‘Just Parts Engines’

By Staff
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The 4-1/2 HP Jacobson restored as a 4 HP Bull's Eye (left) and the 3-1/2 HP Jacobson.
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Even if it started life as a 4-1/2 HP Jacobson, the Bull's Eye is an excellent restoration and a great-looking engine.
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The 3-1/2 HP Jacobson in its finished glory. It's almost impossible to tell that many of its parts were fabricated out of steel.
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This shot shows the outer plate in place over the bushings on the head studs and the igniter port.
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Parts built for the 3-1/2 HP Jacobson included the head, crank guard, muffler, igniter, igniter trip arm and inlet manifold.
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The fabricated cylinder head, nearly finished.

One day a few years back I was invited to look at a couple of
engines a fellow collector kept behind his shop. It seems we
collectors always need one more, so I was pleased to go along for a

There in the high grass were the picked-over remains of two
Jacobson-built engines. One was a 4-1/2 HP engine base with a
cylinder, hopper, flywheels and crankshaft, and the other was a
3-1/2 HP base with crankshaft and flywheels assembled. They were
both missing most of their small parts, not to mention major items
like heads, pistons, rods and crank guards – and the crankshaft
bearing cap was missing from the 4-1/2 HP. ‘They were just
parts engines when I got them,’ he said. Both engine bases had
a curious chunk broken out of them, and everything was suffering
from exposure to the elements. I was, of course, interested, and he
said he’d let me know if he was going to sell them. One month
later they were mine.

Now What?

I wasn’t sure what I would do with them, but I knew at the
very least the flywheels from the 3-1/2 HP could be used on my
grandfather’s Bull’s Eye, which has incorrect flywheels he
put on years ago. And I figured the other wasted relic could be
sold to a fellow I met on the Internet who could use the base and
hopper of the 4-1/2 HP to repair his Bull’s Eye, the victim of
a tornado. Now, understand that I do like the Jacobson-built
engines, and resurrecting the 4-1/2 HP engine did cross my mind.
But I knew that to bring either one of these back to life would
require a truckload of bits and pieces.

I offered the 4-1/2 HP parts to my long-distance friend, but he
couldn’t decide how much to offer for them. After hanging up
the phone with him, I began to wonder if I should keep it for
myself. Resurrecting it would take time, money, lots of
perseverance, a little help from some friends (I have no machine
tools) and it would take ingenuity to make the missing parts, which
I knew would be difficult to find.

I called a collector I know in Pennsylvania, whom I knew had
some Jacobson parts to sell. ‘Yes, I’ve got a head and a
piston – maybe a sideshaft support and governor parts,’ he
said. I picked them up the next Saturday. I didn’t inquire
about parts for the 3-1/2 HP (one challenge at a time, you know),
but he said he had a hopper and a rusty cylinder for a 3-1/2 HP
lying off in a corner. I didn’t pursue any of this, because 1
knew I had my hands full with the 4-1/2 HP project. Indeed, I did
have a lot of work to do!

Starting In

Disassembly of the few parts I had for the 4-1/2 HP revealed the
engine had been run with both flywheels loose. The machine shop
said they could take a skin cut out of the flywheel bores and build
up the crank with spray metal to get a fit. I told them not to
hurry, as there were other problems to overcome. Most curious to me
was the missing crankshaft bearing cap, the sheared cap studs, and
the 1-by 2-inch, three-cornered chunk broken out of the crankshaft
bearing saddle. I fabricated another cap, and I figured if I poured
my own crank bearings I wouldn’t need any machine work on the
cap. Drilling out the broken studs and brazing a piece of steel
into the bearing saddle got the base plate into useable

The piston had a broken skirt, and it had been welded and turned
round in a lathe – it was undersized by about 0.030-inch. The 4-1/2
HP cylinder needed to be sleeved anyhow, so the machine shop could
simply fit the cylinder sleeve to the piston. I fixed up the
sideshaft supports, repaired a broken sideshaft gear, bought some
nice reproduced flyballs and a governor spider, and brazed cracks
in the water hopper. I had to scratch-build the intake valve
chamber, inlet manifold, rocker arm and crankguard.

After about five months of spare time invested in the project, I
started to see some light at the end of the proverbial tunnel. The
machine shop cleaned up the flywheels, but they hadn’t done
anything with the crank yet. I still didn’t have a connecting
rod, and I was dreading the idea of trying to fabricate one 16-1/2
inches long. While I was waiting on the crank to be repaired, I
started thinking about the 3-1/2 HP engine and what I would need to
resurrect it, too. I knew I’d need the cylinder I’d passed
on earlier, as well as all the parts I had made for the 4-1/2 HP.
Sounds crazy, huh? I didn’t have everything in order on the
current project and I knew I still had a lot of work ahead of me,
but I had developed a sense of confidence and I was sure I could
finish whatever I started.

The fabricated cylinder head starts to come together with the
combustion chamber mounted to the base plate. The bushings on the
head studs space the outer plate.

I called back about the cylinder and found out he also had a
piston. The piston had a connecting rod with it, and I’d have
to take it all. Well, I could do that.

The piston was correct for the 4-3/4-inch bore, but it had come
from an older, headless Jacobson engine and the piston skirt and
rod were both too long. The wrist pin location was good, however,
which meant I could cut off the skirt and it would work. I measured
the rod length and – 16-1/2 inches! Here I was getting parts to
build one engine, and almost by accident I found something I needed
for the other.

I temporarily bolted my new-found and very rusty cylinder on the
base of the 3-1/2 HP engine. Like a kid with a new toy I sat and
admired it, trying to visualize what it would look like when it all
came together. Rolling the flywheels over, I noticed how large the
crank seemed to be, as though it didn’t have enough room in the
crankcase area to pull the big end of the rod around. It
didn’t, and this explained the chunk broken out of the

The early Jacobson-built 3 HP and 4 HP engines and the later
Titusville-built 5 HP engines all used crankshafts of the same
dimensions – except for the length of the throw. The 3 HP engine
had a 6-inch stroke, and the 4 HP and small 5 HP engines had a
7-inch stroke. It is possible to mount the 26-inch 4 HP flywheels
on a 3 HP engine if it has the upright governor. But it is not
possible to use the larger crank in the smaller engine (at least as
far as I could determine). For reasons unknown this 3 HP engine
base and flywheel combo had an incorrect 4 HP crankshaft, something
I hadn’t noticed. Bummer. I had just bought a cylinder, a
hopper and a piston for this engine, and realized I didn’t have
a crankshaft for it, after all. Oh well, at least I got that rod I
needed for the 4-1/2 HP engine.

Making it Work

Over the next several days I ruminated on how I could use this
crankshaft in my 4 HP engine with the flywheels that I’d had
bored oversize. Except for a very pitted crankpin surface the crank
appeared good. I figured if a guy was desperate, he might try to
wrap a shim around the crankshaft with a hose clamp to hold it in
place, make a puller and, with the split-hub flywheels, carefully
pull the flywheels on without wrinkling or tearing the shim. I
actually didn’t think it would work, but it did – and quite
well, it seems.

So, I got the flywheels on the crankshaft, but what about that
rusty crankpin? It was too late to get any machine work done on it
– after all that monkey business, I wasn’t about to take it
apart. Taking great care to maintain the radius at the corner and
measuring often, I cleaned the crankpin with some good file work. I
know this is not the ‘right way’ to do these things, but
sometimes this slow-motion old iron will accept some compromising
and be quite happy.

I made an igniter, a fuel tank and a crank guard, and eventually
got her running quite nicely. I ran it several days during the next
few months, and just before I thought it was ready to be
disassembled and sandblasted, 1 noticed a crack in two spokes on
the governor side flywheel. Not a pleasant surprise. Although I had
looked over these wheels carefully before I started the project, I
either missed seeing the cracks or perhaps they developed after
assembly. At any rate, I knew 1 would need to replace the flywheel
before running the engine away from home.

1 thought about having a flywheel cast, but decided that might
be a little rough on the family budget. I figured there was little
or no chance of finding something used, but I got up my nerve and
called around anyway. I almost dropped the phone when one person I
called said, ‘Yes, I’ve got two, but they’re on a
crankshaft and I don’t want to break it up. You’ll have to
take it all.’ I didn’t need an extra crankshaft and
flywheel, but as you may already know, we collectors better take
what we can get and not worry about a few extra parts scattered

Inspecting my latest acquisition and seeing how good the
crankshaft looked, I decided to clean it up and possibly use it
with the two new flywheels as a unit in place of the less than
perfect arrangement I had created. Oh wait, another surprise. Those
two 4-1/2 HP flywheels were actually hung on a 3-1/2 HP crankshaft!
What luck! (They say even a blind hog can find an acorn once in a
while.) That crank and sideshaft gear could be used to rebuild the
3 HP engine. Once again, while getting something for one engine I
unknowingly got something for the other.

Within a couple of months I had painted the 4 HP engine red, had
it striped, fabricated wagon parts and bought a reproduction tag –
it was looking better than new.

Final Push

By virtue of the odd nature in which this had all fallen into
place, I now had all but two of the critical parts needed to begin
resurrection of the 3-1/2 HP engine. I advertised for a cylinder
head and began to search for a 13-1/2-inch connecting rod. I
eventually found a connecting rod (although it had no cap), but I
never got any calls or even a lead to a head.

‘I’ll have to try to make a head,’ I told my
neighbor, who had helped me make some of my parts on his lathe. I
asked him to make six bushings to fit over the head studs and a
valve seat that I could weld into a 2-inch section of square tubing
that I planned to use for the combustion chamber.

I started on the inside and worked out. I decided a 5/8-inch
plate against the cylinder and a 1/2-inch plate on the outer end
would work to sandwich the pre-finished combustion chamber. The
real challenge was preparing and assembling the pieces so all of
the joints could be welded. It’s home-style engineering, and of
course it’s not ‘correct,’ but it works for me.

I created several other parts, some out of necessity, and some
just because I wanted to. You can buy the governor sleeve, spider,
crank guard, muffler, igniter, igniter trip arm and inlet manifold
as reproductions. I bought a reproduction mixer, a timer and a cap
for the inlet valve chamber, along with a nice cast iron water
drain valve.

I realize fabricating imitation parts from steel is not as good
as using castings made from a pattern, and I would only recommend
doing what I did to desperate and crazy people, like myself. Making
parts this way is tedious and dirty work, but I could not have
brought these two discarded relics back to life without making what
I could not buy. Remember, ‘they were just parts engines when I
got them.’

Contact engine enthusiast Art Lora at: 12895 Duck Creek
Road, Salem, OH 44460, or e-mail: sparky19@raex.com

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