valve clearances, the right way(?)

Ok here's one...

I finally got around to checking the valve clearances on my F1 yesterday (in addition to re-torquing the head nuts) using a Haynes, Clymer and a factory manual for the B1. Clymer says turn the engine until a lobe is pointing directly away from the valve (the tip of the lobe will be at its furthest point from the bucket) but Haynes and the FM say to turn the engine until the EX mark on the cam aligns with the front of the head and check #1 and 3, however this means the lobe is either pointing straight up (#1) or pointing at a similar angle down (#3)and not as the Clymer suggests.

I get different results depending on the method with the Clymer method producing clearances that are too tight (less than .08mm). I lean heavily toward "Clymer is good for pictures only" as I continue to find all kinds of discrepencies in it, but wanted to check what everyone else is doing. Which way is correct?

And while we're here...

Do clearances ever get tighter with age, it seems to me that wear on springs and other material would only widen the gap. What are specs straight from the factory?

Hopefully you are all out riding at the moment.

yes on these bikes the clearances will tighten, I was led to believe it was due to soft valve seats.

I always point the cam lobe away from the bucket, but I have heard of others doing it other ways. I think you will be alright either way.

alexgehrig wrote:

...Clymer says turn the engine until a lobe is pointing directly away from the valve (the tip of the lobe will be at its furthest point from the bucket) but Haynes and the FM say to turn the engine until the EX mark on the cam aligns with the front of the head and check #1 and 3, however this means the lobe is either pointing straight up (#1) or pointing at a similar angle down (#3)and not as the Clymer suggests.

I get different results depending on the method with the Clymer method producing clearances that are too tight (less than .08mm)....

Have used the "Clymer" method as being easy and fast when checking the gaps.

But the objective is for gap to be correct at whatever position the cam allows maximum gap.

Just hand turn crank using the 17mm fake nut under the points cover until the maximum gap is found (regardless of the exact lobe position), and use that maximum gap position to measure the clearance.

The specified clearance is the maximum gap encountered between the lobe and shim (or bucket) as the cam rotates.

Good Luck!

One thing: turn the crankshaft in the same direction as it normally rotates when you check clearances. Reversing direction can cause slight variations due to the camshaft lifting up as the chain slack is released.

My manual says point the cam directly away from the valve. You should not see large variations at other points, if it's more than a couple of thousandths I think there is a problem with the cam.

alexgehrig wrote:

Do clearances ever get tighter with age

Normally, they may tighten very slightly. I have on two occasions seen one widening and I knew what it meant: valve job time. Valve guide oil seals were letting oil seep down through the valve seat opening. Crud was building up on a valve seat and valve so much that the valve no longer seated completely. The valve was gradually being held a couple of thou away from fully seated position.

alexgehrig wrote:

Do clearances ever get tighter with age,

Yes I've heard it because the valve seats get pounded into the aluminum heads.
Mark

Yes, most valves will tighten up with age. I like the lobe pointing straight up to check valves. Your looking for .003-.007, with .005 being a nice mid point. You said F1 right?, that makes it a 1980 650 like mine.

Yessir, though it looks like you have a black engine, is it an F1?

Here's the deal with the variance in lash you run into.

By design, cam base circles are supposed to be perfectly rounded. In reality, they are often not perfect.

In theory, you should be able to check the lash at any point on the base circle of the lobe and get the same measurement. In reality, that often doesn't happen.

Pointing the lobe directly away from the bucket, virtually assures the manufacturer that you have the cam on the base circle. No matter what, you shouldn't do any damage to the motor using that method.

Kawasaki told us many years ago to point the lobe straight away and set the valve at max loose setting.

If you have a camshaft that varies anywhere on the base circle by a significant amount when checking lash, it's either a very worn or very badly ground camshaft. Plain & simple. I've seen some well used, aftermarket cams with very out of concentric base circles, still chugging away and the motors work just fine with them.

When you slip the feeler gauge in there, move it side to side. You'll get a better feel for the true amount of lash.

More lash equal more cranking pressure and more live cylinder pressure. More cylinder pressure means better acceleration.