Hard cold starting SC

fixerupper

Well-known Member
I did some work on an SC that was converted to 12 volts. It has a Case mag. The starter really spins it over. When it's warm it pops right off. When the temp is below 30 or so it will tend to flood but eventually will start. When the temp is in the 10 degree range it's a no go, cranks but won't start. After it starts it purrs along better than most SC's Ive been around.

I just delivered it to the customer today so it's gone now, but I just got to thinking, do you suppose the starter spins it so fast the impulse isn't engaging? Have any of you seen this happen?
 
(quoted from post at 19:07:36 01/19/18) I did some work on an SC that was converted to 12 volts. It has a Case mag. The starter really spins it over. When it's warm it pops right off. When the temp is below 30 or so it will tend to flood but eventually will start. When the temp is in the 10 degree range it's a no go, cranks but won't start. After it starts it purrs along better than most SC's Ive been around.

I just delivered it to the customer today so it's gone now, but I just got to thinking, do you suppose the starter spins it so fast the impulse isn't engaging? Have any of you seen this happen?
Or maybe the impulse isn't working but it has enough spark at the fast cranking speed to start it when it's warm? The mag has a few dents on the side of it like someone has rapped on it to try to shake something loose.
 
I have a 52 DC with Case mag. Tractor has been converted to 12 volt. Starter speed does not seem to affect it. If the SC NEEDS to start in cold weather it needs a lower radiator hose heater. The gas is just not atomizing in the cold air of the intake manifold or within the cylinders. A trick I've used on the DC is to take a propane torch and warm the intake from the carb up to the manifold. Does not seem to matter how cold it is, it will start after doing that. But if I don't do that it will very easily flood, just as you described the SC. gobble
 
I've 2 SCs I use on my farm. I heat with wood, work in the woods in winter with no problem. The oldest
non live power one runs a pto wood splitter. Driveshaft turns a graintruck hoist pump etc etc. Both
start flawlessly at 20 below. They sit out on the hill will I store my wood. A 12volt battery will spin
a mag to fast. The impulse will not be working and you'll have a weak spark. I figured that out 40
years ago back in the 70s. Went to distributor and GM alt (not the 1 wire one) on both tracdors and have
never looked back. Don't kid your selve. If you want to use the tractor rather than look at it and you
want 12 volts put a dist on it. That is the problem
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Best bing I ever did was put a distributor on my SC. It’s still 6v but it will start at zero for sure with a well charged battery. I haven’t tried to start it at below zero temps though.
 
(quoted from post at 03:07:36 01/20/18) I did some work on an SC that was converted to 12 volts. It has a Case mag. The starter really spins it over. When it's warm it pops right off. When the temp is below 30 or so it will tend to flood but eventually will start. When the temp is in the 10 degree range it's a no go, cranks but won't start. After it starts it purrs along better than most SC's Ive been around.

I just delivered it to the customer today so it's gone now, but I just got to thinking, do you suppose the starter spins it so fast the impulse isn't engaging? Have any of you seen this happen?

The magnets in these old magnetos get week with age, and people that used to rebuild magnetos are disappearing. That, and if a coil goes bad in one your pretty much sunk. It would probably be best to install a distributor and put the magneto on a shelf.
 
When I was a kid over 50 years ago Dad's SC had to run every day to pull the manure spreader. 6 volt only and it would run at -20. The
impulse spring spins the mag faster to give a spark on a slow turning engine so 12 volt speed should not matter as the mag is spinning faster
than the impulse spring would spin it anyway. Have got a couple Case mags working the last couple days by cleaning them up, both points and
connections. Hang in front of the shop furnace with the cap off to get the moisture out...both jump a 3/4" spark.
 
If mine will just turn over two maybe three times they are running ( and by this I mean clicks of the mag) no need to spin them all are running Case mags,, I have started mine down to -20 no issues no htr no either, and sitting outside,, uncle tells of starting his SC to feed in the 60's when it was -65 air temp,, no trouble at all, things do have to be right though and have good high octane fresh fuel in the tank, the garbage they sell now in the lower grades of fuel is a joke
cnt
 
My Dad used to say, "Let the Mag do the work". Meaning, don't try to spin the engine, pull it over slow, as Case Nutty describes. Yes, I would say the 12V is spinning the engine too fast as this complaint you mention is not uncommon. I would never, ever convert an SC to 12V. With proper size battery cable, no smaller than 1 gauge, and clean connections, 6V does a wonderful job. A DC with high dome pistons is another story.
Obviously the spark plug wires on the SC need to be real copper core and not the "Silicone" or "Radio Suppression" wires. The best plug to use on the SC is Autolite 437, which is extended tip, non resistor. Check those 2 things out.
 
I have two SC tractors. One is a late 1941 fuel burner 12 volt
with distributor. I bought it that way. The other one is a 1948
gasoline with Case mag and six volts. The six volt tractor
starts easier and faster than the 12 volt tractor.
 
What kind of spark plugs to do have in it? I had similar problems with my 311 until I switched to Autolite spark plugs. Be careful, you may end up with a bunch of unburned fuel
in the oil pan.
 
You mention a mag and conversion to 12 volts. Did the conversion use a distributor or was it a modification of the old mag? That makes a difference. Timing changes with the impulse.

Here's just another data point. I have a DH that will not start with the crank for the first start of the day. I've added a starter and a 12 volt battery but still have the mag. When I start
it, you can hear the impulse unless it's spinning too fast (and it's a noticeable noise I listen for during starting). If I spin it faster than the impulse engages it will not start so I hit
it with short bursts on the starter and it fires up in 2 or 3 bursts.

This one has the recommended autolite plugs from John Saeli, the proper plug wires, new rings, valves, intake gaskets and I've been through the carb numerous times. I'm not a weak lad but
I've never had good luck cranking it manually unless the engine is warm (and this is Arizona so "warm" means "close to operating temperature"). The starter works fine unless you spin it too
fast for the impulse and that's how it is.

Why is it this way? It may be that it's never been worked hard enough to seat everything after the overhaul, and I don't have a way of doing that.

Ken in AZ
 
I don't see what difference speed of the magneto makes. When testing I turn them with a cordless drill and if all is good they easily jump a 3/4" spark at that speed. The impulse coupler was to speed the mag on a slow turning engine.
 
We had an electric shop where the owner had adapted a distributor scope to drive a mag. he wasn't satisfied unless that mag had a spark at least 3/4 of an inch when running and 3/8 on the impulse. Claimed case mags were the hottest he worked on. In the forties he said he ran one on a midget racer.
 

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