finicky-ness of valve position during clearance check?

[Rema1000]

First weird thing: my Haynes manual says to line-up the "R.T" mark on the left pickup alignment mark. My crank has a "VHR" at 10 o'clock, and a "T |"  at about 2 o'clock, aligned with the RIGHT pickup, when the cam gear cutouts are facing each other (right intake lobe pointing back, right exhaust forwards, left intake up, left exhaust down).  I think I got the valve positions correct for the first clearance check, but it looks like my crank timing marks are 180 degrees off.  My pickup at 8 o'clock has a line next to it, but that doesn't match the cam cutouts pointing either together or apart.

The right exhaust (pointed forwards) will fit my .038mm guage, but the right intake (pointed backwards) will not.  The left intake (pointed up) will fit the .038mm guage, but when I rotate the crank 360 deg., the left exhaust (now pointed up) will not .

Here's where the finicky-ness comes-in: if I only rotate the crank 350 degrees, so that the cam cutouts are not *quite* pointing away from each other, then I can fit my 0.038mm guage under the left exhaust.  But when the cutouts are pointing exactly apart, then the guage doesn't fit.    Similarly, the right intake will not fit the guage when pointed backwards, but it will when pointed up (although that is not a standard position for measurement).  It seems like with the cam pointed at the sky, there is more clearance than with the cam pointed backwards.  And if that is the case, then why am I checking the left intake when it is pointed at the sky, but checking the right intake when it is pointing backwards?

[Diderich]

Yep, same thing on mine.  I ended up checking each clearance in 4 or 6 different position and took some kind of mental average.  As long as the minimum clearance is bigger than ahhh ummm...the minimum listed clearance and it is mostly inside the upper clearance it should be fine right?  This was the opinion at least of me and my father in law.  No problem after 6500 miles at least, for whatever that is worth.

[Kerry]

Check out Srinath's post about checking valve clearances in the old thread Luggage, Racks and Engine Guards from Riderhaus.

I know it seems a bit non sequitur, but it isn't.

[Rema1000]

I agree with Srinath, that the timing mark seems useless.

It sounds like Srinath checks each valve with its lobe straight-up checking to see if the bucket binds under the back-side of the cam lobe.  It sounds like GSJack also checks his by turning the bucket with his finger, but no mention of whether he checks each valve straight-up, or otherwise.

My Haynes manual clearly instructs to check all but the left exhaust at a single point where (on my bike) the left intake is pointing straight up, but the right intake is pointing back (horizontal); and the right exhaust is pointing forward (horizontal).  Then, the engine is rotated and the left exhaust is checked pointing straight up.  Anybody know if Clymer says the same thing?

But I have found that in general, there is more clearance on any valve with the lobe pointing up than pointing either forward or back (horizontal).  And... the point of largest clearance on the left intake/exahaust is found just before the cam notches/cutouts are directly facing, or directly opposite (right side is impossible to call, since the cam notches are pointing up/down).

On two of my valves, there is a point, where the .038mm shim fits.  This tells me that if I use a smaller shim to add 0.05mm of clearance, then these two valves will have at-least one spot where they are out of spec (> 0.08mm).  At the same time, with the current shims, there is at-least one spot where the clearance is less than 0.038mm, and is possibly out of spec.

Right now, I am thinking that I will invite a friend over to help turn the crank, while I spin the bucket by-hand (as Srinath and GSJack suggest).  If there is binding at any point in the loose 3/4 of the cam rotatiotn, then I'll swap shims.  However, it sounds like GSJack and Srinath use clearances less than 0.03mm without problesms, so I suspect that I'll find that I'm OK with what I have (right about 0.03mm), and have no actual binding.

FWIW, I have about 20K on what are probably the original shims (the previous owner only changed oil).  The first real trouble could occur between 16k (JohnLA, the bain of unsuspecting motorcycle valvetrains everywhere) and 40k (GSJack).

[Bob Broussard]

Just rotate the motor, so the cam lobe is pointing straight up (away from the valve. Ignore the timing marks or slots. Do each valve individually.
Put the correct size feeler gauge in and out and feel the way it moves.
If it slides freely, try the next size up. If that size won't slide in, you're fine. If the larger gauge fits, then it's loose (if it's larger than specs)
If you can't get the correct size gauge to fit in, it's too tight.
You can rotate the cam a bit (we're talkin a little bit) to see if the gauge fits. If it will fit at any point at all, you're fine.

[The Buddha]

Right now, I am thinking that I will invite a friend over to help turn the crank, while I spin the bucket by-hand (as Srinath and GSJack suggest).  If there is binding at any point in the loose 3/4 of the cam rotatiotn, then I'll swap shims.  However, it sounds like GSJack and Srinath use clearances less than 0.03mm without problesms, so I suspect that I'll find that I'm OK with what I have (right about 0.03mm), and have no actual binding.

OK that sounds like a good way to lose a finger... Rotate the bucket with the cams not being turned... The shims should be free to spin with the cam lobe horizontal too.
Cool.
Srinath.

[Lars]

If you pull the sparkplugs out you can rotate the crank with 1 hand. With the other you can feel if the shims are moving freely. I can't recall the problem as described here. Just turn the crank until the 2 slots on the cams are towards each other, measure clearance. Then turn crank 180 or 360 degrees ( don't know anymore) and measure the left intake & exhaust. as far as I can recall, the lobes where always horizontal when I did that. That's also a tighter point than with the lobes pointing upwards.

[Rema1000]

as far as I can recall, the lobes where always horizontal when I did that. That's also a tighter point than with the lobes pointing upwards.

Thanks, that makes more sense than the Haynes manual instructions.  Some people say to measure with lobes up, but I think that you really want to see where it is tightest, which does seem to be with horizontal lobes.

Anyways, I retested, and definitely can't fit the 0.038mm feeler on two of the valves; but I also checked all valves with the lobe up, and lobe forward and back, and the shim & bucket can spin freely in all three positions.  So I'm going to let those two valves go for a while.  I really didn't want to change shims today anyways.  This was my first "tank-off" experience, and I wanted it to be a pleasant one.