[sidevalve5]

Hi Andy,

You are bang on saying that proper magneto testing equipment is rare nowadays and I expect it will be only produced in very small quantities, possibly only with an order, by specialist electronic equipment manufacturers. It will therefore almost bound to cost a fortune. Which is one of the reasons why it costs so much money to get a magneto repaired. The sections about testing in my first post were not my own words, but an amalgamation of information published by magneto repairer’s advice pages. It was they that mentioned the testing methods using a multimeter. I will readily admit not to having the knowledge and experience to advise on the matter myself.

Only know too well how frustrating it can be to have an otherwise good machine that is hard to start, or even will not go because of a poor spark. As a kid I was told to test for the spark by laying the plug next to a ground and turning the engine over. If it sparked it was OK and followed that advice for many years. But as George has said, it is not a sufficient test by any means. It is the intensity of the spark that matters. The advice from the specialists was that for magnetos on small engines with points, the spark in air needs to be 6mm minimum. Years ago, before I even knew this I purchased a spark tester similar to this https://www.ebay.co.uk/itm/285930250926 and have found it really useful. The better ones have 3 points, Briggs & Stratton produce one for just over £30, but its non-adjustable. So I think it has limited use. Stihl do a Oppama copy that is adjustable for around £60. A fantastic bit of kit, but its quite an investment for the occasional user. Was told you could make one with a timber base, with brackets that would retain bolts with the ends turned to a point.

I wrote the first post for my advice for those who do not have access to someone with specialist very accurate equipment. Or for others do not wish to spend a great deal of money on getting a repair done. So they may be able to do it themselves if they are willing to give it a try. In summary, if you engine does not start or runs poorly due to a suspected faulty magneto, firstly test to see if you have a spark through 6mm of air. If you have, the mag is almost certainly fine. If you do not, then proceed the further testing until you find the fault.

The area where I think we should on friendly and respectful terms agree to disagree is the use of a multimeter. Where I fully and wholeheartedly agree with you is that they should not be used just to test if there is a circuit, or continuity on a mag. A straight forward yes or no. It is the resistance within the circuit that matters. In the case of the low tension side, 0.5 – 0.7 ohm, the high tension element 3000-7000 ohms, unless a manufacturer specify differently. Would agree that the cheap digital multimeters may have some questions over their accuracy. But at less than £8, think they are a valuable addition to any tool kit. I have had one all my working life for testing 6v & 12v circuits on cars and motorcycles. Continuity and voltage on 240v and 415v AC circuits. But would not recommend a DIYer using one on a live mains circuit unless they know what they are doing.

Have successfully repaired and/or improved many magnetos, often with just a good clean and setting of the points. But if there is not a 6mm spark gap, I look to see the reason why and by using the methods in my first post. Have fixed the problem with my limited mechanical and electronic skills. George is correct again about HT coils. The old ones had shellac as the wire insulator and over time this fails. A test with a multimeter will find this out and if its not within the resistance range, order one from George like I have done. Believe the top end mag repairers have oscilloscopes to test coils under load. But thats way over my head. All I wish to do is offer some advice from my own experience of magneto ignition systems, their testing, repair and upgrading for a chap who wants to get his machine working sweetly.

The big improvement I wish to emphasise is the replacement of a traditional condenser with a modern capacitor (don’t let George know). The top end mag repairers do this for every instrument that comes into their workshop. Can vouch from my own experience, it improves the spark on a mag that has the correct LT and HT resistance figures. Its not the spark that is the big difference in practical terms though, but the significant improvement in hand starting and tickover. A 90 year old market gardener once said to me regarding his Merry Tiller. “If it does not go third pull, it goes back into the shed”. Am not quite at that stage just yet, but pulling on a starting strap, or even swinging a handle does make me blow a bit now after a few goes. If you are in the same boat, test your spark.

Grahame

[sidevalve5]

Hi Andy,

Firstly, none of the multimeter test figures came out of my head. I certainly do not have the expertise to recommend them. A lot came from published material from magneto repair specialists that I have collated and used very successfully on several instruments. I fully agree with you that just finding continuity with multimeter through a coil is not a real test at all. It is the amount of resistance that is important and different coils do indeed have specified different resistance requirements. It is why some manufacturers have published the resistance figures so a coil can be tested with a multimeter by a service engineer.

Have only this last week received some spares from George of Villiersparts, have used him many times. Following your comments I took the time to read what he said on his website’s Ignition page. I contend he actually confirms what I have said and indeed you too. I quote him “If you test one with a multi meter & find a circuit through the windings it still doesn’t mean it will function properly”. He does not mention resistance figures. Do have a lot of time for George, he has helped me out many times with difficult to obtain spares and indeed supplied me with one of his non original cheaper coils for the Villiers engine on the Clifford. It worked an absolute treat.

I wrote my piece in order to help other enthusiasts check, service, repair and improve a magneto themselves at a reasonable cost. The machines we are interested in are not worth a great deal of money, so if they can be kept going with little spent on them, then surely that is to the good. You appear to suggest the only way to properly test a magneto is by using a specialist ignition tester. Am presuming you are referring to a spark test being done under air pressure. A chap working on a vintage pedestrian machine may not want the expense of purchasing one. If such a fellow does not have a multimeter, then one can be obtained for less than £10. Taking a magneto to a specialist will cost a great deal of money, around £300 would be the approximate average. That is prohibitive as a lot of the machines they are fitted to are not worth that as restored runners.

Am very respectful of your vast experience, its very much more than mine. Would really like you to state what is your recommendations for someone with limited skill and budget when they have no, or little spark from their magneto.

Best wishes,

Grahame

[sidevalve5]

Thanks Andy. Well know I was done over with the cleaning. I asked my garage if they had a ultrasonic cleaner, but they did not, but said a neighbour did. So used him. Later chatted with a mechanic from my garage and they said he was not up to much and struggled for work. But thats yesterdays news and have moved on. Have a storage facility where there are a multitude of small businesses, we all help each other out. If I get a cleaner, can lone it to others and would hope to get expert help in return. Have looked at a 3.2ltr model for £80. Although was turned over with the cleaning, it did really get into the gum on the Walbro carb and made an otherwise blocked emulsion tube clear. The chap said he did 2 cycles and think if after the 1st he did a bit of manual cleaning of the jets, orifices and blind holes. Even if it was just to loosen some white corrosion deposits, he would have made a better job. Since then have bought a set of carb jet cleaning brushes and wires for £3.88p. Thanks to your good advice I do have a smooth running Gem and Trusty. Or did do, until the failing wheel gearbox went crunch. Buts thats part of the fun, getting a problem and fixing it. I do enjoy it and have the land to use the machines.

[sidevalve5]

Just noticed the image of the old friction plate could not upload because the file size was too large. Have reduced it

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[sidevalve5]

An update about the Gem. Found a chap with an ultrasonic cleaner who runs a garage specializing in vehicle electrics. Took a two Zenith 2T4 carbs, the Walbro carb and the petrol tap to him. He said the proper cleaning fluid is expensive, so uses dishwasher tablets and guitar strings to clean the jets. Went back to collect, the items were a lot cleaner, but the baked on carbon was not removed. Was told by someone else this method does not remove it. The Zenith carbs were dull, the Walbro bright and cleaner. He wanted £30-£40, gave him £30 cash. When I inspected the parts I could see he had not put anything through the jets and small orifices. A layer of carbon was still present, there were detergent marks on the surfaces. Had to give then another clean with petrol, then blow with compressed air. Managed to get some wire down behind the Zenith main jet and wiggle it about. Think this removed some white deposits sat there.

The good bit was the carbs perform much better. The Walbro had gum deposits blocking the emulsion tube, the Zenith on the Trusty had a seized main jet, so cleaning behind it helped the fuel rise more easily to the ventri. Overall very pleased, but did feel a bit done over by the garage. Think I may have to do as suggested and get my own cleaner. From research need one to heat to 80oC to remove oil and petrol deposits. A bit loath to have to invest in £100 for something I may use once a year. Have a steel fabricator friend who is into Japanese 1980’s bikes. He says they often have fueling troubles because the carbs are gummed up. So will let him use it and when I need a bit of welding, know he will willingly do it.

There was a big bulge in one of the new tyres where it had sat for donkeys years. When inflating, it went pop, so got a new inner tube. To my delight, there was no bulge, it was the inner tube that was creating it and something I had not figured out. So if you get a machine with flat bulging tyres, would recommend just replacing the cheaper inner tubes first.

Then split the engine from the rest of the machine and took the clutch off. This went very easy. The photo is of the friction plate. Saw the springs were compressed at one end, noted that I have to replace them the same way round. Got a new clutch plate from Howard Spares, but it did not fit over the pins. Asked Howard Spares what to do and was advised to tap the pins to fit. Decided to do some measuring first, the pins were fine, it was the clutch plate holes that were not correct. They had variations. So had to file them to fit the drive plate pins, ensuring they had the same contact area both ways. The old friction plate had cracked and did not want to risk overloading a couple of holes. Wanted the load to spread evenly both ways. Because it would have load two ways when using the reverse gear. It was a bit of a pain to do, especially after forking out £50 for the plate.

Put it all back together, fitted the engine, did a few small other tasks and fired it up easy. Ran well too. So took it to the ground to do some work. The clutch only operated with a small amount of travel, but did work OK. But got it stuck straightaway in a furrow, the wheels stopped driving. It was hard work pulling it out. The rotovating when very well, but kept loosing drive. When I went deeper, the machine shot forward. Finished the work and took it back. Read the manual and noted the springs in the wheel hubs should be done up tight, then slacked back half a turn. Its a safety feature, if you hit an immovable object, the wheel friction disks will stop the drive. Whoever fitted the new tyres originally did not do this and I just thought it must be correct. Looked at the manual pictures of the clutch springs, the coils had a consistent spacing. So think over 50 years the springs have lost some compression length, which explained the fully feel on the clutch lever. Contacted Springmasters at Redditch and they can help me out. In the winter will whip the engine off and send the springs to them.

Overall extremely pleased with how its all gone. The throttle linkage is very loose, resulting in poor throttle control that is very apparent when moving the machine around. But am going to fix that with some M5 ball joints and threaded bar. Will bolt the spring below to the operating arm too, the hole is enlarged where the spring loop goes through. Going to use it at the weekend to chop some weeds up in the ‘clean’ bit if the young orchard. My Trusty’s wheel gearbox finally gave up the ghost. But have a plan for that, more anon.

[sidevalve5]

Thanks Andy,

Did not know what to expect when I arrived at the hospital as had no contact with the consultant since the day of diagnosis 14 months ago. They have developed less invasive techniques, so a wire with an ultrasonic probe burnt the inside walls of the deep vein. A chemical foam was injected into the shallow vein. All went well and will hopefully continue on the road of a rapid recovery. Was previously painful to walk after 20 minutes or so, more difficult too over rough ground. Could only use the Trusty in short bursts.

Was offered a cheap Clifford MkIV after a chap made a bonfire too close to it. He lit it and left it to burn. The next day he found that the bonfire must have flared up overnight, the Clifford’s tyres caught, the machine was wrecked. My Clifford is in good condition, but has no compression and the exhaust has broken off. This exhaust formed part of the barrel on the Jap 6. So thought the burnt Clifford would be good for spares, it has an intact exhaust and compression. Think the Lucas SR4 mag is OK, but the HT pickup is burnt, so have not tested it yet. The Zenith 24T2 carb body is black, but seems OK otherwise too. Have found a chap with an ultrasonic cleaner. His main business is automotive lighting, but he also restores British bikes. We had a good chat on the phone, he knew all about gummed up carbs. He also plays guitar and says broken strings make excellent jet cleaners, another tip was to put WD40 through an orifice and check the pattern of what come out the other end. Am going to take the Gem carb, the Trusty and black Clifford Zenith’s. Whilst I cannot use the Trusty until fit enough, be good to get the carb cleaned in the meantime. The butterfly valve is a poor fit in the ventri, so do get air bypassing it, the tickover is a bit too quick. Will have a look at what I can do about that too.

Grahame

[sidevalve5]

Hi all,

Work on the Gem will be curtailed for a while. Was on an 18 month NHS waiting list for an op for a blocked vein on my leg. With 4 months to go had a call to say there was a slot available yesterday from a cancellation. Took it and am now laid up for a while. When I get active again will be flat out on my veg plot, soft fruit and orchard in my spare time, am still working. So no time to play with machines, unless urgent repairs. One of the problems with using such old kit is the constant maintenance to keep it going. But that is part of the fun, get great satisfaction from getting them to operate at an optimum level and then working with them.

Have never used a large walk behind rotovator with rubber tyres, so do not know if the direction of the cleats on the tyres makes much difference. Someone told me that they should be opposite to a tractor years ago, so that is what I understood. Have a Clifford Mk1that came with the tyre cleats pointing backwards. It was owned by an old boy who became so infirm he gave up his veg growing and swapped it for a load of logs. This new owner used it for years until it stopped working with no spark. Muggins bought it for £40, the vendor was very honest and said the coil had packed up. He thought it could be repaired with an external Honda 90 coil. So had a go, stripped the secondary windings from the original coil and hooked up the primary windings (which I understand rarely fail due to their thickness) to the external coil. But it did not work. Put in a Villiersparts coil and then had a good spark. Not the cheapest repair, but do use the roteo (Evesham slang for rotovator), it does a good job for its size and sounds a lot different 4 stoke singles. It will not chop in tall plants and is unstable over rough ground due to the wheels being so close together. If it hits a big stone, the flywheel will turn on the crankshalf, it then has to be re-timed. But its a gas to use.

My other roteo is an early Clifford Model A with steel wheels. Bought it in the early 1980’s from a chap who was packing up his part-time market garden. He wanted £70 for it and had a Trusty for sale too. Did not really want the Trusty, but it had a rebuilt engine, plough and cultivator frame, so agreed to take it off his hands for £25. Have used that same Trusty for 40 years. Its well and truly knackered now, apart from the engine and clutch. Have another two Trusty’s I bought in bits, both with Douglas engines, one with a reserving gearbox and transmission brake. The plan is to get one going in tip top working condition and put the Jap 5 engine from the retired Trusty on the Clifford. That has hooked tines on the rotor and I think does a better job than the L blades. Got some new tines years ago from Chester Hudson, he seemed to have massive stocks of all sorts of parts. I wonder what ever happened it all, does anyone know? The Clifford used to loose its gearbox oil from leaking seals where the rotor shaft came out of the central casing. Understand the original seals were leather, would like to replace them. Does anyone have any ideas about that too?

Will post an update about the Gem when its either working, or if there is a serious problem.

Grahame

[sidevalve5]

Dear Andy,

If the pump is causing the problem will get a new pattern diapham from China a £5.80p. Always fit a fuel filter to my working machines as a small bit of rust can come off the inside of the tank, rubber particles from pipes, even with E5 petrol and dirt from the petrol can when filling up. A local hire company always fit a fuel filter to their new plant.

Looked at an Irish lad on YouTube undo the bell housing. Jack on the rear, a trolly jack under the engine, disconnect the fuel pipe, throttle cable, kill switch wire, undo ten bolts and it easily pulls apart. As you say, a piece of cake. But he found the adaptor plate bearing had broken up, it rattled around and damaged the six pins. Have heard all sorts of tales of broken shafts, gearboxes and bearings on Gems.

Have limited use for the rotovator and indeed have a low opinion of them. They are good for chopping in the crop ready for ploughing, or preparing a seedbed when the soil conditions are just right. If used when its wet, they compress the soil structure, especially in our Evesham clay and any clods produced dry out to big hard lumps that you cannot get down. But the Gem looks like a good machine and with little work, can find a use for it. Got a Clifford Mk IV I want to restore if only because I like the colour and shape of the bonnet.

Grahame

[sidevalve5]

Hi John,

The tread direction was what was on the machine when I collect it. The tyres have been fitted, but have never touched soil. They were deflated and the righthand one ‘set’ over towards the gearbox. When pumped up there was a bump on the inner wall, so it rubbed against the gearbox. It was a devil to move the machine. When I got it back I deflated the tyre, pulled the area of the distortion back, held it there and put some wind in. It wetn pop, so I need a new inner tube.

Have always understood that rotovator tyre tread direction is reversed to that of a tractor to prevent the machine being pushed forwards quicker than it should be by the action of the rotors. Be interested to hear what the general opinion is.

Grahame

[sidevalve5]

Dear Andy,

A big thank you again for your sound advice.

Am 95% certain the rotovator was a good machine before it was put away 25+ years ago. The only nagging doubt I have is over the clutch, why is there some ‘feel’ on the handlebar lever only when both adjuster are tightened to their full extent. Do not want to spent time and money on it, only to find there is something broken that cannot be fixed with the clutch. If it is just worn friction plates, or the bearing knackered on the engine adaptor plate, then obviously can do those. But as you say, can only assess this once I have split the machine. Was really after advice from someone who had a lot of knowledge of Howard Gem clutches and what to look out for before I undo the bellhousing. Decided the re-commissioning process was to get the engine running first and if that was good, move onto the clutch. Like to do some research before I tackle a job I am unsure of. Find that the experience of others is invaluable in that respect. It can save time and possible damage if you try to disassemble a part that has a retainer you are not aware of.

Have always used petrol and an airline for small parts cleaning. Found Gunk and a pressure washer great for removing thick oily sludge on engines. Mostly petrol and a good brushing has removed gum on carburettor’s, except the really hard to shift historic coatings. Have googled ultrasonic cleaners for carbs and some say they are brilliant, others say so-so because the small passages are not fully cleaned. But am going to take your advice and see if I can find someone with one and chuck the carb in.

Have got a Zenith 24T2 carb with an adjustable jet on the Jap 5 on my Trusty. Replaced the original Jap carb with the Zenith and it was that that I made up the new linkage for. The Zenith was removed from a Trusty that was left outside for decades. Put a service kit on it from Villiersparts, that included a new throttle spindle. The old one had a big flat on the linkage side, so air could be sucked into the carb. The new spindle then made a huge difference at tickover and throttle pickup, which is so important on a Trusty. But sometimes it will start by the third swing of the starting handle, others not even after twenty on full choke. It appears it is not getting enough fuel to start it from the main jet to the orifice in the ventri, with the chamber not being clean and smooth, preventing the petrol from being sucked through it with a single swing of the handle. Luckily a Trusty can be started with a strap, so I can get it to go. But re-built it last year, so it has full compression, getting a bit long in the tooth to keep having to turn in over with the strap. When I find someone with an ultrasonic cleaner, will take both the Walbro and Zenith carbs for a clean.

Have attached the pictures. One way or another I know I can get the fuel system sorted out quite easily. Have a feeling it may be the petrol tap only delivering a fast drip, in turn making the original diaphragm on the fuel pump let air bypass it, delivering frothy petrol to the carb. That could be the real cause of the problem. But having the carb ultrasonicaly cleaned will not hurt either. Will be very interested to see the results to both carbs. Have you ever taken a clutch apart and if so, what did you find.

Grahame

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[sidevalve5]

Many thanks Andy for replying to the post.

Will work my way through the fuel system until I find what is the matter. Got to get the petrol tap flowing freely first. Also will soak the carb in cellulose thinners, acetone or white vinegar. Think I will experiment with all three on different parts to see which one performs the best. If there are still bubbles in the fuel from the pump, will have a look at that too. The chap who left me the machine had an ultrasonic cleaner, but I think it was sold along with his vast array of plant and machinery.

Agree about the throttle linkage, will make my own. Can get a pair of M5 ball joints for £5.20p off ebay which will give a stable mechanism. Have found original linkage rods going through holes that can enlarge over time. With a big single at tickover it can cause the throttle butterfly valve to flutter, so the revs are not as steady as they could be.

Agree again the most likely cause of the lack of clutch operation is sticking plates. My only doubt about this is when I picked the machine up there was zero resistance on the clutch lever on the handlebars. It was only by tightening both adjusters to their maximum, could I feel something was moving. Managed to download the service manual and it does go through the clutch itself, but limited info about the mechanism that operates it. The photos are not very clear. It looks to me the clutch lever at the gearbox end has a pawl on it that engages with the clutch trust sleeve that in turn presses against the clutch trust plate on the clutch unit. It is this area that I have concerns about as if something is broken there, it could be terminal for the machine. The other thought I had was the rotovator was used with the adjusters up too tight, inducing clutch slip, eventually completely wearing out the friction plates. Which may account for all of the adjustment used up on both ends of the operating rod before any ‘feel’ is felt by the clutch lever. Or the nut that secures the clutch unit onto the clutch shaft may have worked loose, so the whole assembly is pushed towards the engine. As previously, any advice is most welcome before I split the machine.

Grahame

[sidevalve5]

Hi all,

An update on the Trusty. Struggled to get the clip off and did not want to grind it out unless absolutely necessary. So decided to firstly try to do a (agricultural) repair in-situ. The shaft was twisted, so jacked up one wheel, put another jack under a spade lug and another jack on the other wheel’s spade lug, which would turn the wheel in the opposite direction. Put some firebricks around the shaft and heated it until it was a dull red. Then raised the jack on the raised wheel. Tried to ‘bone’ the twist on the gearbox top. Let it cool and it was a lot better. The steering dogs do still get stuck if you move them too far along the shaft, but had already put a bar with hooks between the original steering lever hooks so I did not have to move the levers out to the maximum.

It was worked well whilst scuffling and then threw a chain again when starting off on the left hand steering lever first. The cause of all the trouble is the wheel and pinion shafts on the left hand gearbox having bearings that are both shot. Everything wobbles around, including the chain plate wheel. So took out the steering lever stop bolt, fitted 3off 3/8” thick, 3” diameter nylon discs to it to keep the plate wheel straight. Now have got the machine working again. Realize it is only a temporary fix, but am hoping it will do for this season. Have a couple of later Douglas engine sliding axle types that I intend to use in the future after rebuilding the clutches and engines. Will retire this 1945 JAP engine 4 stud wheel one, although have rebuilt the engine last year, so am going to put it onto a Clifford Model A Mk1 rotovator.

The above entailed ‘a whole lotta bodging’ and would not recommend it unless you are like me completely stuck with no spares. It took an age working in the field and is still only a ‘get you going repair’.

[sidevalve5]

Dear Geoff,

Many thanks for your invaluable advice. Found that my machine did not have a screw with locking wire over the slot. But a spring clip with a pin that would locate the sprocket bush. The flat spring clip goes about two thirds around the sprocket hub. Still have a problem though because the clip appears twisted and no matter what I did I could not get it to clear the bearing housing. Have made a special tool, a piece of steel with a slot in it the same size as the hub to slide in between the bearing housing and the clip. So the clip should straighten enough so I can push it off the hub. There is very little clearance between the housing face and the clip, so made the tool out of the thinnest steel plate I could find. A paint tin lid. But think it will not be strong enough, but have not tried it yet. Will give an update as to how I get on.

The continuous rain has put back any chance of ploughing though. Am like a lot around here with ground that needs working, but its too wet. Am concerned the shaft is twisted and if so, am not sure I can straighten it.

Best wishes,

Grahame

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