And now to a spark problem on my MH 20 coil ignition tractor.  Every year when I go to start it up after the winter layoff it will never start on a 6V battery - even a new one - yet the spark always looks good on the points. 

I put a 12V on it there is an immediate start up.  What is this?  Is it faster cranking or a better spark?

Answers invited  ????!!!

John

John:

I am guessing bad wiring or bad connections under the dash like just off the amp meter or on the switch.

If you have a digital volt meter you should hook it up to the power lead on the coil  it should read 6 or more volts with just the key on, once you push the starter button I am guessing your voltage drops to 3-4 volts that is why your tractor won't start.

When you hook the 12 volt battery up to your tractor it is much more forgiving as now there is twice the voltage. If you check the volt meter now with the 12 volt battery wile cranking I bet it is well over 8-10 volts at the coil power lead so you will get a great spark and the tractor fires right up.

Also you might want to check if the coil is hooked up backwards I was told by Dick Le Fever if it is hooked up backwards it will still work but it will take more power to run it and put out a weeker spark.

Dick had a display set up at one of the Pensylvania shows demonstrating what hapens if the coil is hooked up backwards it was very interesting.

Also you may want to try a different coil the one you have may be bad, sometimes they start to break down inside and take more power to fire.

Just a couple thoughts,
Joe

Joe,

I'll check on whether the coil is the right way round or not, but what is strange is that after that first start of the season and , say, a five minute run, it will start all through the summer on the 6V battery.  Also I would say that I have checked the spark whilst on that first cranking with a 6V and it always appears strong.  But I am only too aware that there are sparks and good sparks!!!

I was talking with Lyn Jones (who you have met) recently.  He says that when he has a magneto that has "gone off" he takes the points out and rubs them up on what we call a whetstone ( a flat very fine carborundum block which we commonly use for sharpening wood chisels) and he says that usually does the trick.

I wonder have you ever come across the gadget that was used in old magneto repair shops for testing the strength of sparks.  Apparently they were something like a glass globe with a spark plug and a connection where you could increase the pressure in the globe to simulate "under compression" conditions in the cylinder.  A spark that will fire in the open will not necessarily fire under compression.  I've searched for one of these gadgets at auctions but never come across one.  They must be good - taking the guesswork out of assessing spark quality,                                      

John

John:

I have one of them machines similar to what you are talking about but it is for testing the spark plugs only and cleaning them, it was from an old chevrolet dealer years ago. I haven't used it for quite some time now but it should still work but this has it's own spark maker so it won't test the spark comming out ot the magneto. I wold imagine if a guy took a long spark plug wire and just used the machine for putting the pressure on the plug it would do the test you are talking about.

What you are looking for is something that tests the spark comming out of the coil to see if it is strong enough, there is a really reasonably priced gadget like this on ebay in England Item Item number: 160673739092 also there are many others like it that may be cheaper.

This gadget is designed to test the spark on GM HEI ignition systems wich usually put out about 80,000 volts that should be very similar to what a good magneto should put out maybe you want to give one of these a try.

Just a thought,
Joe

Joe,

I will check that item out on e bay.

another thought about magnetos came to me last night.  When I need a magneto compeletely reconditioning I send it to an "old timer" who actually used to work for the UK's largest magneto builders.  I also used to send him the occasional "gone off" magneto that we have been discussing.  More than once he has said to me somewhat curtly "do you never clean the points?"  Clearly he knew something about the mystique of points!!!!

John

Joe,
with reference to your comment about having the coil connected the right way round can you remembere which way.  Logically I would expect + to be the feed from the battery end an - to be to the distributor ???????????

John

One trick I have learnt whilst being messed about by funny ignition systems is always to make sure you have enough fuel in the tank (obvious really!!!!!).  But sometimes you need more than you think you do to get it to flow over the inlet to the fuel bowl.

When I'm in doubt about whether fuel flow ia adequate I give a whiff of "Easy Start".  If the spark from either magneto of distributor is good it will always fire up regardless of fuel supply.  This way you get a check on the adequacy or otherwise of the spark,and maybe also an indication that there is not enough fuel in the tank.

John

John
Here's a couple possible solutions.
On the magnetos, buy some property in Arizona (very dry climate) and move there.
Second, buy some jersey cows and make Jersey double cream and the MCA can sell it for you. It's a win, win situation. I'm surprised that Gary or Joe hasn't already suggested it.

Steve

Steve,

I could not agree with you more!!!!  I have spent most of my life working in the deserts of the Middle East and I know exactly what you are saying.  Tho' I genuinely love deserts I would not swap them now for our 70 inches a year rainfall in N Wales.  I do have to say that the Arizona desert is one of the prettiest I have been in, the worst being the "Nejd" of Oman which is less attarctive than the moon!

Malcolm in an earlier post related how my orchard GP from Dome Valley started for him as soon as it came out of the container here, then when it got back to my place not long after the Arizona desert dust in the magneto had got damp and that was that!!

Now to get on to the Jerseys I had a large herd of these in Saudi Arabia along with a herd of Holstein Friesians.  I used to scoop the Jeresy cream off the bulk tank in the mornings to put on my Corn Flakes - so thick it actually fell on!.  Never to be forgotten!!!!  The Jerseys are a far superior animal in the heat.  Whilst the Friesians would almost stop breeding in the high summer the Jerseys just kept ticking over.  I've seen Holsteins in Arizona and it is pathetic the amount of pampering thay have to have in the summer heat to keep them going and breeding.

We are hoping to hear of great things from Joe at Baraboo on this cream business.

John

Thought I would show you my best solution so far to the winter damp and magneto problem.  It's effortless and only costs about 2 dollars a tractor.

Simply cover the magneto with an old hessian sack.  Works pretty well but I can't claim 100%.

Why are are magnetos more affected than coil ignitions - are they lower voltage systems?  Joe - you know about these things.

John