Quick question about measuring valve clearances

[teh_engr]

Hi Everyone,

I have a quick question about measuring valve clearances (my first time). It seems to me that I can get varying valve clearances by rotating the engine slightly (maybe 15 degrees) from the specified positions in BikeClliff’s guide. For example, my cylinder 4 intake measurement is <.0015” at 12:00 and .002” at 12:30. Because it’s hard to say what exactly is parallel/perpendicular to the gasket surface, this makes me question my measurement accuracy.

I verified that the cam shaft bearing caps were torqued to the minimum specified torque value or greater (they could be overtorqued?), and I've turned over the engine manually a couple of times to make sure things should be seated. Also, to be clear on my technique, positions are as follows:

1. To measure 1 & 2 exhaust, point #1 exhaust cam lobe forward/parallel to gasket surface
2. To measure 3 & 4 exhaust, point #4 exhaust cam lobe forward/parallel to gasket surface
3. To measure 1 & 2 intake, point #1 intake cam lobe upward/perpendicular to gasket surface
4. To measure 3 & 4 intake, point #4 intake cam lobe upward/perpendicular to gasket surface

This ensures that neither of the two valves are depressed when measuring, which I understand to be the goal of this technique.

Does this suggest mechanical problems with the bike, bad technique, anything else? Am I overthinking this?

Thanks,
Jack

[chef1366]

Hi Everyone,

I have a quick question about measuring valve clearances (my first time). It seems to me that I can get varying valve clearances by rotating the engine slightly (maybe 15 degrees) from the specified positions in BikeClliff’s guide. For example, my cylinder 4 intake measurement is <.0015” at 12:00 and .002” at 12:30. Because it’s hard to say what exactly is parallel/perpendicular to the gasket surface, this makes me question my measurement accuracy.

I verified that the cam shaft bearing caps were torqued to the minimum specified torque value or greater (they could be overtorqued?), and I've turned over the engine manually a couple of times to make sure things should be seated. Also, to be clear on my technique, positions are as follows:

1. To measure 1 & 2 exhaust, point #1 exhaust cam lobe forward/parallel to gasket surface
2. To measure 3 & 4 exhaust, point #4 exhaust cam lobe forward/parallel to gasket surface
3. To measure 1 & 2 intake, point #1 intake cam lobe upward/perpendicular to gasket surface
4. To measure 3 & 4 intake, point #4 intake cam lobe upward/perpendicular to gasket surface

This ensures that neither of the two valves are depressed when measuring, which I understand to be the goal of this technique.

Does this suggest mechanical problems with the bike, bad technique, anything else? Am I overthinking this?

Thanks,
Jack

I do each one seperately by pointing the cam lobe directly opposite from the shim bucket or tappet.

[BassCliff]

Hi Mr. teh_engr,

The procedure you outline is right out of the Suzuki Shop Manual. I don't think you can go wrong doing it by the book. And I like using millimeters (.03-.08mm) instead of inches (.001-.003") since the shims are marked in mm too. It just makes the math easier for mme.

Thank you for your indulgence,

BassCliff

[psyguy]

Because it’s hard to say what exactly is parallel/perpendicular to the gasket surface, this makes me question my measurement accuracy.

if you look at the cams/lobes with your eye level to the gasket surface it's not that difficult to say what's paralel/perpendicular
some cams have a slot on one end that makes it even easier to align with the gasket surface

other than that, yeah, you might be overthinking the issue

some wear on the cam jurnals oposite the cam lobes is possible, especially if the valves were run tight for a while
the cams may have a min runout as well
both would contribute to slightly different readings on the clearances when the lobes are in slightly different positions

[teh_engr]

other than that, yeah, you might be overthinking the issue

I do that a lot- It's a bad habit.

I belive that I'm done with the valve check now, and all tolerances are below .004" (0.10mm). Most are probably less than 3.5mil (0.089mm) with the exception of the cylinder 1 intake valve clearance which is closer to .004" (I can get the 4 mil feeler gauge under the cam lobe on this valve only, but there is very noticeable drag).

Is .004" on an intake valve too loose? I do not have any additional shims of the appropriate size and none are available locally, so I will have to wait an additional week if this is excessive clearance.

Thanks for the advice!!

[psyguy]

the specs are:
0.03 - 0.08 milimeters
a little bigger gap - up to 0.10 mm wont hurt

[teh_engr]

I'll run with what I have now in that case. Thanks for the help.

-Jack

[Steve]

0.004" is technically out of spec, but many of us run it anyway. The alternative is to change the shim and take the clearance to just above the minimum. If you do that, you will likely have to change it at your next service interval, so you may as well leave it there for now.

.