I've been collecting side pull mowers for years as I wanted to convert all my older mowers to pointless ignition Norm but possibly reversing a points coil may work with a Powertorque module ,when a tried a Powertorque module on a standard points coil I had to spin the motor a lot quicker to get a spark.
From what I've read Vm on the Stens Module ,the coil will only work one way but not the other ,so if you don't have a spark with negative earth you change to positive earth on the module to get a spark.
I was thinking the Stens module would work with a negative earth with this coil setup ,must be the same way the Victa modules work .
The Victa module just has one wire connection so I have installed it as standard with negative earth.
The coil can't be turned on it's side as the coil hole is rectangular and not square ,what is difficult to see in my previous images is a side keeper that locks the coil tight on the core ,one image below shows the tab of the keeper at the back of the coil and as it goes side ways I didn't want the tab on the flywheel side.
I didn't take a lot of notice when flipping the coil over on the core but the brass keeper worked with the plug wire up or down.
Thanks Max, That explains it well. Looks like your Victa has the orientation horizontal on the core compared to mine which is vertical. Also, in my case, the arm on the core is forming an almost perfect square in the centre of the coil, not rectangular. That is what was throwing me off.
Incidentally, I've just been told that BSA Bantam coils will work on early Victa and are interchangeable as both used Wipac ignition systems, but I guess the only way to prove this would be to test one. They are Made in India and very expensive imports from UK and US, but I might be able to obtain one for a reasonable price direct from India.
I was thinking the Tecumseh pointless coil may work on the Victa laminated steel core ,the only problem is the steel core would have to be filed down slightly to fit the Tecumseh coil.
With the Tecumseh coil it would not need to be installed backwards.
Hi Max, How thick is that coil it looks fairly wide and not having a curved face makes it stick out further. I have a few Tecumesh motors here so I could pull the coil off one and give it a try
Hi Norm/Max, I was wondering about Tecumseh coils too.
Max, this is probably the dumb question of the day, but instead of reversing the coil, why not simply reverse the wiring? So use the earth wire for the positive and the positive wire for the earth? The reason I ask is that if I test an external Victa flywheel coil with the multimeter, I get the same reading in KOhms through the earth wire as the positive wire. Wouldn't reversing the wiring be the same as reversing the coil and using the same wiring?
I think the Tecumseh coil will not work on the Victa Norm and Vm as looking at the width it's 32 mm so is too long for the Victa core centre.
The thing is the Tecumseh coil should fit a Villiers torque major or Kirby but will not be a simple swap. It looks like the Tecumseh coil is molded onto the core or molded onto two metal tabs that are spot welded to the core.
Might have to see if this Tecumseh coil will work on the Villiers motor , don't throw out the coils Norm if you throw out the Tecumseh motors as they might be usable on a few motors.
Originally Posted by vint_mow
Max, this is probably the dumb question of the day, but instead of reversing the coil, why not simply reverse the wiring? So use the earth wire for the positive and the positive wire for the earth? The reason I ask is that if I test an external Victa flywheel coil with the multimeter, I get the same reading in KOhms through the earth wire as the positive wire. Wouldn't reversing the wiring be the same as reversing the coil and using the same wiring?
Yes I was thinking about that Vm, but don't think the coil would work properly, coils are made to work one way.
Generally I would say no you can't reverse the primary windings polarity ,I have seen car coils wired backwards on oscilloscopes and the spark is completely wrong even though the engine will run.
Does it matter which way an ignition coil is wired? The coil will work efficiently and put out the same voltage either way it is hooked up, but the spark plugs are more sensitive when it comes to polarity, hence our second and more important definition. Coil polarity should be such so as to provide negative polarity to the spark plugs center electrode.
With a car coil , Coil Polarity (In relation to spark plugs) Coil polarity should be such so as to provide negative polarity to the spark plugs center electrode.
It has been found that it takes approximately 15% less voltage to form an arc at the plugs, if the hotter center electrode is negative, and the cooler (by comparison) ground electrode is positive. The center electrode is hotter since heat transfer from the tip must make its way through the porcelain insulator past the sealing gaskets to the shell block and then to the water jackets.
If your center electrode is positive, your car will probably still run fine until, with its 15% handicap, it exceeds the coil output. If you live where temperatures dip down to 0° you may not get your car started. Driving with a full load and accelerating hard up a hill may cause an ignition miss. If your ignition system is well-worn to where you have various voltage losses, you could get a miss.
I know you can test the polarity on a car coil and I guess the same test should work on a mower coil but you will need an old needle volt meter.
Hooking up a mower to an oscilloscope would show straight away the effect of reversing the primary windings polarity, but I think the volt meter test would be a quicker test.
First Video is how the coil works and the other two show what the spark should look like on an oscilloscope.
After checking spark plug terminal current with a 10 volt analog meter ,the Victa internal coil (inside flywheel) and Villiers torque major were both positive to the spark plug center electrode.
The Powertorque and side pull full crank and the mower I converted were all negative to the spark plug center electrode.
To check the voltage you have to spin the motor over as if you were starting the motor, a very slow spinning motor gives a false reading.
The mower I converted starts first time every time except if I don't prime the carby when it's been sitting for a day. Also takes very little effort on the starter to start.
Just shows you that the points coil even with a module to convert the ignition to pointless is never going to be as good as the Victa pointless coils.
The coil design will control if the plug is negative or positive.The direction in which the wire is wound around the coil. The North-South polarity of the magnet(s)
For plugs in a positive polarity position, more electrode wear will occur at the ground electrode. Plugs in a negative polarity position will experience more wear at the center electrode.
If the direction of current in the first pulse is such that the spark plug tip is negative that is better because the tip gets hot and some thermionic emission takes place assisting spark formation .The term used for this by old school Auto sparkies was "Coil Polarity "
Image below shows magneto with positive to the plugs electrode then negative to the plugs electrode .
Hi Max, So I guess this can only mean that the early Victas with coil inside flywheel were negative earth, but the later ones with coil on outside of flywheel are in fact positive earth?
Yes that's the way I see it , looking at the primary winding in the coil the start of the primary winding that is closest to the core is the negative and the other end of the primary winding furthest from the iron core is the positive side of the primary windings.
The primary windings in a mower coil seem to work the opposite way to a car coil probably because the mower coil uses a magnetic field for current flow in the primary windings and a car has a battery for current flow.
