[sidevalve5]

Hi John,

It looks like you have fixed it. This is my experience of them.

Over the years have had several leaking Ewarts fuel taps. Did once get some replacement corks, but they were poor quality, still got leaks. Have tried PTFE tape, nitrile cord, soaking the original corks in an oil/paraffin mix. Nothing really worked. Have had a couple of taps where the threaded spindle with stop end had seized and then saw on ebay a chap from the USA selling an O ring kit. They worked really well, so I took the dimensions of them and then got some from a UK O ring supplier. They were FKM (Viton) Brown 75 ShA at 4.42mm ID and 2.62mm Cross Section. To fit use plenty of lube, fit 4, but if tight fit 3 and put in a small standard O ring to take up the gap. They have cured the leak on every tap I have fitted to them to, the operation is smooth as well. They cost pennies. But you have to get the correct sized O rings, or they may not work.

Best wishes,

Grahame

[sidevalve5]

‘You pays your money and takes your choice’ with mag testing. A ‘Proper’ test rig would be one that can rotate a magneto, be able to measure the voltage and current output of both the primary and secondary coils. Ideally be able to view the sine waves on an oscilloscope and check the spark gap in air with a 3 probe adjustable tester. For flywheel magnetos, similar except without a magnet passing over the coil, a current is supplied to the primary coil.

Without access to such equipment, only static testing can be carried out by measuring the resistance of the LT and HT circuits. This is carried out with a multimeter.

Condensers can be tested either with a megger or the capacitance function of the high quality multimeter. Have found a lot of ignition problems are caused by the condenser. As I do have a megger, I can test one. For those who do not have access to one, my recommendation if the LT and HT circuits seem OK, is to replace it. But I fit a modern polyester film capacitor with a Voltage Rating of 630v. Capacitance 220nF / 0.22uF. Can get 10off for £4.09p here https://www.ebay.co.uk/itm/301127883221?var=600476142172 I mount them on a small circuit board, but you may get away with a small piece of stiff plastic.

Testing a mag with multimeter is easy, it only takes a few minutes. If I find a fault in the coil, I replace it. If I still do not get a 6mm air gap spark, I replace the condenser with the capacitor above. For me, it’s worked every time. Although I there are some mags with a suboptimal windings on the coil and/or tired magnets. As yet, I have not had one. When I do I will trial again a single wire energy transfer coil system and get the magnets remagnetized.

[sidevalve5]

Hi David,

Great that with some more work you managed to get the carb to work well. From what I could see of the pictures you posted it looked like there were potential faults in the design. The float may have not moved freely up the central column, it could twist and then stick. How it pivoted against the needle meant it would not hit the needle square every time. Causing it to not operate as reliably as it should. But you have fixed it, brilliant.

Have often thought of fitting an aftermarket modern carb to an older engine. Was always concerned if I could fine tune it. You post rekindled my idea and after 5 minutes on the computer I found that there are a huge range of cheap carb jet kits available. May give it a go when I have time one day.

Fully concur with both your grandad and Andy about old stuff. If set up well, they are a joy to use. But if not, they are hard work to put it mildly. At times I used to hate using my Trusty until I got it sorted. Your tale of the MG6 putting your grandad up against a wall reminds me of hearing of someone killed by a Trusty. It put a chap using it through the side of a greenhouse, he died from blood loss. Find it really satisfying that often with a little tinkering, what some may regard as scrap can be used again. Operating in a smooth controlled manner.

Best wishes,

Grahame

[sidevalve5]

If you have not done it already, firstly I would remove the points, hone any pitting out from the contact surfaces, refit and set the gap to 0.015”, also clean all terminal connections. With the plug cap removed, hold the end of the HT lead 6mm from a clean part of the engine and see if there is a spark. If there is, you have fixed it, if not, close the gap until its 4mm away. I find holding the HT lead steady difficult, so have got an adjustable spark gap tester that was <£4, its one of the best tools in my box. An engine will start and run with a 4mm gap, but for easier starting and smoother tickover, you really need the gap to be 6mm. A good mag will achieve this. <4mm and the mag needs attention and personally I am not happy until I get it to spark at 6mm. If still there is a poor or no spark, a test with a multimeter is as follows: for LT Continuity, rotate until the contact-breaker points are open. Set the dial to 200Ω, measure the resistance with the two probes shorted together. The reading will probably be a fraction of an ohm and note it. Then measure the resistance between ground and the ‘hot’ side of the contact-breaker. Deduct the noted reading from the reading on the dial and the result should be between 0.5 & 0.7 Ω. A high reading indicates a bad connection or break in the low-tension circuit. A lower reading means there is probably a short-circuit in the contact-breaker assembly or in the armature. For HT Continuity, set the dial to 20KΩ, place the red probe on the pick-up or HT lead, the black to ground, the reading should be between 3 & 7 KΩ. If significantly higher there is probably a break in the HT winding, or a bad connection between the winding and the pick-up. If significantly lower, its unusual, but still indicates a problem. A lot of ignition troubles are due to the condenser. If the LT and HT tests are fine and you have access to a megger, the condenser should pass a 2GΩ @ 500v test. If you cannot do such a test, I would replace it with either a recently manufactured one, not NOS and certainly not second hand. As the wax paper inside them deteriorates with age and use. Or get a modern capacitor such as an EasyCap CU220 from https://brightsparkmagnetos.com/ which is my preference. In my experience they often perform better than old style condensers. Have had instances where a good mag with the existing condenser achieved a spark at 4mm, by fitting a modern capacitor the gap increased to 6mm with the subsequent easier starting and a smoother tickover. Resting a plug on the side of an engine to see if there is a spark is not a good enough test if ignition problems are suspected.

The above is the test procedure for a home mechanic who can use a multimeter. A multimeter will not test the condenser though. Others may advise you go straight to a specialist who may or may not have dedicated equipment. My advice if you are tempted to go down this route is to firstly get a quote, even testing will cost a fair bit. The above is free if you have a multimeter, about £8 – £12 if you have to purchase one. But it will be an investment as it has many uses.

[sidevalve5]

Hi David,

Have thought several times of fitting a modern carb to an industrial engine. Bought a cheap Chinese copy for a Honda for around £12 and was amazed of the quality and how they could sell it for that amount. Am not a fan of some older type carburettors, they are quite crude in comparison to more modern versions. The float/needle arrangement and the method (if any) of emulsifying the fuel is often poor. Could you send some pictures of the manifold and throttle linkage arrangement and I will try to think of what replacement carb may be suitable.

Off now to get a nearly new Locin 1” pump for £40. The Villiers/Alcon will be sat in the shed for a while yet I think.

Best wishes,

Grahame

[sidevalve5]

Dear David,

Fantastic descriptions and pictures of your precision engineering skills. You remind me of an old boy who does a few little jobs for me. He has made scale stationary, steam and aircraft engines from scratch. What he can do amazes me and he is in his eighties.

Without those abilities people like me have to try to work with what we can obtain. I had the problem of getting hold of some piston rings for a Gravely D. No chance as named spares, but whilst researching fell upon Hastings Piston Rings. After reading their very helpful technical guidance, found a set that fitted in their brochure. Although they were an American company, they had a franchised distributor in the UK. So ordered them. They could have also supplied some for a Jap 5, but in the end as Cox & Turner had them in stock. Purchased some from them.

Was told once Ford Consul pistons would fit a Jap 5. This was not true, but after the success with the rings I tried to do the same with specialist piston suppliers. Was hoping to find a way of getting a replacement piston when it was not obtainable as a named spare part any more. But have drawn a blank. I cannot find on the internet a catalogue where I can cross reference: bore, gudgeon pin diameter, compression height and crown profile. Does anyone know of a method of doing this. Where it may help David, or anyone else, is to obtain nominally obsolete pistons to keep their old engines running in good order.

My elderly engineering friend has a large and rare oil engine with the plug, or more like a pair of electrodes, sitting in a chamber outside the cylinder. It’s a lot cruder than the Rover one shown in your pictures. As for the carb, I would just fit a modern one if parts are no longer available. As I think some of the older types were just too rudimentary and unless in good condition, cause a lot of problems. But I am more interested in performance than originality. Others may take a different view and can well understand that.

Best wishes,

Grahame

[sidevalve5]

Hi William,

Am presuming the mower has a Briggs & Stratton engine. If so, I have found they sometimes need fine tuning with the mixture screw to run well. Have a 12HP model on a Ransomes Bobcat mower and even 1/8th of a turn on the screw can make a big difference. Do not think a normal compression tester is the best tool to use on hand start single cylinder petrol engines. They really operate best when the engine is running at least electric starter speed. The correct tester is a leak down type. But if you do not have access to one and I do not. I use the thin latex glove method. Fit the glove tightly over the exhaust and bring the engine onto compression. If it rapidly inflates, its the exhaust valve leaking. Do the same test over the carb inlet and if possible over the oil filler hole. This will test for blowing past the rings. The glove will inflate a bit, but if it rapidly does so, it identifies the problem area. You valve clearances seem a bit small to me. Would check the manufacturer’s recommendations.

Best wishes,

Grahame

[sidevalve5]

Hi David,

My Villiers engined Alcon pump is definitely 1½”. It does have a model number on it. I got it from a retiring market gardener, who sold me all the delivery and suction hoses too. It ran poorly, so I did my usual top end, points and carb service, it then ran well. It was noisy though under load and drank fuel. The Honda GX160 is a lot quieter and less thirsty, the Robin EY15 even better on both counts. The pumps have a superior performance than the Alcon too. So am on no particular rush to get the Villiers/Alcon combi running again. Very interested to hear that the pressure gauge had a red line at 20 psi and it rarely achieved that. It explains a lot. A friend of mine got 16 spraylines (they are each 15’ long) with a Villiers/Alcon combi and it never worked very well. He said he then got a Honda pump that ran the spraylines fine. He grew lettuce, watering regularly. He filled the fuel tank full and left it to run dry whilst he went off to do another job.

When I first took the Alcon pump apart, found the seal had all but disintegrated. Vulcan Water Seals were very helpful in identifying a replacement and were keen for it to be added to their database. The Clark pump had been purchased by a chap who had had his house flooded and wanted it in case it happened again. He then moved house and had no further use for it. He started the engine every few months, but did not know he was meant to put a bit of water in it to keep the seal lubricated. When I came to swap the pumps over I could see the damage done, so put a new seal in, again from Vulcan. Just for the fun of it I tested the suction with a vacuum gauge. This is when I found the Alcon pump was not achieving the recommended 20-25 ins Hg negative pressure. The others passed.

Had an idea to increase pressure by pumping from one pump, through another to replicate a multistage pump. But it did not work, the second pump was the Alcon and the Villiers engine struggled with the flow rate from the Clark pump. I did get an increase in pressure, but it was not enough. Quickly realized a multistage pump needs to have a calibrated flow from the first stage to the second and maybe a different impeller design too. My effort was doomed to failure.

Best wishes,

Grahame

[sidevalve5]

Hi David,

Have a 1½” Alcon pump powered by the Villiers engine. Got it in the 1980’s and used it for irrigation. But then got sprinker rotor heads that needed a higher pressure (30 – 35 psi) than my original ones. The pump also started to take an age to prime. Fitted a new seal kit I got from Vulcan Water Pump Seals, it improved the suction, but still the pressure was not sufficient. Got another Honda engined Clark pump (26 meter head), but still the pressure was not enough. So did try to link the two together, but I only got a small increase in pressure. In the end got a Robin engine Koshin pump (30+ meter head), it performed well.

Took the Alcon pump apart again and found the engine crankshaft was pitted with rust. I think these indents allow a small amount of air to get past the seal and effect the pump’s performance. I was going to go along a similar line to yourself and sleeve the crankshaft. But without your skills I was going to use a hardened stainless steel shaft repair sleeve. Proposed to fit it over the shaft then grind off the flange. What do you think of that idea.

Decided I would swap the Koshin pump and fit it on the nearly new Honda engine, the Clark pump onto the well used Robin engine. Found that the crankshaft on the Robin engine had grooves on it where the seal was in contact with it. Also the Clark pump seal was not in the best condition, so replaced it with one from Vulcan. Now have two pumps that perform well, although the Koshin is the superior one.

Dropped on some Evenshower Oscillating Spraylines and these operate at a much reduced pressure. In fact I now use the Clark pump and only need half revs from the Robin engine. The original pendulum operated oscillation valve was worn out and leaked everywhere. So make another from a pair of ¼” ballvalves. But the operation was too stiff for the pendulum, freeing them up caused leaks. Have just spent Easter Sunday making a new valve with a 3 port L configuration. Have high hopes of success and will be starting irrigation this week. It needs it too, in my part of the world near Evesham we have not have any significant rain for 6 weeks or more. Am going to put a pressure gauge on the irrigation system to see exactly what pressure the spraylines need. They are very satisfying to see operating, gently and quietly going from one side to the other in true 1950 – 60’s market gardening style.

Best wishes,

Grahame

[sidevalve5]

Hi Will,

Many thanks for that. Cox and Turner is one of the suppliers I have for parts and they are usually my first port of call for engine spares. Can get rings a bit cheaper from a manufacturer, but prefer to use Cox and Turner because they are fellow enthusiasts.

Have fitted new rings and ground in the valves on many engines. But some I have worked on have been left stood for years in damp conditions. The valve contact surfaces and the seats have become very pitted with corrosion. Managed to lap most of them out, but the contact surfaces widened, ridges and grooves formed too. Got good compression to start with, but after some hours work it tailed off. Put a thin rubber glove over the exhaust and the carb inlet, it blew up when the engine was near the end of the compression stroke. Am going to get the valve seats cut and the valves themselves re-faced. But as the contact surfaces are now so wide, am going for a 3 angle cut. When I have it done will post something on the forum to share my experience. If anyone has had this done, would like to know what they thought of the results.

Best wishes,

Grahame

[sidevalve5]

Hi Will,

Did not see your posts until this morning. I set the tappet clearances on a Jap 5 & 6 to 10 thou on the inlet and 20 thou on the exhaust. These figures are stamped on the inside of the inspection cover. Have also fitted new rings if required and can vouch for the increase in compression when this is done. Have two Douglas SV54 engines that I got when I purchased a couple of Trusty’s that were taken apart so that they could be stored. Intend to reassemble the machines one day and will make sure the engines perform well. If they need new rings, I will fit them. Out of interest, where did you get the rings from.

Best wishes,

Grahame

[sidevalve5]

Hi Dave,

Many thanks for the post. Just to clear up one point about ignition systems on small engines and tractors. They all work along the same principle with a current flowing through the primary windings of the coil generating a magnetic field. Which in turn saturate the secondary windings with lines of magnetic force. When the current flowing through the primary is interrupted, the magnetic field rapidly collapses, which cuts through the secondary, generating a very high voltage which seeks a path to ground. This arcs through the spark plug electrode gap, producing the spark that ignites the fuel/air mixture.

Obviously the higher the low tension voltage in the primary, the greater high tension one is generated in the secondary, thus a bigger spark. With a points/condenser system, just as the points open, the current that was flowing through them seeks a path to ground. The primary coil has a degree of resistance which prevents this. During the opening sequence, the points have a tiny gap and the current can arc and go to ground through that, its an easier path than through the primary windings. The purpose of the condenser (a capacitor in all but name) is to take the current away from the points as they open and store the electrons until the points close again when the current will then flow though the primary. The capacitor has two functions, to prevent arcing at the points and to store electrons so they can be used to boost the current when the points close. More current though the primary and the speed at which the current is stopped from flowing through the primary increases the rapidity of the collapse of the magnetic field which generates a higher voltage in the secondary. The condenser is a vital part of the points system and one that is often over looked when a service or overhaul is carried out. I know this to my cost, wish I had studied ignition systems in more detail when I was younger. I got to the level of understanding the principles, but not how the different components operated in unison and the actions of each upon the others. Could have saved hours of trying to start motorcycles, garden tractors and mowers. Have found from experience and research small engines need a 6mm air gap spark to operate well. Under cylinder compression conditions, it is harder for the HT current to pass a gap. So for it to pass say a 0.025” gap consistently and with sufficient intensity under pressure, a 6mm air spark gap is a reasonable equivalent. A spark from a plug resting on ground is no test at all.

In the Kettering system the primary is supplied with a permanent low tension current from a battery. With magnetos, the current is supplied when the magnet passes close to coil of copper wire wrapped around a soft iron core. Lines of magnetic force that go in one direction are produced in the iron core as the north end of the magnet passes over it. These lines change direction when the south end passes over. The point at which the lines of force change direction is called flux reversal and in that instant a voltage spike occurs in the primary and it is when the points open. In the transistorized module you have mentioned, there is a sensor that ‘sees’ the flux reversal, the sensor operates the transistor, which is in simple terms is a switch, just like the points are. Current is stopped from flowing to the primary. The big advantage of the transistorized system over the points/condenser type is the time it takes to stop the current flowing through the primary is almost instant and complete. The collapse in the magnetic field is more rapid, the voltage generated in the secondary higher. With points there is some milliseconds where the current is going to ground through the contact surfaces just as they part, even with a good capacitor. The collapse in the magnetic field is not as rapid.

Have had an 8mm air gap spark from a transistorized module and modern engines are generally easier starters than the old stuff us silly buggers mess about with. But have found as long as a spark of 6mm is obtained with the lower state of tune of an industrial engine, it is perfectly adequate.

To stop interference to TV’s there is a resistor in most plug caps. If you had a very weak spark, you may use a non resistor type. But have found if I achieve a 6mm spark, the resistor type is OK.

If you still want to do a Kettering system, think you will need a two wire 6v ignition coil. In the UK they are available on ebay as cheap as chips, presume its the same in France. Personally if the replacement flywheel is the same as the original, I would still get the hub off and take it from there. Would not be keen on using the machine without fan cooling and the affect of the flywheel inertia. If the coil tested good, would fit a Meco unit. Maybe if the coil was duff, I could contemplate a total loss battery system. The faff of the limitations of the battery would put me off. Much prefer to get it out of the shed, check the fuel, turn it on, choke, tickle, a pull on the rope and off she goes.

Phew, hope I have explained everything in terms you may understand. Expect an electronic engineer would do a better job than me at it. Off now to continue working on a nearly new MacAllister strimmer that is very hard to start because it has a 4mm spark. It is a piece of Chinese plastic crap, but have managed to get the coil off. Got to see if I can get an after-market replacement. Am a big fan of transistorized ignition, but have found a few that underperform. Am not sure if the vibration and heat generated by a small engine damages the circuit components over time. I have no way of testing them, so its just a replacement job.

Grahame

[sidevalve5]

Andy, fully concur, if all the components in a magneto coil, points, condenser set up are good. Then so is the spark. Angus Shapland concluded that a Meco transistorized unit was not superior to a good points system. He liked them because it got rid of the condenser and after he had serviced a machine with points for a customer. It was then laid up for a while in damp conditions and when brought out again, would not start. The customer moaned, but he found all that was wrong was corrosion on the points. The Meco unit eliminated that problem, it was ‘fit and forget’. Have a Gravely L with a Bosch mag, a Trusty with a Jap 6 with a Wipac CJ mag and a Hayter Condor with a Kohler K181 with a flywheel mag. To all three, after a light hone of the points and resetting achieved a spark at 6mm. Left the original condensers in place and they all started easily and tickover is smooth. As an experiment I replaced the condenser on both the Gravely and the Kohler with a polyester film capacitors, there was no improvement. But I also have engines that could not attain a spark at 6mm, but would at 4mm. The coil tested fine, the points were clean and set up correctly. Starting was difficult and tickover erratic. This was especially a problem with manoeuvring a Trusty in tight spaces. The mags were Wico Series A’s, spark was 4mm, one had a condensor that failed a megger 500v test of a 200M ohms requirement, the other passed it. Fitted capacitors and both mags sparked at a 6mm gap. The improvement in the overall machine’s performance was remarkable. Have had transistorized ignition modules on engines that are difficult to start. The spark gap was 4mm or less, even though the coil passed a manufacturer resistance test. I replaced the module with cheap non-OEM ones and the spark exceeded 6mm, the engine was fixed. But I digress (hugely).

Back to David’s flywheel and I have another idea. If the hub HAS to come off, try using a 4” thin blade on a disc cutter with a longitudinal cut. From the replacement flywheel calculate the depth of cut that would be just touching the crank at any given point on the hub. Where the radius of the disc limits the cut near the armature plate, drill 1/8” holes at ¼” centres, then enlarge them with a ¼” bit. With feeler gauges measure the gap in the cut, put some steel wedges (chisels or screwdrivers) in the cut and tap tight. Measure the cut gap again to see if its parting. Try to remove the hub with a puller, if this initially fails, apply some heat to the hub. Still no go, do a similar cut on the opposite side of the hub. If that still fails, go down the pub to drown your sorrows and curse the time you ever contemplated messing around with a knackered old piece of machinery. If its any consolation, I’ve been there many times.

Grahame

[sidevalve5]

Thanks Andy, I did not know that. Have never worked on the close cousins of the Mk 25c. Have become a bit anal about magneto ignition. For years I subscribed to a school of thought that if engine had compression, fuel and a spark from a plug resting on ground. It should go. If the spark was blue and fat, as opposed to weak and yellow, all the better. But after reading technical information from Brightsparks, speaking to the owner and trying one of their capacitors. I realized that not only was the plug spark test no real test at all. But how an apparently good magneto could be greatly improved with a top performing condenser, or a modern capacitor. I now have a golden rule that if I cannot get a 6mm air gap spark, I work on the ignition system until I do. The difference in engine starting and tickover between a 4mm air gap and 6mm one is remarkable.

[sidevalve5]

Wish to correct and clarify what I posted yesterday about changing a magneto flywheel. I said it was just the cam lobe and magnet position that was important. Upon reflection, this was misleading, there are other factors too. Including: coil position on the armature plate, magnet to coil air gap and points cam feet position. Everything has to operate in complete synchrony for a good spark to occur at the correct time for the engine.

If the part number is the same on different Villiers model’s flywheel, then they should be interchangeable. But if the part number is not the same, then there is a risk it will not work, or even fit. Of course none of this will matter if David is going to use the Kettering ignition system. As long as the points open at the correct time for the engine. At a push, could even get away with not using the flywheel rim. Modern two stroke motorcycles do not have them. But the engine will sound like a motocrosser when in work and is more likely to stall.

Am going to see if my potentiometer is going to work at the weekend. Have a 14.4v drill battery that is reading 18v. If its successful, will post it, because it will be an easy and cheap way of powering a total loss battery system. Most folks have a battery drill and charger.

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