General Technical Help
This section contains pages and links to technical information that may be useful when undertaking restoration and preservation projects. Some of the content was created by The Old Lawnmower Club and some of it is in the form of links to other sites.
General Hand Mower Advice
Hand mower components such as T handles and rear rollers for sidewheel mowers and hand grips and front rollers for roller mowers were often made of wood. These inevitably disappear over time through damage, rot or wood worm and replacing them with original parts can be almost impossible. We generally recommend asking a local woodturner or hobbyist to make up new parts using what remains of the old ones as a pattern. There is usually someone in most towns who knows how to use a lathe and they are often only too happy to help with this sort of thing. To find them, ask in the local ironmongers or wood yard as they are likely to be known there. Yellow pages is also a good place to look. When you have found someone, ask them to use ash, beech or elm for the greatest authenticity. As a guide, hand-grips on Greens roller mowers were normally of beech, but Ransomes used ash up to the late 1930s, when they too started using beech. T-handles on side-wheel mowers made in the UK were usually ash up to the 1930s, when beech came in. American side-wheel mowers often have maple handles, though Pennsylvania handles (UK and US) are usually ash.
Grass Boxes
Grass boxes inevitably go missing or simply disappear before your eyes due to rust and rot. In fact, many side-wheel mowers may never have had a box in the first place as it was normally an "optional extra" for these machines. As might be expected, finding a replacement box is virtually impossible. It is occasionally possible to find spare boxes at car boot sales, junk shops and especially at mower repairers but the chances of matching the right box for a particular mower are slim. Boxes for mowers such as the Ransomes Ajax, Webb models from the 1950s and a few other machines can still be found in this way with a bit of persistence.
For all other mowers there is no simple answer as making one from scratch is often beyond the capabilities of most enthusiasts and the cost of asking a professional engineer or carpenter to do the work can be prohibitive. However, anyone with the right skills should be able to copy an existing box using the original as a pattern or basic dimensions supplied by another enthusiast. Early boxes can be relatively easy to fabricate because they had simple wooden sides with the box formed by a thin sheet of steel. The box mounted on the mower by simple brackets that can often be easily copied (if those from the original are no longer available) and made from steel or aluminium rather than cast iron. Once painted nobody would be able to tell the difference.
Block Chain
The original block chain used on many hand mowers before 1914 cannot be supplied and we know of no current source. The only way to replace a missing or broken chain is to use a redundant length from an old "donor" machine.
Cast Iron Components
Most early mowers were made using cast iron components. While original replacements for these are no longer available copies can be made using modern castings. Although decreasing in number there are still many small iron foundries around the country that can make castings in small numbers to order using originals as a pattern. Members of The Old Lawnmower Club have, over the years, managed to obtain items such as chain sprockets, gears, gear covers, handles and grass box handles/brackets made in this way. It is sometimes possible, and usually cheaper, to make the casting from aluminium rather than iron and there are more foundries that can offer this service. An alternative method is to machine a copy using steel or aluminium.
General Motor Mower Advice
Type Of Petrol
One of the commonest queries to the club is about the correct type of petrol to use with a vintage lawn mower. Although many old motor mowers with four stroke engines were made during the period when leaded petrol was standard the prevailing view is that these machines will run perfectly well on ordinary modern unleaded fuels. Lead based additives were used in petrol to help lubricate valves and prevent preignition on four stroke engines. However, old mower engines do not generally run fast enough, hot enough or at sufficient compression ratios for the presence of an additive to be a major factor. Two stroke engines do not require leaded fuel or additives.
Smaller and faster running engines made after about 1970 may benefit from use of an additive. Local mower repair shops will be able to advise customers on mowers with this type of engine which falls outside the scope of the Old Lawnmower Club.
Spark Plugs
Many older motor mowers require 18mm spark plugs that are no longer available. Some specialist vintage engine part suppliers may be able to assist.
A useful source that cross-references some old spark plug number with the modern equivalent can be found here.
Villiers Magneto Rebuild
These simplified instructions are intended as a guide for anyone attempting to strip down and repair a similar ignition system. The Atco mower which was being serviced was the Deluxe model from the 1930s although the same engine was used on many of the company's earlier models from the 1920s as well as later machines up to 1939 and after.
It is advisable to have a set of Whitworth combination spanners available. These are a huge benefit compared with using a “close match” metric or standard Imperial spanner. The use of adjustable spanners is particularly unsuitable when having to apply the rather large torques for removing or re-fitting the flywheel.
1: Ignition System Access
Gain access to the ignition system by prising off the aluminium casing from the side of the engine. This will reveal a heavy brass flywheel with access holes for checking points.
The contact breaker points are housed beneath the brass cap (see image) whose retaining arm must be swung sideways to open the cap. With a little careful manoeuvring, the cap can be removed through the access holes in the flywheel and the points gap can be checked and adjusted. The gap should be checked (probably 0.015”) and adjusted using the threaded adjuster and locknut as required.
2: Removing The Flywheel
To perform any maintenance on the ignition system other than cleaning or adjusting the points, it is necessary to remove the flywheel. This is best achieved by jamming the flywheel (to prevent its rotation) with a wooden wedge between its outer circumference and a mower cross bar.
Then, using an appropriate ring spanner, give a sharp strike to the ring spanner with a hammer in an anticlockwise direction to shock the nut undone (see image). A 1/2in Whitworth ring spanner can be used however, if one can be found, Villiers also produced a special spanner (called a Hammertite spanner) for this specific task. This has a ring spanner at one and a place to hit with a hammer at the other.
If successful, the nut will undo by about one or two full turns before apparently locking-up again. You need to shock this anticlockwise again which will then prise the conical flywheel mount from the mating taper on the crankshaft; the nut is captive but rotates within the flywheel.
The magneto flywheel contains a pair of permanent magnets and the original Villiers maintenance advice was to place a piece of iron (e.g. a spanner) to bridge across the poles thus preventing loss of magnetic flux.
3: Removing The Armature Back Plate
To inspect or service the ignition system, it is easiest to remove the whole magneto assembly from the engine. Disconnect the H-T lead from the spark plug. Loosen the set screw which is behind the armature back plate and which clamps the back plate on to the engine’s crank housing.
The back plate is also clamped to the crank housing with a support bracket. On some Villiers ignition system, there is an alternative clamping arrangement allowing some rotation of the back plate so as to “tune” the ignition timing.
With a bit of back-and-forth rotation of the back plate around the axis of the crankshaft, the entire armature back plate should come away from the engine (see image) and can be overhauled more easily on a well-lit and clean workbench (to avoid losing small but crucial parts).
4: Checking or Replacing The Ignition Coil
If the engine is suffering from a weak (or no) spark, then the problem may be within the magneto coil. This can be checked using a voltmeter (to measure resistance) but it is required to remove the wire connection between the coil and the points.
The primary winding should have a resistance of just a few Ohms (measured between ground - either end of the iron core - and the socket in to which the points wire was screwed.) The secondary winding resistance should be 3-5k Ohms and this can be measured between the side terminal connection to the H-T lead and ground.
The most likely scenario with an old magneto coil is that it has some internal corrosion and the secondary winding (which is wound from extremely fine copper wire) has broken.
The coil can be removed from the “shoe” shaped laminated metal core ends by removing the nuts on the rear side of the back plate. You may need to use a screwdriver to counteract the torque on the corresponding screws which hold these core ends on to the back plate (see image). The core ends will then lift from the back plate and the coil can be pulled free from these shoes.
Replacement coils can be sourced via the internet but ensure that you specify the correct length and end diameters as there are various models available. Replacements are not cheap (perhaps £50) and beware of untested items for sale on auction sites!
With the flywheel removed, you now have excellent access to the contact breaker points and can provide a proper inspection.
5: Contact Breaker Points Maintenance
Disassemble the points by removing the contact breaker arm. This is held in position by a clip and spring. Note that the spring may easily be dropped on the floor – hence the need for a clean, well-lit work surface.
Loosen and remove the two screws which hold down the brass strip and which also clamp the low tension wire and the connection to the condenser. This brass strip is isolated from ground by insulating posts which should be inspected for cracks or other degradation. Note the order of construction of these components so that it can be rebuilt easily.
With the upper components removed, the base of the points housing can be unscrewed from the back plate and the capacitance of the condenser can be measured. The condenser rarely fails.
Reassembly is generally the reverse of the disassembly instructions above, but pay particular attention to the cleanliness of the contact breaker points. Even a thin film of oil from dirty feeler gauges can foul the points surfaces sufficiently to prevent a good spark.
6: Inspecting The H-T cable
Inspect the H-T cable for continuity between the spring-loaded coil end and the spark plug connection end.
Check also for cracks in the cable insulation. Replacement cables can be sought from the internet, but repairs can also be made to cracked or otherwise damaged H-T leads using appropriately-sized adhesive heatshrink.
7: Re-fitting The Flywheel & Final Set-up
Hold the contact breaker arm open while refitting the flywheel on to its tapered shaft. There are timing marks on the flywheel which should be aligned with the notch on the crankshaft end. This will ensure correct spark timing.
The flywheel nut will need to be tightened sufficiently to prevent any movement on the tapered shaft. If it is slightly loose, the flywheel may slip following a misfire, the timing will be compromised and the engine will run either roughly or not at all. Therefore, tighten the flywheel using the ring spanner and hammer arrangement previous described for removal, but this time for tightening (clockwise).
Finally, re-set the contact breaker points gap.
Check for a spark by unscrewing the spark plug, attaching the H-T lead and resting the threads of the plug against the surface of the cylinder’s cooling fins.
Villiers Two Stroke Engine Timing
There's a useful explanation of how to time a Villiers two stroke engine here.