OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines 2.5hp Briggs

Hi all. I'm not sure if I have seen this type of carby standard on a 2.5hp Briggs or am I thinking of the 2hp version. Can someone please put me straight?
Model 80102
Type 0233-01
Code 75081503

Your engine was made on 15 August 1975. Here is the Illustrated Parts List:
http://bsintek.basco.com/BriggsDocumentDisplay/Z6jmvGVJ1DajI.pdf

Here is the Operator's Manual:
http://bsintek.basco.com/BriggsDocumentDisplay/lrvvA-wU7eL7hAxB91ObQ.pdf

Your engine's model number, 80102, tells you quite a bit about it. The first digit tells you it has a displacement of 8 cubic inches (130 cc). The second digit says it is of the very first design generation after Briggs adopted its standard model numbering system. The third digit means it has a horizontal crankshaft and a Vacu-Jet carburetor. The fourth digit signifies that it has plain main bearings, not ballraces, and it does not have a flange mount, or gear reduction, or any form of auxiliary drive. The fifth digit says it has a rewind starter.

For your immediate purposes the key point is that it had when it was new, a Vacu-Jet carburetor, not the more elaborate Pulsa-Jet. However your picture shows that it now has a Pulsa-Jet. (Note that it still has the Choke-A-Matic coupled choke, which was available with both carburetors). That means somewhere along the line, someone has converted your 80102 into an 80202, as far as carburetor and fuel tank are concerned. In case you care, the simple way to distinguish between Vacu-Jet and Pulsa-Jet on that generation of carburetors, is that the pull-knob on the choke is horizontal on the Vacu-Jet and vertical on the Pulsa-Jet.

The Pulsa-Jet has a built-in fuel pump, while the Vacu-Jet relies purely on venturi vacuum to draw fuel up from the fuel tank. The Vacu-Jet was not really satisfactory with the deep fuel tank which your engine has - the Pulsa-Jet does not let the mixture lean out when the fuel level in the tank is low. Presumably someone switched the tank and carburetor as an assembly, so as to make a shallow-tank engine into a deep-tank engine. I believe that model mower was, over time, fitted with all combinations of carburetor and fuel tank.

Getting down to minor points, being made prior to 1982, your engine had a breaker-point ignition system when it was new. It is commonplace for people to convert those engines to electronic (Magnetron) ignition, though, if the breaker-point system gives trouble. Generally it is easier to do that than to replace the points or condenser, and it makes the system more durable. You would have to remove the cooling air cowl to find out whether it has been done to your engine.

Silly question.....to convert from points, is the only change the coil?

Hey grumpy. Seems as I thought, something wasn't quite right with this engine. Ok the carby may have been converted, or to throw a spanner in the works could it have been the cowling that's been exchanged (perhaps the starter cord broke so someone just swapped the whole cowling)therefor showing the 2.5hp decal and code numbers to suit instead of what may have been originally been a 3hp engine? The reason I'm inquiring is because I would like to refurbish the engine and have the correct decals to suit. Please correct me if I am wrong but I guess the only way to tell for sure is to take the head off and measure the stroke and bore. The engine does have breaker points which I had to clean and adjust to .020'' because it had little spark and would not start.

Hi Bergy,

It is difficult to tell what has been swapped from just the pictures. The only other distinguishing feature I can see is a paddle kill switch on top of the head. Of course, you can also see that the spark plug doesn't come with a boot.

The hacked-up cowling indicates a need to free the governor linkage to stop it from binding.
That is some obvious tampering/modification. Perhaps the problem is a different type, bent or custom/homemade linkage?

It is rare for the bore to be in good nick after so many years, unless the engine has had regular oil changes and the air filter has been cleaned/replaced often. To refurbish an engine of that vintage, sooner or later you'll want to remove the cylinder head anyway, to check the condition of the bore, piston, rings and valves. Afterwards, you'll need to decarbonise everything before reassembly.

To convert that Briggs to electronic ignition, all you need is the Magnetron unit from a later engine of the same cubic capacity. (It has to be from an engine with the same flywheel size, or it will not fit your engine.) Note that the Magnetron module looks the same as the coil you currently have, but if you look closely you'll see the switching device packed in between the coil and the magnetic yoke. There is a spade connector for a low-tension kill switch (as there is on the later breaker point coils) since only the very early design generation engines used the spark plug shorting system for a kill switch. If you continue to use the plug shorting facility, you just ignore the spade lug. The old coil unit has a wire coming out of the coil running to the breaker points. The Magnetron does not have that wire, so you just cut it in some convenient place so that the part of the old wire near the crankcase does not foul on anything.

There are three coils used on aluminum crankcase, single cylinder Briggs to convert from breaker point condenser to electronic as follows:

398593/395489/793281 are used on 2hp to 4hp engines, such as 60000, 80000, 90100, Quattro, and Classic

397358/697037/395490/395491 are used on 5hp engines such as 130000 series flat heads

398811/395492/398265 are used on 7hp to 16hp single cylinder engines, such as 170000, 190000, 280000, and 310000.

These do not work on cast iron crankcase engine as these have reverse polarity flywheel magnets.

Thanks for posting that AVB - a very useful summary which I have not seen anywhere else.

By the way, believe it or not the cast iron Briggs engines are too old to be found at all commonly even here in Australia where old mowers tend to be treasured. The reason is that the Australian government levied fearsome import duties on just about everything that didn't come from Britain until the 1980s, which meant engines were nearly always British, American models assembled in Australia, or of unique local design. I can tell you, finally getting access to ordinary side valve Briggs engines after the late 1970s was a considerable improvement in many people's lives.