believe that what 2grimjim was saying about professional engine builders reusing springs that are old being a common practice, so long as the bad springs are weeded out before re-installation; might just very well be true. Which further infuriates me to no ends, because I specifically asked that pecker-head to install the new ones I bought; of which I know, four were new and somehow he got the old and new spring mixed up for the final spring install which just so happened to be conveniently installed upside-down also.

I agree with what is stated in your post, and it essentially comes down to fatigue failure. But man O' man, when I found out that a springs fatigue failure rate is higher, especially when you have a more condensed pitch side to deal with instead of just a plain uniform spring - I wish that he would have installed the new spring in the upside-down orientation just so that I could have a more valid argument against him. Four springs had the bright paint markings on them; but, the one in question had a dull tint schematic paint flash on it, suggesting that it was a reused spring. The failure occurred within 1.2 hours of the shops rebuild. Also, I don't recollect a paint scheme being evident on OEM exhaust valve springs and it further puts up yet another flag in my mind. I thought OEM intake springs have green on the ends and the OEM exhausts springs have no paint scheme????? Something is definitely up with that also, and I'm not in the mood to play the "catch up with colors" game :bonk:

He is a certified professional engine builder and I can't question his choice to reuse a spring (but I should have); but, you can believe I was on his case about installing it upside-down. That added to the valve failure (no doubt) in my mind; but, since he is the one with a plaque on his wall, I'm wrong.

All I know, is that I have a bike with close to 50 hours on it from my own hands (rebuilt from the ground up) and I didn't get paid or have a plaque to justify bad calls when it comes to motor internals.

When the customer pays and asks for something specific (professional engine builder or not) the professional engine builder should be "All Ears" and at least notify the customer when he is going to make a personal choice on the rebuild and from his experience, offer the customer a choice to agree or go against his advice. That way, at least he can partially blame the customer for not heeding his advice - :smirk: .

Edited by nokickstandsallowed

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To the OP. Glad you got it sorted out.

As for valve spring replacement. The professional engine builder I know always installs new valve springs unless the engine has less than 30 hours on it and that too is dependant on what cams are being used. I personally replace the valve springs every time I take the valves out which is usually every 80-100 hrs. I dont care if the springs are in spec. I have seen older springs that were in spec get put back in only to float halfway through the service life of the valves. $30-$50 is cheap insurance when the alternative is floating a valve into the piston and grenading the whole engine to the tune of $1000.00 or more in repairs. Just my .02

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I haven't disassembled my valvetrain yet, but I did pop a bucket off just for grins. I'm pretty sure it was an exhaust one and the spring under it had pink paint. I'll have to check tomorrow to be sure.

If the engine blew up after only 1.2 hours, I'm not sure I'd blame it on an old spring. If that was the case you would have been dangerously close to failure before the rebuild. I also have a feeling a spring that close to failure would be obviously outside of specifications and not put back it... but how would an old one get in there anyway if you got 5 new ones???

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I haven't disassembled my valvetrain yet, but I did pop a bucket off just for grins. I'm pretty sure it was an exhaust one and the spring under it had pink paint. I'll have to check tomorrow to be sure.

If the engine blew up after only 1.2 hours, I'm not sure I'd blame it on an old spring. If that was the case you would have been dangerously close to failure before the rebuild. I also have a feeling a spring that close to failure would be obviously outside of specifications and not put back it... but how would an old one get in there anyway if you got 5 new ones???

There were several factors that caused the failure, and the spring was one of them in a string of events along with a NEW cam chain that displayed crushed in sides on three of the links. It is all documented in my rebuild thread for clarification; but, when I revisited the thread, the cam chain picture was missing the last time I looked. That possibly has something to do with the site upgrade I guess, because the pictures are still in the same photo album that they have always been in since that thread started. Maybe the pictures will return when the site is fully converted over. The cam chain displayed signs of being crushed from the sides without damage occurring to the inside cavity walls or guides and was just perplexing in itself to me. It caused three links to become very restrictive.

As to your final question, I have but one answer: I should have done it myself from the beginning. You do realize that I stated I had the motor worked on by a shop right? The seat not being cut concentric to the valve guide is another possibility I was looking at; but again, from the extent of damage to the head after the failure, it was neigh impossible to prove. The cam chain and the spring were the only two pieces I had left to forensically work with to come up with some possible explanation without dumping tons of money into a metallurgist specialist, because I was broke after the failure occurred and it took several months to get her up and running again. The exhaust valve snapped cleanly off in such a way as to suggest fusion weld failure on the two piece Ti valve design. I am seriously considering the higher priced one piece valves, and possibly the dimpled design valves if they are available as a one piece design for my next valve train upgrade.

Refer here: http://www.thumperta...t/page__st__100

It appears even I was incorrect about the color scheme for OEM exhaust springs (Hint: I haven't been inside the motor for a while because I haven't had a failure :smirk:) - they have green on the ends because I can see it clearly in the pictures of my head because the buckets aren't on them yet. There are two pictures there, that clearly show green paint on the two exhaust springs and even a reflective hue of green on one of the lifter cavity walls.

Edited by nokickstandsallowed

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Looks like I was wrong, too! I just checked and it looks like my exhaust ones are green and intake aren't pink, but kind of yellow ish... I don't know what I was thinking :smirk:

I'm pretty sure Jesse Williams will do dimpling for OEM valves, and he also sells dimpled one piece Ti ones for like $99 each. That's the best price I've seen on one piece Ti ones, AND they're dimpled.

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I emailed Jesse and he will dimple your existing valves no problem. I think he quoted $30 each.

That's a fair price; although, I am at a loss for seeing what the advantage is of having existing two piece fusion welded valves dimpled. I know by design, that they (dimpled valves) are characteristically a better alternative and perhaps a little more attention is required to keep them healthy as far as carbon build-up; but I would want that on a one piece valve, not fusion weld generation stock valves.

I have to tell you honestly, despite the mishap I had with parts, it really is phenomenal how long parts last in our single piston bikes at their revolution speeds on the crank. Further intriguing, is the fact that the engineers are given cost guidelines to make the parts work in relation to mass production time lines and budgets for the general population. That right there, really says something about the commitment on Yamaha's part. They never really leave their customers in the dark without answers or at least fix the issue like they did in '06. There are a lot of motorcycle manufactures that would of just said: "Oh well, your past your 30 day warranty - you were on the limiter too much - take a hike - well, you get the idea.

Yamaha fixed issues well beyond the "Call of Duty" as far as I see it, and I will continue to buy and ride their machines any day - I have all my life, and like their bikes better than any of the others I have ridden to this day. I miss my YZ 60, 80, 125 and IT 175; but, to this day, my 250F would be the most difficult to part with, because I actually slept down in the basement with it for my whole rebuild :smirk: .

Heck, you know me Swede, I hate ACCT's, exhaust junctions and valve trains; but, what am I going to do - ride without those parts? :bonk:

Edited by nokickstandsallowed

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