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My bike has a about 4000 miles on it. Never had to adjust the valves, that I have personally checked numerous of times. They've always been spot on. After not doing a check for sometime, I checked them and the exhausts were at.006", oops. I checked them several times, to make sure. I even slept on it and went back out the next day and did it again.

Okay. I order a full set of shims, mic the originals, and shim it to spec. I went out riding a couple of times. The bike seemed a little sluggish, but I figured that was because I'd been riding my CR500 for a couple of months.

Decided to recheck the valves to make sure they weren't retightening. Whoa!! Was I surprised to find they were at .017"-.018". Way too loose.

I put the original shims back in. Gap is at .010-.011" - perfect. Bike runs a whole lot better. Any ideas how this could possibly happen?

Don't. I know what you're thinking:-)

Obviously, the measurment at .006 was wrong. I just can't figure out how I could have gotten that figure, when I checked, double checked, and triple checked it. The good news is, for all those worried about 450X valves, don't. 4000 miles and never budged.

Was the crank/cam in the proper position when you checked the clearance @.006?

Either that or he had some feeler guages stuck together........hey, it happens.

Slow Joe wrote:Was the crank/cam in the proper position when you checked the clearance @.006?

this is VERY common and easy to do. one way to make sure this doesn't happen is use the ignition timing mark ALSO.

ken

Slow Joe wrote:Was the crank/cam in the proper position when you checked the clearance @.006?

Having checked it quite a few times, I'm reasonably sure the crank was aligned properly. Having said that, I'm not sure how it could have been.

Oh,well.

I guess I was measuring it at TDC of the exhaust stroke, not the compression stroke. I would not have thought there would be .006" clearance on the exhaust stroke TDC. I guess that's what tripped me up. It is kind of odd that I had measured it 6 or 7 other times, and never had that happen.

I guess I was measuring it at TDC of the exhaust stroke, not the compression stroke

That's exactly what happened, and it's easy to do.
Glad your valves are okay.
The other way to check it is just like the manual says-If there is play in the exhaust tappet (like the .010-.011)you're there, if no play,(like the .006) you're 180 out.
I've seen this like 3 times from guys wanting me to shim their valves thinking they were too tight, when in fact they were fine.
It makes me wonder how many times people have shimmed them anyway then did something crazy like start their bike---oops.
Then of course , talk about the "junk" Honda valves Doug

Doug,

Actually, there is noticable movement in the rocker arm when it has .006" clearance. That is why I thought it was on the compression stroke, not the exhaust. I lined up the dot and arrow, wiggled the rocker, and thought I was good. Not!

I did ride the bike after setting the valves way to loose. It did seem a little sluggish. But, because the valves were set too loose, not too tight, there were no interference issues that might do damage. Once I set them back to spec, the bike ran great!

The moral of the story is, if the valves measure tight, rotate the crank 360 degrees and measure again to make sure you're on the compression, not the exhaust stroke.

Actually, there is noticable movement in the rocker arm when it has .006" clearance

That's good to know, and one of the reasons that sites like this are so great, we can save each other untold angst ! Doug

I am surprised that there is clearance when 360 degrees out.

What sort of valve timing figures do 450s have.
Post them anyone I'm curious now.

Perhaps they close the exhaust early for some reason.
I assume from the statement that it was only the exhaust valve at .006 and the inlets were at spec.

I would have thought there would be more overlap to allow for extended rev range in these engines.

Aussiecrf230 wrote:I am surprised that there is clearance when 360 degrees out.

What sort of valve timing figures do 450s have.
Post them anyone I'm curious now.

Perhaps they close the exhaust early for some reason.
I assume from the statement that it was only the exhaust valve at .006 and the inlets were at spec.

I would have thought there would be more overlap to allow for extended rev range in these engines.

Zactly. That's what I would have thought, also. That's why I'm a little confused about the whole thing.

Yes, intakes were fine. I'm going to measure them again today. I'll check them on both strokes and see if I get the same results.

gprodick wrote:

Aussiecrf230 wrote:I am surprised that there is clearance when 360 degrees out.

What sort of valve timing figures do 450s have.
Post them anyone I'm curious now.

Perhaps they close the exhaust early for some reason.
I assume from the statement that it was only the exhaust valve at .006 and the inlets were at spec.

I would have thought there would be more overlap to allow for extended rev range in these engines.

Zactly. That's what I would have thought, also. That's why I'm a little confused about the whole thing.

Yes, intakes were fine. I'm going to measure them again today. I'll check them on both strokes and see if I get the same results.

As long as your cam is rotated so that the bump in the cam doesn't press on the bucket you will measure the same as when at TDC compression (base circle). That allows about 270 degrees of cam rotation that would give you the correct intake valve spec.

Right, A visual inspection will show that there is no lobe contact with the bucket, then you know your on the compression stroke.

Alright, the mystery is solved!!!! You're going to love this.

I checked my clearances again today. When the dimple on the outer portion of the crank gear near the teeth is aligned with the arrow on the case, it is at TDC on either the exhaust or compression stroke. Valves are set on the compression stroke. As I thought would be the case, there is no valve clearance on the exhaust stroke, only on the compression stroke. When the dimple is aligned with the arrow, and you wiggle the rocker arm, if there is some freeplay, you will know you're on the compression cycle.

So how did I get a reading of .006" on the exhausts?

Well, damn, I realized the is another dimple on my crank gear. It is closer to the center of the gear and about 80-90 degrees past the dimple on the outer part of the gear. In my haste, I aligned that dimple with the arrow, reached up and wiggled the rocker. Yup. There's definitely free play, must be TDC on the compression stroke. WRONG!! It was 80 degrees past TDC. Still had a little play. Actually, .006" of free play. Today, I measured again at the second dimple and sure enough it was .006"+/-. Man, I couldnt' believe it. I bought $80 worth of shims for nothing.

It was a crazy mistake, but one that I'm sure others might make, if they are not paying attention. The good news is, I'm tickled pink that my valve clearances have not changed in roughly 4000 hard miles.

End of story.

Nice job, I've wondered why in the world they put that other dimple in there at all.
This has to be in double figures now as far as how many times I've either personally seen a bike where the owner was sure it needed shimmed or heard of an example.
Imagine what happens when then they go ahead and shim the valves ! What happens then is the myth of Honda having "junk" or fragile valves grows, because then they're good and screwed up.
I shudder when I read of a new guy talking about needing to shim his valves because on his new bike some of them are "way off". Maybe one and maybe a little.
One red light should be is the bike starting and running great but supposedly with these way out of whack valve clearances,the two don't go together,
Good work GPR. Bet you got an endorphin rush off that one, coming back from the garage, clearly "the man" ! Doug