1919 Fairbanks-Morse Plugoscillator Engine Restoration – Part 2 of 2

By Staff
1 / 22
Peter Rooke's 1919 Fairbanks-Morse 3 hp Type Z Plugoscillator.
2 / 22
The engine base casting, cleaned and ready for primer.
3 / 22
The underside of the base with fuel tank installed.
4 / 22
The engine block, painted and ready for assembly to begin.
5 / 22
Shaping the backside of the muffler.
6 / 22
Starting to dome the muffler. The former is to the right.
7 / 22
The dome shaped, ready for planishing and trimming to size.
8 / 22
The completed muffler with connector pipe welded in place.
9 / 22
Red paint left in rust pitting on exposed parts of crankshaft.
10 / 22
Same area after spraying with silver metallic paint and sanding.
11 / 22
Using a valve spring compressor to aid in exhaust valve removal.
12 / 22
Reforming a spring to match the diameter and shape of the original intake valve spring, which was badly rusted.
13 / 22
The throttle butterfly valve.
14 / 22
The restored governor assembly with butterfly crank arm reset.
15 / 22
Broken igniter trip finger. Compare this with the fixed trip at bottom.
16 / 22
The finger end of the trip ground to a knife edge for welding.
17 / 22
Ready to weld the finger tip repair to the trip arm.
18 / 22
The repaired and finished igniter trip arm.
19 / 22
Fitting shims to the connecting rod big end at the crankshaft.
20 / 22
The fuel tank drain tube.
21 / 22
Setting ignition timing, with tape to mark TDC and 22.5 degrees BTDC.
22 / 22
The finished engine.

This is the second part in a two-part series on Peter Rooke’s 1919 Fairbanks-Morse Plugoscillator engine restoration. Read the first part here. 

In addition to being the wrong color, the existing paint on the engine was beginning to show signs of rust spotting through. Rather than just lightly sanding the existing paint and repainting, this engine needed a complete strip down and the application of a good zinc-based primer.

The old paint was removed using a combination of disc sander, wire brush and scrapers. Once down to the bare metal the majority of any rust was sanded off, leaving only some pitting. To protect the cylinder bore during the cleaning process, both ends were plugged with clean rags.

To control and prevent further rust, the engine and its parts were given two coats of a high zinc cold galvanizing primer, which was thinned a little to give good, even coverage.

The primer paint was very soft and could be rubbed off easily, so all parts were given a quick coat of enamel paint as soon as the primer had fully dried. The first coat of enamel was left for at least a day to thoroughly dry before applying a second coat. After leaving the second coat of enamel for a few days to cure properly, the surface was given a very light sand with 280-grit wet and dry paper to remove minor blemishes.

The final coats of paint should be applied in a dry and well-ventilated environment that should be free from dust and any other contaminants. The ambient temperature should be constant, and if heating is used to maintain a comfortable temperature, liquid fueled heaters should not be used, as these generate condensation that can get into the paint. Before painting, the surface was cleaned with a tack rag – a sticky piece of cloth that is effective in picking up dust – to remove all dust.

The brush used was thoroughly cleaned, the bristles being well worked before use to identify and remove any loose ones. The size of brush chosen should be the biggest that can be handled, yet is able to get into any crevices around the engine casting, in this case 1-1/2 inches wide. The paint was poured into a small paint kettle to prevent any contamination of the main tin through foreign objects being picked up by the paintbrush.

When applying paint, it is important to work quickly; the brush holding almost too much paint so that it is applied easily yet not overloaded. The painting was done in small sections, brushing in both directions before moving to the next one, brushing back into the edge of the previous one. Maintaining a wet edge throughout meant a better finish. When painting, do not stop to look at your work until finished. Once covered, the paint was left to dry fully in accordance with the manufacturer’s instructions.

If a fly or other contaminants gets into the paint leave it alone until dry, then remove. If you have any paint runs or sags do not sand it. Instead, slice off the top with a razor blade, then leave to dry before sanding it and then repainting the area.

The first items to be painted were the fuel mixer and pipes. This was to give these parts the longest possible time for the paint to cure and minimize the risk of fuel attacking the paint.

The base casting was painted next so that the fuel tank could be fitted. As mentioned before, this had been painted black, but this paint was peeling so the tank was cleaned back to the galvanizing and then left unpainted. The base was then fitted to the new cart and then the main engine block lifted into position. The new cart made it easy to move the engine around when painting it. The underside of the engine block was painted before it was fitted. The painting of the engine and the various parts was not rushed, with plenty of time allowed for the paint to cure thoroughly and harden before any assembly.

The paint used dried fairly quickly, and a skin formed in a nearly full can almost overnight. The paint for the final coat was poured into a clean paint jar through a piece of mesh cut from a discarded pair of my wife’s tights to filter it. The paint was quickly applied and the workshop closed until the paint had dried to prevent any movement of dust.

When the painting was completed, the area of the cylinder head gasket was cleaned, as well as the seat for the tapered plug for the ignitor, to ensure a good airtight fit. New decals were obtained and were put in place after assembly.


When the engine was purchased the muffler consisted of a length of bare pipe pointing to the sky, connected to the cylinder head by a couple of elbows. The standard muffler is fairly simple, being made from sheet steel, so it would not be too difficult to make one. Photographs of several mufflers were examined showing the muffler to be little more than two pieces of sheet metal, one piece welded to a short section of threaded pipe and the other having a pressed dome.

Starting with the back plate, I found a disc of steel in the scrap bin that was 0.375 inches thick and 6 inches in diameter. Rather than form the back of the muffler from sheet steel, this part would be quickly turned on the lathe to create the required shape.

To make the domed front section, some 2mm-thick steel was cut to 7 inches in diameter, well over the size needed, but this gave plenty of room to hold it when forming the dome and when finished it could be easily trimmed to size.

To create the dome in the steel a short section of steam pipe 3 inches in diameter was used as the former. Steam pipe was used in view of its thick wall, making it more rigid. The inside of this pipe was chamfered to assist in getting a smooth dome.

With the steel laid on top of the former, the steel sheet was repeatedly tapped with a round head hammer, starting in the middle, moving the metal round on the former as it was being struck. This was repeated, gradually moving out towards the edge until the dome was formed. The dome was then adjusted by tapping in areas that were not raised enough until an even dome was formed.

The outer edge of the sheet was then cut to size and the dome planished to smooth out the marking in the steel. This was achieved by resting the inside of the dome on the smooth head of a cold steel chisel that was used as a stake. A hammer was used to lightly tap the outside at the same time as moving the dome around the stake. The face of the hammer was completely smooth, with no burrs to mark the dome.

After welding a short section of threaded pipe to the back, three holes were drilled through both this and the dome piece, then three rivets were fitted to hold the muffler together. A file was used to clean up any remaining marks.


After stripping the engine the crankshaft was examined. The crankshaft had some deep rust pitting, including the big-end journal, but the surface appeared fairly regular so there seemed little point in going to the expense of regrinding it.

One problem was the exposed areas of crankshaft that had been covered in red paint, and it proved difficult to remove this from the old rust pitting. A wire brush had little effect and even using a sharp metal prick left some paint showing.

To rectify the problem, the ends of the crankshaft were covered in a thick layer of silver metallic paint that was left to cure for several days. The crankshaft was then lightly sanded with emery cloth to remove the paint on the surface, leaving any red paint in the rust pits covered.

Cylinder head

The intake and exhaust valves were removed, using a spring compressor to collapse the strong exhaust valve spring. The seats for the inlet and exhaust valves were cleaned and the valves oiled and fitted. The inlet valve spring was badly rusted, but a similar spring with the same diameter wire and pitch was found in my spare parts bin. The diameter and shape were not identical, but as the spring was made from relatively thin wire it was possible to modify the spring, stretching it on a steel tapered former to nearer the same size and shape of the original. Both valves were fitted and the keepers with pins put in place. The inlet port was cleaned of debris and the butterfly valve refitted. With a new gasket, the head was ready for fitting to the engine block.


The governor assembly was stripped, cleaned and repainted. As the butterfly valve had been removed from the inlet port for cleaning, it was necessary to reset the butterfly crank arm in conjunction with the governor. Fitting both the governor and cylinder head, one of the governor weights was pulled out as far as it would go and a wedge put under it to hold it. The clamp screw on the arm was already loose, and the butterfly was closed and the crank set so that the governor rod was 0.0625 inches short of falling in the hole of the crank arm. The clamp screw was tightened and the remaining parts re-assembled.

The governor would be adjusted once the engine was running and its speed known. This would be achieved using the speed regulator, the knurled screw between the governor and the ignitor trip arm. The screw with the lock nut near the governor weights is used to steady the action of the governor. If there is too much tension, the governor will be slow to respond to a change in the load. If there is not enough tension, the engine will race. Again, adjustment would be made when the engine was running.

Ignitor trip

The hook part at the end of the ignitor trip had sheared off with the trip, already showing signs of earlier welded repairs with some welding to the area of the knife edge. This weld was soft and easily marked with a file, whereas the rest of the trip was hard and durable. In order to make a lasting repair that would not deteriorate with use, a piece of mild steel would be welded to the existing trip finger, filed to shape and then case hardened to give it a tough skin.

The broken part of the trip finger was ground to a knife edge, as was the replacement piece. After welding, the new piece was ground/filed to shape. To toughen the repair the soft steel and the earlier welded repair were heated red hot before dowsing in case-hardening compound. The compound was scraped off the original metal, as hardening an already hardened material could cause it to crack. The area was then heated red hot again before quenching in water. This exercise was repeated three times. The test to demonstrate the effectiveness of the hardening was to try and mark it with an old file. The file just skidded off the hardened areas.


It is easier to shim the big end bearing on the bench before assembly. The existing shims were made from a card-stock type material, but a couple had disintegrated or been damaged. These were replaced with new shims made from brass stock.

The engine cylinder was cleaned and lightly oiled before using a piston ring compressor to fit the piston. Care had to be taken to ensure that the piston rings sat clear of the stop pins. The old rings appeared to have enough spring to give good compression and were not replaced.

The crankshaft was then fitted in its bearings and the old board shims re-used, removing some shims to get a good running fit. The connecting rod was then connected and the flywheel for the non-gear side fitted with a temporary key so the engine could be turned over.

The drain plug for the fuel tank was inaccessible and needed an extension tube to move it clear of the engine body and cart rail. A barrel nipple could unscrew when removing the plug, so a tube was made with a hexagonal section at the end for the plug. This allows for a wrench to be used to hold the tube when unscrewing the plug.

Cam gear and timing

The cam gear should have two dots center-punched on the face of the teeth. The gear on the crankshaft should have one tooth marked with two dots and this tooth should fit between the two dots on the cam gear.

If the marks can’t be found then the engine should be timed so that the exhaust valve begins to open when the crankshaft is 30 degrees before outer dead center. (A rough setting can be obtained by putting the crank web pointing straight up and the nose of the cam also pointing straight up.) The exhaust valve should close when the crank is 5 degrees above inner dead center.

The ignitor should trip when the mark “spark” stamped on the face of the flywheel is level with the exhaust rod. The eccentric should be on the “E” position. In this case, the spark line was not visible on the face of the flywheel so the trip finger bracket was adjusted so that ignition took place 22.5 degrees before top dead center. To set this position a piece of tape was placed on the ignitor side flywheel, with a line marked at top dead center. The reference point for this line was the lug on the side of the governor. Another piece of tape was placed on the flywheel with another line to mark the 22.5 degrees. The position was calculated by piding the flywheel circumference (diameter of 22 inches x 22 pided by 7) by 16 (360 degrees pided by 22-1/2) giving 4.3 inches. With the ignitor set to the late position (L) ignition takes place after top dead center.

For the pushrod, there needs to be 0.0625 inches clearance between the end of the push rod and the adjusting screw for the valve rocker. The old spring was used, with the addition of a small spacer ring to ensure sufficient tension so that its roller always tracked the cam.

Completed engine and starting

Before starting, all nuts and bolts were checked for tightness and all oil and grease points lubricated. The drip-feed oiler was set to six drips a minute and left open, and some water added to the hopper.

The fuel reservoir was filled with gasoline after closing the overflow valve and using the lockout lever to hold the fuel pump lever out of action. The throttle valve was opened one turn and the ignition eccentric set to “L” for late. Pushing the inlet valve open, the engine was turned with the starting wrench to get it in motion. While still turning, the air inlet in the bottom of the reservoir was half closed with the fingers of the left hand but for only one revolution to stop flooding the engine.

The engine fired at the first attempt, but immediately cut out, and this was repeated. It soon became apparent that too much fuel was being drawn and opening the needle 1/2 turn allowed sufficient fuel to be drawn in. Once the engine fired, the trip finger eccentric was set to “early” and the fuel pump freed when the mixer reservoir was nearly empty. There then followed a period of adjustment to both the needle valve and governor to get a smooth-running engine, the speed being set slightly lower than the factory specification of 450rpm.

The engine was started on gasoline, with the fuel tank being filled with kerosene. Wherever possible kerosene is used as the running fuel as this negates any problems of gasoline destroying some paint finishes. Despite being advertised as “fuel resistant,” the paint used in this restoration bubbled as soon as a splash of gasoline hit it. Since gasoline is only being used for starting some alkylate petrol is now being used to stop further paint damage. This is three times the cost of gasoline, but a gallon lasts a long time and has no effect on paint. This fuel is also ideal for model engines.

This completed a fairly straightforward restoration, resulting in an engine that looks more in keeping with its history.

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