Checking valve clearances with the head off?

My 750-4 head is off right now for an upper rebuild. Is there any reason why I can't install the valve assemblies, buckets, shims, and cams with the head off and check my valve clearances? I can't see any difference with turning the cams be hand instead of the cam chain.

And should the noses of the lobes be 180 degrees away from the buckets when doing measurements?

Finally, is there a problem with swapping the shims around to bring clearances closer to stock? Thanks!

Your questions are pretty easy to answer.
Yes. Remember ONE cam at a time
Yes.
No problem.Cuts down on $$ shim inventory required.

If I can do it you can. Get a good manual, good luck.

I'm not sure of the procedure for a 750 but I don't think that it would be a problem. The FSM for a 1000 says to line up the marks on the intake cam sprocket with the valve cover and measure the two that have clearance, then turn the crank 1 turn which results in half a turn on the on the cam and repeat for the other two valves. Then do the same on the exhaust side.

As for swapping the shims...Swap away! The one time you won't get in trouble for swapping!:laugh:

You can use a large flat screw driver to rotate the cams.
Place a piece of towel down on the front or rear edge of the head, then you can wedge the driver in the cam gear and pry the cam gear upward a notch at a time.
Towel preventing damage to gasket surface of course.

GL

Polcat, I always do a "bench adjust", simply because it's so much more "comfortable'. BUT.. I also find that upon assy typically 1 or 2 clearances have shifted. re-check... 2nd, simple lobe away measurements vary. the base circle on cams can vary.. while some manuals rec. checking clearances for multiple valves/cyls at single crank positions, I check/set 1 cyl at a time. per cyl at TDC. and set to the loose side of spec. cleanliness is important!!! once you think your' done, rotate crank a half dozen times & re-check. luck

I agree with gane. I do a bench adjust first, then double check after torqueing the head down. Inevitably a couple will change with the tightening down. They are a pain to do on a 750-4, but with a little practice I was knockin it out pretty easy. The trick is to measure all of them at once, write them down, and adjust them all at once. That way you only have to take the cams loose once, hopefully. I also found that using a paint marker to dot the cam and chain makes lining them back up a snap. Just keep tension on the crank end of the chain so it can't slip there.

my .02

There can be slight variances in clearance from "no chain" to "chain installed and torqued down". It's because the camshaft has some up/down play and the chain will keep the cam pulled down tight to the journals as compared to no chain on it. I have a couple of valves where the change is about .001" to .002" because of the "chain pull" effect. I see the same variance if I reverse rotation and release chain tension when measuring.

bountyhunter, let me see if I follow you. The clearance between the cam bearing journals and the bearing area is compressed downward by the chain tension, slightly changing the readings?

My manual says that cam to bearing clearance should be about .19mm, half of which should be about .095mm clearance all around the cam when it is spinning in a bed of oil, which will, of course, hydroplane it off the bearing surfaces.

So, if I torque the cams in and then push down on it while taking the readings, seems I should be able to get pretty close. Even if the cam did shift downward from chain tension, which I wouldn't have with the head uninstalled, seems that I'd get ever so slightly more clearance then wanted, which is better then slightly less.

Another advantage of bench shimming is that you can use a pair of quick grips to press the cams down while you install the cam caps - this takes a lot of stress off the cam cap bolt threads and minimizes the risk of stripping a thread.

As shown in the pic I also like to set the head on a couple of wooden blocks to raise it from the workbench - as you rotate the cam the valves will poke out beneath the head, if the head is flat on the workbench you risk bending a valve (might not happen, but better safe than sorry).

I find the easiest way to rotate the cam is to mount a cam sprocket bolt in the cam and use a 10 mm wrench.

polkat wrote:

bountyhunter, let me see if I follow you. The clearance between the cam bearing journals and the bearing area is compressed downward by the chain tension, slightly changing the readings?

My manual says that cam to bearing clearance should be about .19mm, half of which should be about .095mm clearance all around the cam when it is spinning in a bed of oil, which will, of course, hydroplane it off the bearing surfaces.

So, if I torque the cams in and then push down on it while taking the readings, seems I should be able to get pretty close. Even if the cam did shift downward from chain tension, which I wouldn't have with the head uninstalled, seems that I'd get ever so slightly more clearance then wanted, which is better then slightly less.

I have bench shimmed a head on my 650. I checked it after I installed it and ran the engine for for a short ride down the street and found the identical clearences as I did on the bench. I wouldn't worry too much about dynamic oil film or can chain force, you will be just fine shiming it properly off the engine. sincew I had ground the valves and setas I set the clearences up near the top end and tried to get them all within a thousandth. That gives me some room as the valves fin thier new home in the seats.

Just my 2 cents.

polkat wrote:

bountyhunter, let me see if I follow you. The clearance between the cam bearing journals and the bearing area is compressed downward by the chain tension, slightly changing the readings?

Does on mine, I have two shims that will change about .002 by releasing chain tension. I checked cam journal clearance and they are in spec.

polkat wrote:

So, if I torque the cams in and then push down on it while taking the readings, seems I should be able to get pretty close. Even if the cam did shift downward from chain tension, which I wouldn't have with the head uninstalled, seems that I'd get ever so slightly more clearance then wanted, which is better then slightly less.

I think you want spec clearance with the thing installed and torqued down, and chain pulling down the cam which will close down the clearance a bit compared to "no chain" reading.

I remember a shop in San Francisco, KC Engineering I think, where the owner was a KZ nut and he did a great job of bench shimming. He used an old KZ cam that was cut in half so he could bolt it in and check clearances without having to compress the valve springs on the open valves. I am about to do the same with the old cams that came out of my KZ as I won't be needing them anymore...