Homemade 7 HP Economy

By Staff
article image

1222 Deep Creek Road Manhattan, Kansas 66502

A little story about a repowered B John Deere-I had an old 7 HP
Economy which was in bad shape. The cylinder was rusted and pitted
very badly, no mag of any kind other than it was all there. I
cleaned it all up, put some rings in it, and installed a Wico trip
mag. I made the trip assembly plate to go where the ignitor
originally was. I had to make a gas tank as the old one was rusted
away. Anyway, I got it running and it ran okay, some blow-by, but
not that bad.

I had been thinking about putting this engine in an old farm
tractor, for some time. I decided to use a John Deere B, as I could
belt to the flywheel and have the clutch, belt pulley, and
transmission work like it always did.

I got a 1941 John Deere B and started to work. I removed the
head and block assembly, fan drive, radiator, governor and mag
housing. Removed pistons and rod. I plugged oil holes in rod
journals as I needed to keep the oil pump to feed main bearings,
cam and oil pump drive. (Didn’t need cam but it drives the oil
pump). Made a plate to cover the front of the crankcase. Also made
a cover over top of the cam gear and plate cover on top of the pump
drive. I installed a pressure gauge here, as it would have pressure
like always.

This was a long frame B (maybe all the later ones were?), but I
still had to lengthen the frame eight inches. I cut the bottom
angles out of the frame to set the Economy as low as I could since
the engine is very heavy. I made hangers to set the engine on, and
they are 6′ below the bottom of the tractor frame.

Now, to belt up. I didn’t want to run a twisted belt, so I
decided to change the rotation on the engine. This was easy because
the cam bob was riveted to the cam gear. Next, I removed the
rivets, turned the bob over, re-riveted it and retimed the gear. It
starts easy and runs good but it’s terribly out of balance. At
about 250 r.p.m. it bounces the tractor bad, but above or below 250
it’s not as bad. When it’s moving you don’t notice it
much. The engine was designed to run one way and when you reverse
it, the torque and thrust change. Someone told me to cut new
keyways in the crank and change the flywheels 180 degrees.
Personally, I don’t buy that, but I may be wrong. I haven’t
and probably won’t do this. Anyone who can shed some light on
this, I would like to know their view.

Now back to belt up. The flywheels are 34′ diameter, and the
tractor flywheel is 17′. This would only give me 600 on the
tractor, with the engine at 300, which is as fast as I want to run
the engine. I thought that would be too slow for parades, so I put
a 14′ V belt shiv behind the tractor flywheel and used a V
belt. It stays on the 34′ flywheel okay and pulls all the
engine can put out.

The speed is about right now, and I still have enough power to
pull up on the trailer or pull a light load. I had to come up with
wheels, since the tractor had no wheels when I got it. New tires
for the front and rear were put on it. The rears are 9.5 x 36.

As for the time spent on this project: about 6 months of my
spare time. This was winter and spring of 1990.

I have been in about six parades and several engine shows. It
draws a lot of attention and remarks.

I also have a 11/2 HP JD engine that I put
on an old garden tractor frame. My grandson drives it and it runs

Gas Engine Magazine
Gas Engine Magazine
Preserving the History of Internal Combustion Engines