Reply To: Magneto Testing

[sidevalve5]

Dear Andy,

I do agree with you that there is a lot of rubbish on the internet. But the primary sources of my information was obtained from the repairer’s The Magneto Guys and the supplier of the capacitor, Brightsparks. Please view their websites to see what they do and advise. I would NEVER post something on the forum that I would think is dodgy information.

FYI, I am actually a bit more experienced and knowledgeable about magneto’s that I have indicated so far. Have worked on them in one form or another most of my life, but only in the last 15 years have I actively restored them back into use. All have been on old horticultural tractors and machinery that have lain around unused for many years. Some have even been left outside for decades and were in very poor condition. I have got every each one to work that include: Villiers, Bosch, Wipac, Wico, Kolher, Honda and Briggs & Stratton. The last two included transistorized modules. In nearly every case I have successfully stripped them down, tested the HT coil’s resistance with a multimeter, thoroughly cleaned them, carefully reassembled then, using new parts as required, tested the LT resistance, then spark tested them. I have got ALL to work, except two that failed the HT resistance test. A new coil fixed the problem.

The whole point of my original post was to tell others of my experience and spread some of the knowledge that I have gained from REPUTABLE magneto specialists. It was to help others who maybe did not want to pay for the fair, but expensive magneto specialists to look at it in the first instance. But to have a go themselves if they felt confident enough. I personally get huge satisfaction from getting a machine that most would view as scrap and after spending my own time working on the mechanical parts, bring it back into full operational condition again. That includes the ignition system.

The point about replacing the condenser with a capacitor I wish to mention yet again. It improved hand starting and tickover on many of the engines I worked on. Please read Brightsparks advice about the matter and indeed have fitted one of their capacitors myself. For those who may want to just have a single mag to improve, would suggest you have a look at their products.

Lastly on the thorny and unfortunately contentious matter of multimeters. I would readily agree that specialist magneto repairers have an extensive range of dedicated test equipment that is vastly superior to a multimeter. However if you look some of the photos on The Magneto Guys and Brightsparks websites, you will see plenty of evidence of them being used. But this subject was not about that, but how a chap with some mechanical knowledge could test a dead or poorly performing magneto in his own workshop without spending a great deal of money. A spark tester and multimeter will cost less than £12, a magneto specialist charges £75 to do a test. Add p&p, a set of points and a condenser, which I have no doubt they will advise, then price starts to be nearer £150. Believe George is a bit cheaper than that. It is not just getting a multimeter, clicking it onto Ohms section and checking if a circuit is open or closed that I am suggested anyone does. As it happened I only recently purchased a new one. The old one’s probe leads had broken and then gave an intermittent signal (dodgy for resistance testing). Have dug out the instructions. To test the LT circuit, turn the knob to 200 ohm and the resolution will be 100m ohm (100th of an ohm). To test the HT circuit, turn the knob to 2000k ohm and the resolution will be 1k ohm (1000 ohms). The published instructions state the accuracy of the reading will be + or – 1.2%. Kohler, Honda and Briggs & Stratton publish the resistance figures of their coils for service engineers to refer to. Why on earth would they do that if they thought a multimeter was not a correct test instrument for the task. As stated previously, I do have a lot of time for George, without some of his parts, I do not know if I could have kept some of my machines running. But one thing he is definitely not is the guru of all things in the magneto world. If you and him do not trust a multimeter, am afraid you are in a very small majority indeed. I do respect your alternative viewpoint, just that I do not agree with it. I have no idea about your box of old coils, or how they were tested. All I can say is about my own experience, of the multitude of coils that passed the CORRECT resistance test, they ALL worked fine. The two that did not were replaced and the ignition problem was then fixed.

Best wishes,

Grahame