Because checking the valve clearance on the S40 is such an epic pita, I am mulling over in an unused crevice of my mind whether I could eventually get away with simply rocking the rocker back and forth by hand to decide whether I really need to back them off and start from scratch or whether they feel good enough to leave.

The last few times I've set the valves I've tried to get a feeling of what the right clearance feels like.

Just canvassing opinions on this.

"Checking valve clearance by gut feeling only."

That's like the "butt dyno"  

(every time I wash & polish my bike I swear it runs faster/better)

justin_o_guy2 wrote on 11/04/17 at 18:28:46:



Look in tech.
It's been done.

More clearance?
Eau de Savage asked:
"For example using the 0.08—0.13 specs how bad would it be if the valves were at .2? .3?"

The analogy I used when teaching mechanics, was to think of the rocker to valve like hammer to steel. If you take a hammer, hold it very close to a piece of steel, and move the hammer, the steel moves with little trauma to the surface. If you move the hammer a distance away form the steel, and move with the same force and speed, you are more likely to deform the surface of the steel.
Valve clearances are determined to allow for almost no clearance when the valve (which is exposed to combustion heat at the large, heat absorbing end) expands/elongates.
Short answer, loose valves soon become very loose valves.

At Honda school we were taught to use two feeler gauges, or one long one folded over, on bikes with a forked rocker arm. This cancels out false readings caused by the rocker arm rocking sideways on the shaft.

Speaking of Honda school, I remember one of the guys saying that the way he adjusted valves on a twin cam 450 Honda (a bit of a PITA), was to get the bike running, loosen the clearance til the bike rattled, then tighten til the bike was quiet. Can't remember what the teacher threw at him, but it got his attention  

Yup , Just do it right

I think he might have read a old BSA manual like the one I have.
It says the valve adjustment should be "Lil to Nil" ,   I still used a feeler gauge !

Technical term , no. I have several very old manuals and they are fun to read because there is nothing technical about the old bikes. Put it together,if it starts ride it , if not try again !

LiL to NiL is a British term "little to none"  

If our bikes had a single valve per cylinder you could get pretty close doing it the way you describe. However on the savage we have two valves, therefore one valve could be .050" the other .004" and it would feel just the same as if both were .004".

I think, as someone mentioned, it would be more accurate using two feeler gauges since the rocker shaft must have some clearance and therefore some variation is probable from side to side.