Topic: Vexing Valve Adjustment

[Paul E.]

I've been working through the Clymer "Periodic Maintenance and Tune Up" section and hit a snag when I got to the valve adjustment section.

So the image in the manual for checking the valve clearances looks like this:


I need to measure the clearance between the adjusting screw tip and the top of the valve stem.  Buuuuut my valves all look like this:


WHOA!  That's not 2 thou that's more like a 1/4" !!!

So I thought, well maybe the screw just needs to be advanced.  So I advanced them like so:

And at this point realized that it doesn't seem like I'm ever going to get the bottom of the rocker arm to touch the top of the valve.  As I turn the adjustment screw and advance the rocker arm down it seems like it is going to get to the top of the valve, but then the adjuster screw comes all the way loose.  What's going on here?  Are my valves some how a 1/4" lower than what they should be, or am I misunderstanding where the measurement should be taken from. 

If I had to guess, maybe the measurement is supposed to be taken from the BOTTOM of the adjuster screw to the top of the valve stem.  In that case I need to get some feeler gauges with a 90 degree turn in 'em to get them to fit.  Here's a picture showing what I'm "hypothesizing" about:


OH YEAH!  One more thing.  To determine which cylinder is at TDC the manual says the cylinder that has both its rocker arms loose is the correct one.  Neither my No. 1 nor No. 4 had loose rocker arms when I had the T 1-4 mark aligned in the peephole.  Maybe this has something to do with the rocker arms being 1/4" too high??? 

[flybox1]

"If I had to guess, maybe the measurement is supposed to be taken from the BOTTOM of the adjuster screw to the top of the valve stem.  In that case I need to get some feeler gauges with a 90 degree turn in 'em to get them to fit.  Here's a picture showing what I'm "hypothesizing" about:"

EXACTLY.  or just bend the one you have.

"OH YEAH!  One more thing.  To determine which cylinder is at TDC the manual says the cylinder that has both its rocker arms loose is the correct one.  Neither my No. 1 nor No. 4 had loose rocker arms when I had the T 1-4 mark aligned in the peephole"

I dont know where you got 1/4" because in pic 2 it looks as it should, just get your feeler gauge in there.
the rocker arms movement is so slight.  you can miss it if you are ham-handed.  pic 3 - DOH...put your lock nut back on.  now, grab the lock nut and lift up and down...you'll feel the slight tap.  if you dont, you'll have to turn the BIG NUT to T 2/3 and start with the intake/exhaust of #4 checking for TDC and loose rocker arms on intake and exhaust of #4, set those per the manual, then go 'round to T1/4 and do those starting with intake and exhaust of #1.

[flopshot]

determine where each is at it's "most loose" position and adjust accordingly.  it ain't rocker science.   rule of thumb,  when one rocker is 3/4 of the way down the other valve should be closed.  unless of course you have the camshaft from hell.

[Ernest T]

Most bike shops will sell a feeler gauge with a 90 degee bend or you can just bend your regular gauge.

[seanbarney41]

+1 on bending your feeler gauge but be careful as those thin ones can snap easily

[NewOldSchool]

Another tip to make sure the valves on cylinder 1 are both closed when the timing mark is at the "T" for 1-4 is to turn the motor over while watching the rockers on cylinder 1 open and close.

Turn the motor over one complete revolution while watching for the rockers to move up and down

Once you see the intake go down then come back up, and the exhaust go down then come back up check that you are aligned with the "T" for the timing marks 1-4.

Grab the rockers at cylinder 1 with two fingers and wiggle them up and down, they should move VERY SLIGHTLY and if you listen you will hear "tick, tick, tick" as they touch the top of the valve. Those valves are closed and able to be adjusted.

Open valves will be rock solid and not move up and down because of the spring pressure.

Now follow your manual and adjust the others accordingly.

[dave500]

you need to bo on tdc on the compression stroke,,you also have a tdc on the exhaust stroke,,im guessing thats where you had that cylinder so backed of that valve wrongly?i just cut a feeler off square then on a stone sharpen the burr off both sides and itll slide in easy.

[Trevor from Warragul]

"NewOldSchool" is right on the money.  The clearance is between the tip of the "screw" and the top of the valve.  When it talks about the rocker arm being "loose", it isn't very loose at all.  When you have the adjustment "right", it should make an ever-so-light tick-tick-tick noise when you play with the rocker.  You'll actually get quite good at knowing when the clearance is correct by the "feel" of the looseness & the sound of the tick-tick-tick!

[Rigid]

It's a four stroke, that piston comes up twice, once on tc compression, and once on tc exhaust.  You want the compression one, see above.