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I have a 1982 5hp B&S engine. Here's the info from the name plate.
MODEL TYPE C0DE
130202 0198 07 82042807
For several months, I've been fighting a persistent problem with this engine, which was on my late father's rototiller, and which I'm trying to restore. Although the engine starts easily and reliably and has good power, it is popping. Not big back fire pops, but smaller very frequent pops. The plug is very wet and black with what I assume is fuel. I took it to a local repairman who said it was the carb and I should junk the engine. I didn't believe this because the engine ran so well. ( I've plowed up a lot of ground with it, very successfully. ) But I really want it to run properly, so I bought another carburetor, an OEM B&S in genuine packaging. The problem stayed the same. Maybe a tiny bit better. I can also smell exhaust really bad. I've repeatedly adjusted the one screw on the carb as instructed on B&S web page. All the way in then, back it out slowly 1.5 turns. This makes no difference in the popping or the fuel on the plug. How in the world can I get this engine to stop running so rich and dumping fuel ?

Thanks,
Tom

Forget to mention- the spark plug is new.

Two things I would check is
Is the air filter clean and unrestricted?
Is the choke valve opening fully?

Something else to consider is that engine is old enough to have issues with valve sealing. Over time the valve face and seat wear and cause issues with floating valves because you loose your valve clearances.

i've also had problems with a valve seat coming loose, runs ok but does what you're describing. The seat can be put in place and staked to secure it. Maybe a 1 in 100 chance this is it - thankfully.

Points.

Replace the coil with the newer version with ignition chip inside.

Just clip the wire to the points, and pop on the new coil, and go.

Hook up the kill wire, if it has one

No need to remove the flywheel.

Thanks! I'll get a new coil with ignition chip. Umm....showing my inexperience here, but how can points/ ignition have anything to do with oil being dumped out the exhaust, onto the spark plug and all over the air cleaner? I sniffed the fouled plug and it is not fuel but oil. And there is oil on the tiler frame just below the muffler. Also, if the valves were sticking/floating, would there be a commensurate loss of compression? I ask because the engine is so incredibly easy to start that it seems to have good compression. I'll borrow a compression tested from Autozone and test it, just to be sure. I also replaced the valve cover which was leaking oil.

When did oil coming out the exhaust come into the discussion?

The oil is likely from turning the engine on it's side to work on it. It will burn off after a while.

Your running/starting problem is likely your engine's old points/condensor ignition, older folks know about things like this. Briggs switched over to the electronic ignitions @ 1983-84. The first ones came with the old coil with the update module attached. Later ones were just equipped with the newer electronic coil.


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I don't think think you have a spark issue. If the engine has a lot of hours on it it probably has worn valve guides which is just holes in the aluminum block. This is a weak point on that 5hp engine. Take the head off and check for side play in the valves. Should be very little. If guides are worn new brass guides can be installed by a shop if the have the tools. Haven't used mine in many years. Oil in the exhaust is either worn rings and cylinder or the crankcase breather is plugged. On the side of the block is a cover to access the valve springs. This is the crankcase breather. It has a disk valve in it and 2 oil drainback holes. If the valve it stuck or the holes plugged you will get oil in the cylinder. If the oil was not changed on a regular basis that aluminm bore engine will probably have a worn cylinder. It can look smooth but have low compression. Because of the easy spin bump on the intake lobe of the cam a compression tester won't tell you much. You need to do a leakdown test to determine the condition of rings and valves and that won't find bad valve guides. If you really want to save it you can get the proper ball hone and deglaze the cylinder and put in new rings and have new guides and valves installed. Will cost more than the tiller is worth probably. When you replaced the valve cover did you orient the drainback holes at the bottom? And the gasket nitches at the bottom? If not it will fill with oil and blow oil into the cyoliner

Is the oil over filled? Valve seals might need replaced. Oil rings might be bad.

slomo