Shimming valves on 07 yz450f?

[tom n]

Hi, thanks for looking. This is a continuation of sorts of a recent cam chain replacement thread I posted a few weeks ago and since that went so well I tried to do all the homework I could before posting this thread as to make it as easily answered by you folks as I could. Here goes. 07 yz450f, 60 hrs.

All specs in mm's. Exhaust valves- both measure same clearence each: .1905mm's. Intake valves- all three same clearence each: .081 mm's...

Now, according to the manual, my tallest allowance on the valves are exhaust: .250mm's, and intake: .15mm's...(1) I'm not sure if this is the desired measurement I should be looking to, but let me know if this isn't right? I'm figuring that shimming to the tallest spec would give me the most time/wear before i have to re-shim or send out the head.

Now, the stock supplied exhaust shims are sized at 1.778mm's. The intakes measured 1.83,1.87 and 1.72 (starting from the chain side). (2) Why aren't any of these shims measuring in half mm's like the manual says?

Anyway, I took those figures and calculated how much they were out of spec, how much clearance was desired, and utilizing the existing shims I ended up with needing the exhausts: 1.718mm's, and intakes: 1.75, 1.80, and 1.65mm's. Now the intakes i'm happy with (if my desired calculations are correct), but my exhaust's shims are not so easy to figure because (3) Do I go with 1.70's which puts me taller than the tallest spec the manual gives (which is .250 max clearance)? Or, do I go with the 1.75's which is well in spec but not enough to match the "room to spare" that the intakes will have? Being honest, I've heard the Honda's shims go in .025 mm steps (instead of Yamaha's .05mm steps) and they fit my Yamaha. If this is true and good thinking, i'll get 1.725mm's for the exhaust to keep all the valves even(ish).

If someone could point out my errors or if you have a better way, please let me know. PS, I phrased my questions with (). Thanks, Tom

[tom n]

nevermind for now:bonk: I screwed up the existing shim sizes and that will only confuse the situation:bonk: GEEZ, i tried so hard.....

[Mr. Neutron]

(1) I'm not sure if this is the desired measurement I should be looking to, but let me know if this isn't right? I'm figuring that shimming to the tallest spec would give me the most time/wear before i have to re-shim or send out the head.

You can do that. Grayracer513 pointed out that you loose a tiny bit of performance, and gain some noise by doing that. But basically, if the clearance is "in" on a valve, it's in, and if it's not, it's not. When I did mine, I strived for the "middle" of the tolerance zone. That's sorta tough to do, and really, since all we can check with is feeler gauges, it's awfully tough to get that sorta precision. With a total tolerance span of only .004" (In EDIT: It's .002"/.05mm total tolerance zone for our valve clearances, not .004"..... ? ), we're pretty lucky to hit within the tolerances, given what what we use to shim with, what we use to measure with, and the variable that torque on the cam caps gives.....

Now, the stock supplied exhaust shims are sized at 1.778mm's. The intakes measured 1.83,1.87 and 1.72 (starting from the chain side). (2) Why aren't any of these shims measuring in half mm's like the manual says?

Because the factory techs that assemble the engines get to use "the Good Stuff" that we don't get, hee hee.... I wondered that same thing when I pulled my cam caps & lifters off, and saw the odd thickness increments. Again, Grayracer513 ("May he Forever ride a Yamaha 450, so He can help keep mine running!" ? ) pointed out to me that the assemblers at the factory get to use thicknesses of shims they don't sell to us..... And he further pointed out that those assemblers set the valve lash to "the lower end" of the tolerance spectrum intentionally. This gives the benefits of a llittle quieter motor, and a *slight* bit of a performance gain, from a little extra lift & duration you get with less clearance (versus what you get with "more" clearance). Hard to say if the average person is gonna notice it though.....?

Anyway, I took those figures and calculated how much they were out of spec, how much clearance was desired, and utilizing the existing shims I ended up with needing the exhausts: 1.718mm's, and intakes: 1.75, 1.80, and 1.65mm's. Now the intakes i'm happy with (if my desired calculations are correct), but my exhaust's shims are not so easy to figure because (3) Do I go with 1.70's which puts me taller than the tallest spec the manual gives (which is .250 max clearance)? Or, do I go with the 1.75's which is well in spec but not enough to match the "room to spare" that the intakes will have? Being honest, I've heard the Honda's shims go in .025 mm steps (instead of Yamaha's .05mm steps) and they fit my Yamaha. If this is true and good thinking, i'll get 1.725mm's for the exhaust to keep all the valves even(ish).

If someone could point out my errors or if you have a better way, please let me know. PS, I phrased my questions with (). Thanks, Tom

Tom, I'll let YOU figure out your valve shims/clearances you want. I will say this: Even though Honda says they sell shims down to the .025mm increments, I ordered some, and got them to the .01mm variety. For example, I ordered 1.725 & 1.775 shim pads, from the TT store here. I got either a 1.72 or 1.73, and a 1.77 or a 1.78, if I'm recalling correctly..... The shims are out in my barn, and I am not able to get out there just now (knee went gunnybags on me.... ), so I'm not 100% certain on the sizes I received & said above here, but I do know for certain they weren't down in size increments as little as I was expecting. Everything still worked out though, and likely will for you as well. Don't lose any sleep over that, and let me know if your shims you get are in .025mm increments, please?

Jimmie

Edited March 24, 2011 by Diesel Goober
Messed up BIG TIME on several important points...

[grayracer513]

Honda sells in .025mm increments, not .005mm. .025mm is .001".

Worrying about where the valves fall in the spec range is a little silly in light of the fact that the whole range is only .002" wide. Set them as close to the minimum as practical, but don't sweat over having one at .10mm and another at .15mm.

[Mr. Neutron]

Grayracer513,

Thanks for catching my errors there! We do indeed have a total tolerance span of .002" (.05mm) rather than the .004" I mentioned earlier. Sorry for that inccuracy. And also, thanks for catching my screw up on Honda's .025mm thickness increments. I shouldn't post when I'm pressured for time, or taking "No Pain" meds for my knee, I guess...... Again, thanks for catching that! I owe ya......

Jimmie

[tom n]

Yeah i was trying to be so CLEAR but as I often do I messed up what I was asking. Sorry about that, I do appreciate the replies to what I was asking. I think I will go ahead and stay midrange in the tolerances. I dont like noises at all. I'm gonna just check the valves more often. I will bring my verniers with me to the Honda shop to make sure!

Its been said that after shimming once, if you need to shim again, the valves are gonna be running thin and it would be unwise to continue to run it. I agree with that however, that statement is a little open ended meaning that one persons shimming process varies from the next based on how much "wear" was done to each machine before that person got it. There has got to be a wear tolerance out there. That way, if I was diligent in recording the wear, I should be able to prevent a failure but still get a full life from the valves. Oh, are the 07's valves titanium? ( i know they cant be lapped) thanks, Tom

[grayracer513]

Y...are the 07's valves titanium? ( i know they cant be lapped) thanks, Tom

All YZF's from 2001 onward use Ti valves.

Any more than .10mm reduction in shim size (.004") is usually a sign of a valve worn to the limit. The absolute giveaway is a valve that won't hold the same clearance it was last set to for more than a ride or two.

[tom n]

Ok, I completed shimming the valves. I ended up going to the Honda dealer to get the shims. I ended up getting what I thought I needed but as it turns out, you guessed it, what was stamped on the shim differed from what the true thickness was. So I bought what was close and left it at that. One of the intakes and one of the exhaust was in good specs. The other two intakes and one exhaust left me just shy of not being thick enough. But they all are .0035" to .004" less than where they were from when I started. I hope this is ok, if theres some concern, please let me know! (it seems to run/sound fine!)

Which brings me to another question. Is it that big of a deal if you put in shims that are a little too thin? If I am thinking this right, all that would do is bring on the cams a little later (as well as leave them earlier) and also limit the lift. But what I dont see is what the real disadvantage is besides a very little loss in performance? Shoot, even the valve springs aren't compressed as much. OK, now I know i'm stretching it a little. But can someone set me straight on this a little more?

I'm not sure how much longer I should go with the stock piston, I was first thinking of changing that when sending out the head but now i'm not so sure I should wait that long, 60 hrs. seems to be long enough for a stock piston, what do you folks think? Many thanks to all..... Tom

[brentn]

Any shim kits that you can buy out there that have stamped thicknesses that are 100% true?

[Mr. Neutron]

Brent,

Going on the little, limited experience I have with these shims, I'd bet there aren't many that are 100% what they say they are supposed to be. Those guys tha tmake the shims have manufacturing tolerances just like I do at the machine shop I work at. Out of pride, I'd bet that most machinists would like to hit a "theoretically perfect" size every time, but the reality is that it's hard to do that for that 100% of the time......

But really, the "good news" is that a guy can do pretty good on this valve shimming job with what's available, by being methodical, taking as good of measurements as we can, being careful to torque in sequence, torque up in stages, & etc.... And. Like Grayracer513 says, use the lower torque value than the manual says (somewhere around 75 inch/lbs. ???).

Again, my limited experience showed me that the torquing of our cam caps is very critical for good results. I tried using my 3/8" drive beam type torque wrench the first time I did my valve lash. It had interference probs with the socket I had to use; didn't fit well between the top of the motor & the frame. That, & I was having a tough time being 'consistent" with my torque readings...... Basically, I've become so "dependant" on the micrometer click-type, I didn't feel good about my results with my old reliable Craftsman beam type.... ? The clearance issue was a non-issue after I bought my CDI 1/4" drive clicker/micro adjust torque wrench, and I think I got more consistent results with it..... Just my own experience here......

Jimmie

[grayracer513]

The important thing is not the shim thickness, it's the resulting valve clearance. Having an excess of clearance is hard on valve train components because it increases the amount of impact the components deliver to each other as the valves are opened. It's also noisier. Too little, and you have compression sealing problems and cause damage to the valve faces.

OEM Yamaha shims are stamped correctly as to their size insofar as I have ever found, and most of the so called errors in the shim markings are actually errors in reading/using micrometers, incorrectly zeroed micrometers, or attempting to use vernier calipers to measure them.

[Mr. Neutron]

most of the so called errors in the shim markings are actually errors in reading/using micrometers, incorrectly zeroed micrometers, or attempting to use vernier calipers to measure them.

Good Point!!! And also, the measuring we do with feeler gauges to check our clearances isn't exactly the most accurate way to measure either, as you've pointed out before......

Jimmie

[tom n]

OK I went back in to the valve cover to double check the clearances as well as the torque on the bolts. All were in spec. except the right hand intake (closest to the kickstarter). That one measured .007. Is this OK? Also, I torqued the bolts to 75 inch lbs. Let me know if anything is incorrect as I still have it apart. Thanks guys, Tom

[grayracer513]

.007"? No, it's not OK. The spec is .004-.006". Why even ask?

[tom n]

"Ok dad, you dont have to yell at me......man...." But seriously, i wanted to make sure that the manual was correct on this point since, well, its wrong on some others eg. Torque specs, shimming in general and a few others you have addressed in previous posts. I guess I was just trying to excuse my poor machinist abilities. I'll make it right and post it when its done. Thanks again to all who took the time to post. Couldn't have done it without you. Tom

[tom n]

Ok guys, its all done. She starts and runs just fine! Im heading out to Apex tomorrow to kill the dunes. thanks again to all Tom