Here's Walt's instructions that I used in Aug '07.
Valve adjustment for 28 and 31 Series B&S OHV engines
The best thing to do is buy an Overhaul Manuel for this series of engine,
about $15.
Remove the valve cover. Remove the spark plug and turn the engine to TDC
(Top Dead Center). Now some people will say that there are 2 TDCs on 4
stroke engines. While the piston does come to top twice per combustion
cycle, the TDC referred to in all 4 stroke overhaul manuals, whether auto or
lawnmower, is when piston is at the top after compression stroke. Turn the
engine in the normal direction of rotation, watch the rocker arm action to
determine when the Intake Valve has just closed, use a screw driver in spark
plug hole to feel when piston is coming up and then at top. (A better idea
is a long pencil with eraser, put the eraser end in spark plug hole) Per B&S
instructions, continue turning engine until the piston has receded ¼" down
past TDC. Put a mark on screw driver (or pencil) ¼" above highest point
reached to tell when piston has receded ¼". You will need a torques head
screw driver bit for the locking screw on tappets.
The proper setting is Intake Valve - .003 - .005", Exhaust Valve - .005 -
.007". Use a flat feeler gauge between the Rocker Arm face and the Valve
Stem. These settings are critical as the Intake setting controls the operation of the Compression Release. I usually have to make 2 - 3 attempts before I am satisfied with the setting. When you think you have the proper clearance, take a hold of the Rocker Arm and move it by hand, side to side, etc, as much as you can and recheck the clearance
setting. The nut must be held while Locking Screw is torqued to 60 inch
lbs. I recheck the clearance setting again here.
I recommend removing and reversing the Intake Valve Push Rod when adjusting
the valves. If you remove the Aluminum Intake Valve Push Rod, you will see a
worn area down a little ways from the Rocker Arm end. This is from riding on
a fiber support rub block and the aluminum push rod will eventually bend or
break. Both ends are the same and reversing will prolong the life of the
push rod.
Note: IF you remove the push rod or any other rocker arm components, there
is a cap that sits on top of each valve stem, take care that you do not
dislodge and lose the cap. It is between this cap and the rocker arm that
you actually take your clearance reading but you will not notice there is a
cap normally. (Apparently, from the Overhaul Manual, ALL engines do not have
this cap)
Replace valve cover with new gasket, torque valve cover to 60 inch lbs.,
replace spark plug.
Now I have received much flack on this site for emphasizing the accuracy of
valve setting on B&S OHV engines with some saying to leave extra clearance
"just to be sure". B&S gives a range for a reason. As I said before, the
proper operation of the compression release is dependent on the proper
setting of the Intake valve clearance. The starter of a B&S OHV engine will
not turn the engine over unless the compression release is operating.
(Unless the engine is worn out, head gasket leaking, spark plug out or some
other malfunction) I have seen many people start out by buying a new
battery, then a new starter or starter solenoid, possibly new cables or
switch when all they needed to do was adjust the valves.
As I said in the beginning, the best thing to do is buy an Overhaul Manuel
for this series of engine, if you plan to have it for any period of time,
then you will be able to see for yourself what the proper thing is to do.
Walt Conner
Torque Head Bolts
Since I do not have a way to send you a picture, I will describe the
sequence. With the cylinder head in a position where there are two holes on
your left and an open, blank, space on your right in the vertical surfaces
(you might want to make a sketch of this) - I will give the sequence going
in a clockwise direction. The open blank space I refer to is in the pushrod
gallery area.
No 1 is in the center of the side closest to you.
No. 1, 3, 6, 8, 5, 2, 4, 7.
Torque to 220 inch lbs. Tighten first round to 75 inch lbs next step to 150
inch lbs next to 200 inch lbs, then final step to 220 inch lbs. and recheck.
Tighten all bolts in sequence to whatever figure you are using.
