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powers450f

06 yz450f valve clearance readings?

8 posts in this topic

I just bought an 06 yz450f and I checked the valve clearances and the manual says they should be .10 - .15 mm on intake and .20 - .25mm on exhaust side. the readings I get are .10 on two out of the three intake valves and the middle one I can only get a .08mm feeler in. The exhaust side is reading .18mm on both. Is this just because it has been sitting for a while? The previous owner said he would check them every 20 hours or so and had never needed to adjust them. Which I know is common on the yz450's. My question is don't the clearances get bigger as the valves wear? Is it something I should be concerned about or should I just ride it? It runs good...

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My question is don't the clearances get bigger as the valves wear? Is it something I should be concerned about or should I just ride it? It runs good...
Nope. They get smaller. The valve move up toward the cam as it closes, yes? Then when the seat or valve face wears, it moves up farther, and the clearance is smaller.

Yes it is something to be concerned about. You need to adjust the 3 valves that are below specs, and then keep an eye on them for a while. Check the clearances every ride or two to determine if they are staying where you set them or they are steadily and quickly tightening. If they tighten more soon after you set them, you need new valves.

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Hi, powers450f!

I just recently went through what you're going through, more or less. While changing a cam chain (motor had 60 hrs. at that time), I decided to check the valve clearances at that time. All my valves were at the "lower limit" of the tolerance zone, but more or less in spec.

I had some questions that got answered in this thread (please click here)....

One thing that came up (for me, anyway...) is how hard it is to duplicate the torque on the cam caps that they do at the factory.....

Now, before I did my cam chain, I "SEARCHed" as much as I could here, and read all I could about the job. I read, & re-read my manual. Per Grayracer513's recommendations, I torqued my cam caps to about 75 in./lbs.. I went up in 3 increments, using the tightening sequence in the manual. I checked my valve clearances again (no shim changes) after replacing the cam chain, and they all got about .0005" tighter! :p:lol::bonk:

One thing I didn't like was using my beam-type 3/8" drive torque wrench for this job. It's accurate, but honestly, my old eyes have a tough time reading the small radial increments on the scale. I also couldn't get it & my socket to physically fit between the head & frame for a couple of the cam cap bolts. :ride: So, I bought a CDI brand (owned by Snap-On) 1/4" drive micrometer clicker type torque wrench, checked it at the Calibration-Certification Dept. at work, and used it this past weekend...

I got all my shims I felt I needed, and "re-shimmed" my clearances this past weeekend. I ordered some Honda shims from here at the TT store, because you can get them in slightly smaller thickness increments than you can get the Yamaha shims. I first lightly tightened my cam caps down with with my thumbwheel ratchet, and checked my clearances. An .005" feeler gauge would go (on the intake side), and an .009" feeler went on the exhaust side. But even with taking what I felt were all the precautions I could, my clearances again tightened up a little. Now, an .004" feeeler goes in easily, but not an .005", on the intake side. On the exhaust, it was similar: an .008" gauge goes easily, but my .009" won't. I know I'm not overtightening these things, but that was my experience...... :thumbsup:

Anyway, I hope this helps ya some!

Jimmie

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I checked my valve clearances again (no shim changes) after replacing the cam chain, and they all got about .0005" tighter!

If you use assembly lube on the cams and such instead of engine oil, that can account for the half thousandth.

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If you use assembly lube on the cams and such instead of engine oil, that can account for the half thousandth.

Hmmmm. Not to hijack powers450f's thread, I'll bet you're right. When I did the cam chain, I used some STP Oil Treatment I had for my assembly lube. I know you're somewhat biased against the STP, but it's worked fine for me for years :thumbsup: And I had the valve lash tighten up bout a half a thousandth after final torquing the cam caps......

I found some Clevite assembly lube (Sorry Gray, but it simply looks & feels like red colored STP to me, hee hee :ride:) at an auto parts store, and used that this past weekend. Same results. The clearances tightened up an average of .0005". :bonk: But I see where the oil could account for some tightening. Again, what bewilders me is that I spun the engine over by hand a few times after finish torquing, sorta hoping to minimize that very effect........

Oh well.... It worked out well, and like the original poster, I'll check the lash again in 6-8 hrs. or so.

Jimmie

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So I shimmed all the valves and the intake side is looking good. The exhaust side is right at .20 I mean I can barely squeeze it in. I shimmed them down 2 sizes because they were at .15 should I go down yet one more size or should I leave it alone?? I don't want to big of a gap right?? Thinking maybe the oil is making it bit more tight? Another question your suppose to torque the cam caps to 7.2 ft pounds that seems like not very much at all?? My torque wrench clicks right away?? And one last question I am down to a 1.80 shim is this getting close to needing a valve job, and if so how much on average does it cost?

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If you shimmed them down two sizes, you probably need new valves right now. "Barely squeezing in" the feeler gauge means that it has less clearance than that, and that you are engaged in wishful thinking. Shim them one size smaller and watch them very closely. If they get tighter again in a ride or two, change them before they break.

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Oh great I hope this thing doesn't need a valve job...Gonna be a while before I can afford a thousand dollar valve job. Is it possible the person that owned it prior to me didn't adjust the valves properly?

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