I think you should take your lawn mower to another mechanic with a good reputation. He should be able to diagnose and fix the problem and save you from replacing more parts.

Well you have a sort of strange engine. It does not appear on my IPL CD but have run across it before and finally managed to get close to it on the B&S site but not the type numbers you have but not important.

I would carefully inspect the rocker arm, push rods and the stud and threads in the head for damage. IF all appears well, I would reinstall the stud torquing to 85 INCH Lbs. using some thread lock which is relatively expensive but not nearly as expensive as taking to a repair shop. Also check that the valve guide has not worked up. Should not be more than 1/8" above the head casting.

B&S went thru some "Identity crises" around this period. The 33 engine appears to be a "stretched" version of the 31 series engines which had a letter in the model number. The 31C--- has considerable differences from a 311--- for instance.

I MAY have torque settings for that and I do have detailed instructions for valve adjustment for the 31 which I would use for the 33. IF you would like them, contact me at address below, put in proper format and remind me. Note that I am experiencing computer trouble at present so don't think I am ignoring you.

Walt Conner
wconner5 at frontier dot com

I had a bent intake push rod so I replaced both intake and exhuast rods but now am having trouble adjusting the valves. I have set them to .010 because that is what I was told by a old timer but just cranks and back fires. Getting good spark and good fuel if I choke it when cranking it will kick back or back fire from to much fuel. model 331877 type 0805

.004 is best for both valves. Check that the rocker studs are secure in the head and not loose. Also look closely at each of the valve guides inside the spring. They should protrude similarly from the top of the head. If not, you have a loose valve guide. I bring this up as that can bend the push rods.

hdh3,

I have detailed instructions on adjusting your valves IF you would like them. Address below, put in proper format and remind me, model number of engine. The instructions include a compression release test along with other helpful hints.

I have the utmost respect for tomplum but do not agree that it is best to set both valves at .004".

My regular computer is off line for a couple more days, so if I don't respond promptly, it is because this back up computer has a problem.

Walt Conner
wconner5 at frontier dot com

The Briggs Check Chart states that Intake and Exhaust valves in that model range have both valves adjusted @ .004"-.006". The chart, however does NOT specifically list the 331877 model. Isn't it better to have the exhaust valve adjusted with a little larger clearance than the intake valve on these engines?

I know this is a bit old, but this MIGHT help with ID.
The 331877 uses the same crankshaft (but not piston or counter weight) as a 31C series.
From that, I'd call it a "bored" 31 series vs "stretched".

Same cam, tappets & push rods, but not head.

I thought maybe hd responded. He's probably never to be heard from again. Yes, the 28's, 31's, 33's intake spec can actually be .003" which is desirable in the long run. The singles also for some reason have ex spec slightly greater than the twins. .005 by the chart is as tight as the engineer's like. If I remember right, repair manuals tell you to make the setting in the middle of the spec, maybe not all. BTW I believe the 33's head is the same actually as a 31 -when you get a new kit, it has both gaskets, which could be interchanged inna pinch anyways. Thanks for the kind words Walt.Check's in the mail... ;)