1950 Cub no start under 40 dergrees

[28plymouthman]

I have owned this tractor for years. The last two or three years it will not start when it gets cold. It is 6 volt and cranks fine. It gets plenty of gas.
I have rebuilt the mag this summer hoping it was the issue. Last week I put a 12 volt battery booster on it to give it some extra help and it eventually started. After it warms up it is fine. What could be the issue.

[Slim140]

How old is the gas in it? Have you changed the spark plugs recently? Have you done a compression check on it?

If you have good fuel, fire, and good compression, 6V should start it fine.

[lowgearfarm]

Are the spark plugs wet or dry when pulled after prolonged cranking and no start?
If dry, look to the carburetor (or other fuel issues). If wet, look to the spark.
And whether you get it going or not, knowing the results of a compression test is always part of due diligence.

[inairam]

Do you use a multi-weight oil? I find that helps with cranking.

I use a blue stable marine-grade fuel additive. It supposes to have enzymes that eat the alcohol while reduces the chance it will absorb water

Check the bowel under the tank and the air filter. I pulled oil /ice donuts out of the air filler bowel

Sometimes some heat on the carb/ manifold helps.

If it cranks fine, that ( means your cables are the correct size) and you just rebuild the mag ( assuming you replaced the spark plugs as well) the only thing left is the fuel. Maybe tweak the timing a little. You can still rotate the mag a little after machinal timing it.

My 6 volts with mags need choke in the winter but not in the summer

[Gary Dotson]

Have you checked for proper choke operation? Sometimes the choke arm will slip on the shaft causing the choke to not close fully.

[tst]

do a compression check, even a tired engine will run decent, when they get cold weak compression can cause hard starting, take the air intake hose off the carb and make sure its not restricted and that the choke is working

[28plymouthman]

A lot of good ideas to check on. The fuel is new . The battery cables are the big 0 or #1 size. New plugs. I will check the plugs after cranking for wetness. The choke has to be pulled all the way . I will check compression . I haven't checked the timing. Will do that. Thanks all for the info.

[ShawnAgne]

Mine is similar in the cold. In a previous thread I asked about an magnetic oil pan warmer. Someone mentioned using a heat gun 3 or 4 minutes on on the manifold. Tried that the other day helped out. Mine is 12v and just sputters a lot when cold and needs a lot more choke. When i ts warmer barely have to hit the starter and it goes.

[Scrivet]

...... The choke has to be pulled all the way .........

Just because you're pulling the choke rod all the way out, doesn't mean the choke valve is completely closing off the intake. That's what Gary is talking about here.

Have you checked for proper choke operation? Sometimes the choke arm will slip on the shaft causing the choke to not close fully.

I like to have the choke arm positioned at six o'clock (on the IH carb) with it open or normal running. That way, hitting a bump, the weight of the lever and rod can't accidentally close the choke and stall the tractor.

[Glen]

Hi,
Below is a pic from TM Tractor of the engine side of the IH carburetor.

If your choke rod is the original length, the arm on the carb should be about in the position shown, when the choke valve is fully open.
The screw on the arm has to be kept tight, sometimes they loosen, and the arm turns on the shaft.

[DickB]

Well, what works for me is the full belt and suspenders approach. Sparing nothing and treating it tenderly, I heat the oil pan with a magnetically attached heater. The battery is "maintained" full time with a unit hooked to the electric power. And, I inserted a heater element into the casting that goes from the bottom of the radiator (hose inter-connection) up to the top/rear of the engine. The last item was done, briefly, by drilling the right sized hole into the "plug" from casting that's located right next to the hose from the radiator. Threaded that hole and inserted an electrical heater element with the element "sideways" to minimize impeding water flow. I find that oil pan and engine water heating timing is somewhere around 1/2 to 3/4 of an hour and then I start it up. A bit of choke as if it were a spring day. Engine block feels warm to the touch. One pull, sometimes two and I'm ready to go. Don't know if this will work for you but, so far, it has worked for me. With 2' of snow coming at me right now, I'll plug in after wading out through the snow when it's high enough, check the time, and return to plow snow. Hoping this helps a bit.

[Scrivet]

..... The screw on the arm has to be kept tight, sometimes they loosen, and the arm turns on the shaft.

Diving a little deeper on this subject, other potential issues are if the two sides of the clamp side are touching there may not be enough clamping force on the shaft, the knurled portion of the shaft may have eaten away at the interior of the lever making the hole larger and unable to clamp tight enough, the clamping screw can be stripped, the clamping arm(s) can crack.

Not saying any of this is the cold start issue, but if you're gonna check the choke lever might as well be thorough about it.

[Gary S.]

Simple test for that is manually move the choke lever at the carb and see if it starts easier. In the winter I have always stood on the left side of the tractor to start it mostly because I could operate the choke lever far easier than using the rod. Now with preheating the manifold with a heat gun I'm there anyway

[28plymouthman]

Sorry, I haven't been here for a while . the tractor isn't starting this cold. I did hook up a 12 battery to it to spin it faster and it did start. I am currently rebuilding the carb. Wrong parts arrived. Will let you know if it starts easier. Would like to keep the 6 volt system. Thanks for all the suggestions.

[Don McCombs]

Was the 6V battery fully charged when you attempted the start?