Vintage Tecumseh Identification
Article by Mark Trotta
Modern Tecumseh engines are easily identified by an engine ID label, usually found under the engine cover. But if yours is 30, or 40, or 50 years old, engine ID will require a little more looking.
Pictured: 1968 Tecumseh H25
Early Tecumseh engines (up until mid-1970's) have a nameplate riveted to the square end of the block. Mid-1970's and later have ID numbers stamped into the flywheel shroud.
Engine Identification Plate
On early Tecumseh engines, there is a metal identification plate on the blower housing held on by two rivet-screws.
If the engine ID plate is still there, it'll tell you all you need to know about the motor. The first line on the tag, the word "MODEL" appears.
In this example, the "H" denotes horizontal-shaft engine.
Engine Model Codes
- H = Horizontal Shaft
- HS = Horizontal Small Frame {engine}
- HM = Horizontal Medium Frame {engine}
- HHM = Horizontal Heavy Duty {cast iron} Medium Frame {engine}
- HH = Horizontal Heavy Duty {cast iron}
- V = Vertical Shaft
- LAV = Lightweight Aluminum Vertical {engine}
- VM = Vertical Medium Frame {engine}
- TVM = Tecumseh Vertical {medium frame}
- VH = Vertical Heavy Duty {cast iron}
- TVS = Tecumseh Vertical Shaft
- TNT = Toro N' Tecumseh
- ECV = Exclusive Craftsman Vertical
- OVM = Overhead Valve vertical Medium Frame {engine}
- ECH = Exclusive Craftsman Horizontal
The numbers after the letter indicate horsepower. For example, an H25 was 2-1/2 horsepower, an H30 was 3 horsepower, etc. Following that is a group of numbers that tells you the sub-model within the H25 family.
Manufacture Date
The second line on the identification tag starts with "SERIAL" followed by four numbers. These tell you the date of manufacture.
The first digit will be the last digit of the year. For example, "8" could mean either 1968 or 1978, but since the H25 was not made after 1974, that identifies this engine as a 1968 production.
The next three numbers are the calendar day of the year. Since 1968 is not a leap year, 275 is October 2nd. That means this H25 Tecumseh engine was produced on October 2nd, 1968.
The last set of digits on the ID tag is the engine's unique serial number.
Missing ID Tag
You may have an early Tecumseh engine whose ID tag is missing or unreadable. To help determine what year and model engine it is, you may need to remove the cylinder head and measure the cylinder bore and stroke. But there are a few ways you can estimate what year the motor is.
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Starter Housing
Early Tecumseh engines have "teardrop" shaped starter housings, which are metal and attach to the blower housing with four rivets.
Tecumseh engine with teardrop starter housing.
Later engines had "stylized" starter housings with thin slots arranged in a circle.
Tecumseh engine with stylized starter housing.
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Metal vs Plastic Gas Tank
There are several visual cues to "ballpark" the year of an old Tecumseh small engine. Up until the mid seventies, gas tanks were metal. After that, gas tanks were plastic.
The plastic gas tank on this purple Tecumseh motor tells us it's a late 1970's or newer.
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Exhaust
Several styles of exhaust were seen on Tecumseh small engines.
The odd-shaped muffler on this motor helped identify it as a 1981 H35 model.
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Points vs Electronic Ignition
Another way to determine the approximate year of a Tecumseh motor is by the ignition system. A capacitor discharge ignition was first offered in 1968 on their cast-iron engine models. Around 1976, electronic ignition became standard equipment on vertical-shaft engines (such as lawn mowers, etc).
Read: Tecumseh Points Ignition Repair
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Best Spark Plug for Tecumseh Flatheads
Very early flatheads were fitted with a Champion J8 spark plug, which is now obsolete and expensive when found. The modern replacement is Champion J8C, which looks slightly different, but works the same and takes the same 13/16" wrench size. It is sold as stock # 841.
Somewhere in the 1970's, Tecumseh replaced the J8 spark plug with Champion RJ17LM.
Today, the most common spark plug found in old Tecumseh flatheads is the Champion RJ19LM, which is one step hotter than the RJ17LM.
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Tecumseh Side Popper
The "side popper" nickname was given to Tecumseh engines that had side exhaust instead of rear exhaust. These were seen during the 1970's on gas-powered lawn equipment, as well as several brands of mini-bikes.
Tecumseh side-popper engines don't perform any better than conventional motors. But, because many were fitted to 1970's minibikes, they are very desirable to small engine collectors.
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Decal Style
Sometimes you can tell the approximate age of an old engine by the decal type. Tecumseh affixed several styles of logos to the engine's blower housing. But very often, due to the passing of time, the decals are often missing or no longer visible.
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Engine Colors
Most old Tecumseh engines were originally painted either red, white, or black.
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Related Articles:
Vintage Tecumseh Engine Build
Tecumseh Crank and Connecting Rod Inspection
Integral Valve Seat Repair
Tecumseh Points Ignition Repair
