For several years, I toyed with the idea of building an engine
out of an air compressor. Each time I saw an article in Gas Engine
Magazine about another homemade creation, the interest was
rekindled, only to fade each time for a lack of resources –
especially because I didn’t own an air compressor.
After I completed a Briggs & Stratton Model FH restoration
for a friend (January 2004 GEM), I set my sights on an
overhead-valve Briggs. Since retirement income precluded the
purchase of such an engine, I decided to make my own and call it a
Briggs & Stratton Model ‘KH.’
I started with the crankcase from a 3 HP horizontal-shaft Briggs
& Stratton Model 82000, but it was missing several components
including valves and a connecting rod. I appropriated these parts,
as well as the crankshaft, flywheel and ignition coil, from a 3 HP
Briggs & Stratton vertical-shaft lawn-mower engine of older
vintage.
When I told local old-iron enthusiast Don Spero what I was
planning to build, he said he had something that just might be
useful for this project. The next day, he presented me with a
sealed box. When I opened it, I found a brand new aluminum head,
complete with installed valves and attached rocker arms! A quick
check revealed the head was made for a cylinder with the same
2.375-inch bore as the block I was using to make the Model
‘KH.’
Getting to Work
One problem became immediately apparent, however. My original
plan was to use an atmospheric-intake valve and bring the
exhaust-valve pushrod up through the original valve guide. That
plan was impossible with the new head assembly since its valves are
mounted at an angle, and the rocker arms protrude beyond the side
of the head.
About this time, John Heath’s article about his Curtis Crudo
homemade engine appeared in the September 2003 GEM. Taking some
inspiration from John’s Crudo design, I decided to move the
tinning gears and camshaft outside the crankcase as he had
done.
I fabricated adapter plates to mount the head assembly,
carburetor, muffler and the U-shaped mount for the timing gears
from 3/8-inch-thick aluminum. I brazed a shaft bushing to the small
timing gear so it could be secured to the crankshaft. I made the
flywheel from a 10-pound barbell weight, which I trued on the lathe
and bolted to a lawnmower blade holder. For a gas tank, I used a
5-inch length of heavy-wall copper tubing. I made the end caps from
the bottoms of 15-ounce vegetable tin cans that I soldered in
place.
I had planned to use an old Clinton carburetor from my junk box
for this project, but it posed a special problem since someone had
turned the idle-adjust screw in so tightly it had jammed and broken
off. I drilled out the needle passage, tapping it to a 1/4-28
thread, and made up a new insert complete with an air passage,
idle-bleed jet hole and a new 8-32 thread idle mixture screw.
The cast iron flywheel and the ignition coil I salvaged from the
lawnmower engine were designed to use breaker points and a
condenser. The crankcase I used featured breakerless ignition, so
it had no provision for mounting and operating breaker points.
Initial attempts at operating a micro-switch from the exhaust-valve
camshaft produced a marginally adequate spark. Rummaging through my
junk box, however, I found an original Briggs & Stratton
conversion kit designed to replace the points and condenser on
early B&S engines. I had purchased this unit many years ago but
never used it. After installing it, the spark was extremely hot,
and ignition timing was automatically established.
The governor also caused me some head-scratching because the air
vane was located on one side of the engine, and the carburetor was
located on the opposite side. My final design uses coat-hanger wire
and two 90-degree pivot points with the final link to the throttle
shaft passing through the center of the hollow rockerarm shaft.
Finally, I added an air cleaner housing made from a tuna fish
can.
Upon completion, the engine started on the very first pull and
ran very smoothly after minor mixture adjustments. This project
gave me a lot of satisfaction because it forced me to face each
challenge and devise a solution that resulted in a nice-running
engine. It is definitely one of a kind.
Contact engine enthusiast Ken Hollenbeck at: 607 Cherrywood
Lane, Sister Bay, Wl 54234; (920) 854-2461.
