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Collection, Preservation and Display of Old Lawn Mowers

SUFFOLK SUPER PUNCH POINTS ISSUE

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I have no spark at all after renovating my 1966 Suffolk Super Punch 14" and I may need to remove the Flywheel ,as with the points fully open, I am only reading 1.1 Ohms across the points ,so maybe why I have no spark at the plug. I suspect the Condenser could be nearly dead short or something else is shorting across the points, they are clean and 20 thou gapped and I have tested the Magneto Coil Secondary 3.5 K Ohms which is normal and also fitted a new Spark Plug HT Cap as the original had a break between the Carbon slider and the spring so I was reading Infinity Ohms from the Screw in end thread to the spark plug toucher. What is the usual expected value of the Primary Coil on the Magneto please, as the 0.8 Ohms extra above my test lead resistance of 0.3 Ohms giving my 1.1 Ohms Reading could be the Primary, though I expected 10 to 20 Ohms Primary Coil resistance. My Test Meter is a very accurate calibrated Fluke Model 29, so the readings I have quoted will be pretty exact.

I have now proved the problem is the points, when they close they are not shorting the Primary winding of the Magneto to Ground to allow Swell and Collapse of the Primary Voltage, thus no HT from the Secondary side. I have cleaned the points a few times this evening and I had a good strong spark for about 5 spins of the flywheel, then nothing again. When I checked the same situation exists as at the start, not shorting across the points to ground the Primary Magneto Winding. It appears about 1 ohm is the normal Magneto Primary Coil Resistance.

Could this be an issue with the pressure being applied at the points contact surfaces when they are closed being insufficient to reliably short down the Magneto Primary ??  Can the points be carefully removed thro the Aperture in the Flywheel to closely inspect them or is it Flywheel Off please.

Forums

Ransomes-Suffolk Sun, 14/06/2020

I would take the flywheel off to enable you to get good access to everything for troubleshooting. Other than cleaning the points, there is very little that one can do easily through the aperture. The attached image shows a simple tool which I made for flywheel removal (just a piece of 10mm thick bar with holes drilled to suit flywheel and three bolts). If you can make something similar then removal of the flywheel is a quick and easy task.

RIPMAXRAPIER Sun, 14/06/2020

Ransomes Suffolk, many thanks for your reply, I wish I had done that as I read in one of the contributions from somebody else just to back the flywheel nut off till it was well clear of the end of the crankshaft and strike firmly with a hammer and the flywheel would release, this I did and the flywheel never budged and now I have damaged the nut and need to find a replacement nut. The Crankshaft threads are fine, no damage (thanks goodness) This afternoon I actually got the flywheel off intact by gently tapping the rear with a light hammer as I turned the flywheel, removed the whole Wipac Magneto Assembly and took the points off to check them and as I started to lift the points away from the backing plate, the Primary wire just fell off, so it obviously had not been well soldered. I have everything now fixed good as new, points are very good and good pressure to close them, I am reading 0.9 Ohms across the Primary of the Magneto, I sort of expected 10 Ohms or so can you tell me if 0.9 Ohms is normal for the ,Magneto Primary, or is the embedded condenser shorty. Earlier today when I built the Magneto back in and set up the 20 thou points gap I turned the flywheel by hand and got about 5 good strong sparks, then it stopped sparking again, if you can please let me know the Primary Resistance value it would confirm if I actually need a replacement Magneto (because of the shorty Embedded Condenser. Help much appreciated Paul

wristpin Sun, 14/06/2020

Not that it’s likely to have much effect but the points should be 18 thou for that mag. That figure is usually cast into the flywheel.

RIPMAXRAPIER Mon, 15/06/2020

Angus,

 

As an experiment earlier I actually tried different gaps 15 thou, 20 thou and 25 thou in case the difference was very critical, but no different still no spark, I need to find out the spec Primary Magneto Coil Resistance to determine if my Magneto is actually the source of the problem. After having removed the Flywheel, the complete Magneto and the Points and carefully and meticulously cleaned everything and repaired a broken Magneto Primary connection to the Points, I thought maybe the connection had been the main issue, but after refitting and testing, still no spark. I did the Fluke Resistance meter test again and back to square one Points not shorting Primary winding to Chassis, so I have just removed the Magneto to the Kitchen bench where I have really good level of lighting and I found that if I opened and closed the points quickly I was getting a few Ohms, not 0 Ohms as I expected, but if I operated the points in a fashion like the eccentric cam would, I was actually reading very high ohms directly across the points with the Mag Primary wire disconnected, so under good lighting I got the magnifying glass out to look at the points contact faces closely, and on the fixed face I was shocked after all the cleaning I had done to find a deep narrow black pit. Emery paper was having no effect so I had to get a flat miniature file out of my set and file for a considerable period of time to get the contact flat and clean, now regardless of what way you close the points quickly or more slowly like the cam, I have a dead short, so what has been happening was every time I put the points back and they operated for real from the cam, they have never actually been shorting the Primary to chassis, so no collapse of the magnetic field energising voltage.The points were clearly well closed and looked as if everything was good, but it was not good in real time operation on the Cam. I have just refitted everything and set my 18 thou points gap and WE HAVE SPARK good and strong. This has been the hard to start problem with this mower for 2 years and it is great to finally get to the bottom of it, all I need now is a new Crankshaft Flywheel nut and we are all systems go. Many thanks to all who contributed to help with this. I still would like a new set of points but I think chance would be a fine thing. The Points contact faces are slightly offset but I don't see how you could bend them without endangering damaging the points.

wristpin Tue, 16/06/2020

All good then! I use a small carborundum slip stone for bad points but that does mean dismantling them . Its possible that some of your dodgy meter readings could be down to the the moving point being a bit sticky on its pivot. A bit of offset doesn't matter, its the faces coming together with no daylight showing on one side that is important for reliable operation. 

Have you tried Jon Cruse for a new lht nut ? (Hailsham Mower Centre)  Alternatively Tracy Tools will sell you an LHT tap to clean up your nut .

RIPMAXRAPIER Tue, 16/06/2020

Angus,Thanks again for your invaluable experience and help, I have a new nut coming from a guy on E Bay who was selling a Flywheel and Nut but he is happy to sell me the nut alone. Is the nut 3/8 UNF  24 threads per inch as there is also a company who sells lots of UNF and UNC Locknuts, I think this looks like 24 tpi 3/8 .

The points really surprised me, as I had cleaned them while I had the mower stripped down,  and I used fine Carborundum Paper and to the naked eye, they looked very clean, so I was always ruling points low down the causal chain. Yesterday when I removed the whole Magneto the points to the bare eye looked clean, but under good lighting and a strong magnifying glass one face was immaculate and the other had a very fine T Shaped deep pit in it, so I got out a miniature Flat File and filed for some time to get the face flat and clean, then finished off with Carborundum Paper and when I did the points test simulating a slow closure like the Cam would give, now I had 0 Ohms every time and actually it didn't matter any more whether you opened the points slowly or quickly. I reinstalled everything and set 18 thou and working great, I know the mower will start now and I am confident that this was the Root Cause of my 2 year Hard to Start issue, which I had proved no spark several times, but I had nowhere to work at the mower. Now the neighbours will be glad to not have to watch me pulling the start cord to the point of exhaustion every time I go out to mow the grass. I even had one who took pity on me and offered me the loan of his Bosch Rotary Electric at one stage. By the way my original fuel tank is repaired and fitted, did you get the photos I sent of the before and after ? Its been a labour of love, but I love to see old equipment preserved for the young people of today to see how good our  British made Grass cutting equipment was all those years back

Many thanks Angus

wristpin Tue, 16/06/2020

there is also a company who sells lots of UNF and UNC Locknuts, I think this looks like 24 tpi 3/8 .

You don’t mention the magic words “left hand thread”  - are we to take that as read ?

or..........!!

RIPMAXRAPIER Tue, 16/06/2020

Yes I meant Left Hand Thread Angus, just want to confirm the size and type in case the one from E Bay is damaged. It measures like 3/8 24 tpi LH UNF Thread, does that sound correct to you ?

Also have found many companies supplying 3/8 Left Hand UNF 24 TPI Dies and Taps for about £8. I just hope the one from E Bay is OK, if so I am in business. The mower looks so fresh and nice that I am going to clean it well every time I use it and most importantly keep up a regular Lubrication Schedule and Oil and Air Filter changing.

My Grass Box is a Plastic one, but I thought when I was about 10 years old I remember the Grass Box was metal, but not to worry it collects the cuttings and last time I used the mower last year it was cutting very nicely, nice fine clippings.

I might actually consider painting the Grass Box with a nice Acrylic Green as I have a new Decal for it. Its just a bit grubby looking.

UPDATE

Found an Old Lawnmower Shop called Maine Mowers in a place called Cullybackey, had the LH Thread Nut with me showed it to the guy and he went straight to an old style Wooden Drawers unit ( Like the Two Ronnies Four Candles sketch) and when he opened the drawer, he had several brand new ones that have obviously been there for years, sold me one for £0.50.

Came home and put everything back together ,primed the carburettor with the tickler, and BINGO mower started and running quite well even before setting up the Fast and slow running jets. Can't describe the Feel Good Factor and pure satisfaction of getting this all done. All I need to do now is fine set the Carburettor needles and adjust the clutch, as when it started ,it tried to exit my garage with the roller door closed, a bit scary but I got it stopped. That lawnmower shop was only 4 miles from me and I didn't know it existed, a local guy looked at the nut and just immediately said go to Maine Mowers, its a real Aladdin's Cave, dare say if I need a set of points at some stage, they might just have them. The new height adjusting knob for my Qualcast also arrived this morning so I got it fixed too. I was mowing the grass on Monday and as I was rolling along the height suddenly dropped, the shaft of the height adjuster plastic knob had sheared. So that's 2 mowers fixed in an hour, I feel really good now.

All the best Paul

wristpin Thu, 18/06/2020

Found an Old Lawnmower Shop called Maine Mowers in a place called Cullybackey, had the LH Thread Nut with me showed it to the guy and he went straight to an old style Wooden Drawers unit ( Like the Two Ronnies Four Candles sketch) and when he opened the drawer, he had several brand new ones that have obviously been there for years, sold me one for £0.50.

Wonderful!!

RIPMAXRAPIER Fri, 19/06/2020

Angus,

John Cruse says he can sort me out with points if it comes to that. Good job I managed to get the 3/8" UNF LH Nut locally yesterday. The one from E Bay arrived this morning and it is LH Thread but 1/2" UNC and about twice the weight of mine, but it was always going to be a risk, and I might actually buy a spare one to keep from Maine Mowers.

Good to know about John Cruse too.

wristpin Fri, 19/06/2020

Points. Have you asked at Maine Mowers?

I believe that you said the eBay seller was selling a flywheel as well as the nut. Wonder what that fitted? 

RIPMAXRAPIER Tue, 23/06/2020

I actually asked the old man working at the mowers who got me the nut if they had new points but he said he would look as he was sure  there were no NEW points but there may be a set somewhere 2nd hand that might do, so next time I am out there I will see if he found any. Its a real Lawnmower Cemetary, out the back with lots of different makes, I might actually have a browse and see if there is a Mountfield Emperor Resting In Peace, and if there is, and the price is right, I might just buy it and try to do a Lazarus miracle on it (Jesus raised him from dead) I actually had a Mountfield Emperor for many years and it was brilliant until the Clutch on the roller drive eventually gave up, and I could not get a clutch anywhere, although after I had stopped using it Mountfield sent a letter to say they had sourced a Clutch and Spring for me in New Zealand, they said it was the last one in the World, so I bought both, then my first marriage ended after 26 years and she took the mower ???  and my 10" Celestron Equatorial Mount Telescope.

I had a very uphill lawn and had a lot of hard pushing when cutting the lawn especially as the grassbox filled and got heavier., before failure the mower became a sort of Sometimes Self Propelled (With some pushing) then it became a push mower. It was a 17" Cut.