Valve adjustment. Just like the dozens of other posts about hard starting Briggs OHV engines.

How often do you have to adjust the valves and what is involved in doing so. Thanks

I think B&S suggest the valve setting be checked once a year. Some go 6 - 7 years, some need it in a couple.

I have detailed instructions for adjusting valve on 28 and 31 series engines. IF you would like them, put address in proper format.

Walt Conner
wconner5 at verizon dot net

I checked the valves last night. Within specs but then I started thinking. If they were way loose that would not matter on the compression stroke (both valves would be closed)and thats where the problem is. Must be the starter.

"I checked the valves last night. Within specs but then I started thinking. If they were way loose that would not matter on the compression stroke (both valves would be closed)and thats where the problem is. Must be the starter."

Well that is where you are mistaken. The Compression Release holds the INTAKE Valve open just a hair well into the Compression Stroke to relieve compression. The Intake Valve adjustment is what is critical. .003" - .005" at 1/4" down past TDC. and is the most common cause of the symptoms you mention though other things can cause it. Usually people start out buying a new battry, then a new starter, starter solenoid, on and on when all they needed to do was adjust the valves.

Walt Conner

Davefin: Please listen to what Walt is telling you. He also sent me the instructions on valve adjusting, and it made a huge difference in my B&S 18 hp Vanguard engine. He knows his stuff.

My B&S OHV book says to set the clearance at .003-.005 TDC. Are you saying just a tad past tdc adjust the valves? What is the compression release feature you are refering too. I dont see this mechanism on my engine. I have a 31p777 Thanks

Well model numbers matter. You never have posted the model numbers of the engine but all the 18 hp single cylinder OHV B&S engines I have seen are Inteks which set at 1/4" down past TDC. Now Intek OHV TWINS in the early instructions said at TDC, later as I understand it, they also said 1/4" down after TDC which is standard for most B&S engines.

IF you have a Repair Manual for B&S single cylinder OHV engines, might want to recheck it.

Walt Conner

As Walt said-
"The Compression Release holds the INTAKE Valve open just a hair well into the Compression Stroke to relieve compression."

At TDC, the Intake valve is actually opened SLIGHTLY.
IF you have clearance at TDC, the compression release CANNOT function.

Walt has excellent instructions, which also includes some caveats about what NOT to do.

You came here asking for advice. Have you received any that told you NOT to adjust the valves?

Walt, please send me a copy of your OHV valve adjustment procedures. That HAS to be wrong with mine.

jbo_c@yahoo.com

Thanks.

Hi Walt, could you please send me a copy of the valve adjustment procedure. Thank you for your time.

Joe

jmdfxdt@yahoo.com

Hello Walt, first I want to thank you for the time you and others put into this forum, I read it regularly but almost never post since the only garden tractor I use is an old Dynamark I use about 6 hrs/year for spraying Round-Up . Having said that, I'm gonna jump on the bandwagon and ask you if you'll send me the instructions for setting the valves on a BS. I've got a 60" pull-behind Swisher finishing mower (w/13.5 hp BS) that I use off-set behind my 154 Cub Loboy and have been adjusting the valves basically by trial and error. My email is DixiWillie@aol.com
TIA, Stan Wilhite in N AL.

if the intake valve is open a hair then yo have either a worn camshaft or a broken cam spring. Briggs engines are known for this thats why we tell our customers to stay away from all briggs engines they are JUNK.

I have a 20 HP Single Briggs & Stratton Intek engine. The mower probably has maybe 6 hrs. on it. Last night when I shut off the motor it back fired......is that normal? I'm also wondering the proper way to shut off my engine.......should I throttle all the way down before turning the key in the off position? Any info will be greatly appreciated.

"Briggs engines are known for this thats why we tell our customers to stay away from all briggs engines they are JUNK."

Well that is a bunch of baloney.

Walt Conner

I feel kind of stoopid suddenly. Someone please explain how a "worn camshaft" will cause either of the valves to remain OPEN.

ab26, if your engine has a "fuel solenoid" in the carb bowl, you should shut your engine off at high RPM by turning off the IGNITION SWITCH. The solenoid has a plunger valve that shuts off the flow of gasoline to the MAIN JET. The solenoid is used to prevent the phenomenon known as "afterfire" (which is what you heard). It works like this: If you shut off you engine by moving the throttle to the idle/off position, you kill the spark ignition but gasoline continues to be fed to the intake of the engine (because the solenoid is still energized). This fuel air mix is now just passing through the cylinder and out the exhaust valve without ever combusting in the cylinder. The exhaust pipe and muffler are saturated with extreme heat from use. So long as the fuel/air mix is passing through the exhaust system at a pretty high velocity....no "afterfire, or ignition" can occur because the mix is whisked through without being able to heat to the point of spontaneous ignition. BUT, as soon as the crankshaft and pistons stop moving......so does the fuel air mix and at that point the blazing hot surfaces in the exhaust system instantly raise the temperature of the mix to the point of spontaneous combustion and BANG is the result. Now, when you shut down your solenoid equipped engine at high RPM by turning off the IGNITION SWITCH, this is what happens: Turn key off, fuel solenoid closes depriving the engine of its main jet fuel. Engine immediately burns the last puff of fuel mix in the normal fashion (because the spark ignition is still firing the plugs). As the last of the gas is burned, the engine RPM sudenly dives toward zero, all the while the engine is being purged and ventilated by the air that continues to flow (minus fuel of course) through the engine and out the exhaust. Because fuel is absent, when the engine finally stops at zero RPM under these conditions, there can be no "afterfire" bang.

"if the intake valve is open a hair then yo have either a worn camshaft"

"Someone please explain how a "worn camshaft" will cause either of the valves to remain OPEN."

Good point, sort of goes along with his other statement.

Walt Conner

If it's only a worn camshaft, the lobe tops would be rounded off and there would be less lift to the valves, so, if anything, they'd open less and if readjusted to open the correct amount with worn lobes, the duration would be changed.

I'd also think that in an engine that was worn-out or neglected to the point the cam was worn, one might also find bad valve seals and seats that would lead to leaky valves at any clearance setting and make finding the "correct" setting almost impossible.

-Ed