Cub hard start

Just wondering why a Cub won't have any problem starting in the warm weather but when it get cold it's almost impossible to start? I choke it and gas comes out of the carb. but it will not start. It is a 6 volt system still. I can only start it if I hook up the battery charger put it on at 125 amps and spray a little starting fluid in the carb. Nice blue spark all the time. I had another Cub that would start right up in the coldest weather even if it sat for months. Any suggestions how to fix the problem? Thank you for your time, Joe

How is the compression / overall condition of the engine? What weight oil are you useing?


Andrew

Joe, you didn't mention if this is a magneto ignition or distributor. If it is a distributor, you may want to check the condition of your battery, and also the points. The ignition coil is a "step up" for voltage. When you crank an engine, the voltage drop on the battery is significant. The lower the voltage going into the coil, the lower the output of the coil. In cold weather, the voltage drop due to higher cranking amp requirements is even greater.

Another thing to check is the plugs and wires. Old wires with corroded contacts, or evern worse, old composite core wires (ie. not copper wire core) require a lot of voltage to fire plugs with a good, hot spark. Also, make sure both ends of the battery cables are clean and making good contact.

An old timer taught me that in cold weather, it is actually better to start a distributor tractor with a hand crank in really cold weather, as you are using the full voltage of the battery. Technique is rather simple. turn on fuel, put choke on, 1/2 throttle, and leave the ignition off. 2 full cranks. Set choke to 1/2 position, turn ignition on. quick crank. Will fire almost everytime, and often will run from there.

on the 72-79 Ford ignitions, they had a bypass wire (brown) that took voltage in front of the solonoid, so the voltage to the ignition was higher. Same concept.

Short recap: check battery to be up to full charge, check all electrical connections, check points and plugs. Sounds like your battery is getting weak, or you have some dirty electrical connections......or both

as always, IMHO.

Choke it one turn then no choke at half throttle.
Try new spark plugs AC Delco work for me.
Tighten carb bolts.
Check for intake leak.
Check compression.
Run it at night in the dark and look for spark arc.

Dell

Hi Joe, SOMETIMES you can get a start and a brief run if you shut off the gas. I do this on a 2N I play with sometimes. Obviously turn the gas on when it starts. Others just crack the gas shutoff to allow a small amount of fuel. If you can stop the flooding by controlling the gas it will help. Check over on the N board for today's posts on this topic. Some very good info over there.

J,Mine does the same thing.Try NO choke and pull out the choke slow as it turns.Mine will fire with no choke and then die a little untill about half,then it all the way in after 30 seconds or so.Just try it,before you start major operation for no reason.

Thanks all. I will play with the Cub tomorrow and try all your tips and tricks. It is a distributor. The battery is only 3 months old. I changed the points about 6 months ago (only drove it for about 2-3 hours since then). I have never changed the plugs. The wires are not arcing out. I use 30W oil. I will also check the compression at some point. Again, thanks to all of you for the help. Joe

Hard starts at times can be a symptom of a vacuum leak. Not allowing the fuel air mixture to reach the cylinders after you have gas running out of the carb. and no start pull the #2 or #3 spark plug.If they are dry then you have a vacuum leak. Also at times the spark plugs can get fuel fouled so you may want to change the plugs or clean them with some carb cleaner. Also the timing may be off a few degrees off