Vintage Briggs And Stratton Identification

Article by Mark Trotta

Every time I visited my friend's workshop, I noticed the old Briggs flathead he had propped up on a shelf. I wondered how old it was, and if he would ever part with it.

After I had dismounted some worn tires off a set of old truck wheels for him, he said, "How can I repay you?"

"How about selling me that old Briggs motor over there?"

"Oh, you can have that."

So, I became the proud owner of a non-running, older-than-me, vintage Briggs & Stratton flathead. With the exception of the missing gas tank and air cleaner, the engine is complete and original. I'm hoping that the missing parts can be easily located, but first, I had to find out what year and model the motor was.

Identifying Vintage Briggs & Stratton Engines

On vintage B&S motors, an ID plate was mounted to the blower housing next to the intake port. Later Briggs engines had ID numbers stamped into the blower housing, on the carb side near the top outside edge.

The ID tag is the easiest way to identify a vintage Briggs engine.

Missing Identification Tag

When you encounter an old engine with no ID tag or numbers on the housing, there are other ways to determine what year and model it is.

With a magnet, check if the block is aluminum or iron, and count the number of cylinder head bolts.

Typically, aluminum Briggs engines have ID numbers stamped into the blower housing.

How Can I Tell It's The Original Blower Housing?

A blower housing, along with it's with decals and ID, can easily be swapped from one engine to another, so it's not a completely accurate way to determine which engine you have.

If you're not certain it's the original cover, you won't really know what you have until you measure the engine bore and stroke. Opening up the motor helps solve other mysteries, too, like if an overhaul or modifications have been done.

To be certain what you have, remove the blower housing and cylinder head. When dealing with an unknown vintage small engine, measuring the bore and stroke is the best way to tell what engine you have.

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Identifying Cast-Iron Briggs Engines

Identifying Aluminum Block Briggs Motors

This old Briggs motor is cast-iron and has 6 head bolts, so it's either a model N, 5, 6, or 8. To help narrow that down, I measured the cylinder bore and stroke. The piston bore was 2-1/4 (2.25) inches and the stroke length was 2 inches.

Briggs & Stratton With 2" Bore

What The Numbers And Letters Mean

Briggs & Stratton With 2-1/4" Bore

After measuring a 2-1/4" bore with a 2" stroke and having a 6-bolt head, this engine is either a Briggs model 8 or model 9. The horizontal-split cast iron block and aluminum base helped me determine that this engine was a new style 8 series.

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Briggs 5S vs 6S

Briggs 5S (five-S) and 6S (six-S) engines are fairly common. The main difference between the two is the length of the piston stroke (1.50" vs 2.00"). These engines were found primarily on lawn and garden equipment, but also on vintage scooters and minibikes. A 6B-S looks identical to a 6S, but it has a cast aluminum block instead of cast iron.

Read: Briggs & Stratton 5S Engine

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Briggs & Stratton 60000 Series

In 1957, the 5-series engines were discontinued, and the 6-series were replaced with the "60000" series, which had a different bore and different stroke.

Briggs & Stratton 80000 Series

Most vintage Briggs motors built before 1965 will have a date code stamped on the flywheel and/or magneto plate. The last two digits of the year are shown in one casting, followed by a letter representing the month. The months are coded in letters; for example, A = January, B = February, etc.

Briggs & Stratton With 2-1/2" And Larger Bores

Briggs & Stratton PB Series

Briggs & Stratton 90000 Series

Briggs & Stratton 100000 Series

Briggs & Stratton 100700 Series

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Briggs W Series Engines

Primarily designed to power washing machines, the WM motor was produced from 1936 to 1941. The visual identifier is the spark plug; it mounts horizontally into the cylinder head. Other versions of this motor were the WMI and WMG.

An improved version of the WM, the WMB and WI engines, were produced from 1938-1957. These motors have the spark plug mounted vertically in the cylinder head.

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Round vs Flat Air Cleaner

Another age identifier is the engine air filter. Early Briggs engines had a round oil-bath filter secured by a wing nut on top of the carburetor. The bottom of the canister gets filled with oil.

Round air filters were phased out in the mid 1960s, and replaced by the flat, kidney-shaped gas tank shown here.

Champion J8 Substitute

Briggs & Stratton fitted a Champion J8 spark plug to many of their old engines. These are now obsolete and expensive when you find them.

The modern replacement for the J8 is Champion J8C, which looks slightly different, but works the same and takes the same 13/16" wrench size.

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Briggs Stratton Logo

Throughout it's history, Briggs & Stratton had a variety of logos with different shapes and colors. Very early engines had a brass ID tag on the blower housing.

The first gold logo was used from 1948 to 1963. Appearing on the original gold decal is the name "Briggs & Stratton" with "Milwaukee, Wis., U.S.A." below it. The middle of the decal has the words "4 CYCLE" on the top mast and the words "GASOLINE ENGINE" with "MADE IN U.S.A." on the bottom mast.

A second gold logo was seen from 1963 through 1976.

Although similar to the early logo, the wording was arranged differently. The name BRIGGS & STRATTON was written in a new logo type, and engine horsepower rating was included above the gold logo. The city of location was in the middle as before, but the patent numbers were eliminated.

Some Briggs engines produced in the seventies were factory fitted with the earlier logo, so there are exceptions to the early/late logos.

Mid 70's and Up

The red, white and black Briggs & Stratton logo began in 1976 and is in use to the present day. The logo hasn't changed much since, although the wording on the top and bottom sections of the mast were removed in 1985.

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Although it's been 25+ years since production ended, these "L-Head" motors are still very popular.

Briggs 3.5 HP Flathead Engine

Briggs 5HP Flathead Engine

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Briggs & Stratton 5S Engine

How To Restore Engine Tin

Best Fuel For Small Engines

Read: Briggs Tank-Mounted Carb Repair