1972 Standard Cub won't start after restoration

[NCFarmer]

Hello all. I am new to this site. I have a 1972 standard cub that was bought new and has stayed in our family. I parked it last summer after garden time and went to start it 3 weeks ago and nothing. So I went and completely tuned up the ignition system. Also replaced voltage reg, and completely rewired the whole tractor front to back. I am getting spark to the plugs via an inline test light but it will not fire off. The 12 volt cubs flood fast if they don't start quickly. I do not understand why it will not start. It has not had the distributor out or moved, it won't even hit off of ether, (used very sparingly). I do not use ether unless it is a last resort. I have rebuild carburetor, fuel flow from tank is excellent. I do not understand. Anyone have any ideas? Garden time is coming soon and I need it operating.

[inairam]

Have you tried some starter fluid in the intake of the carb?

If you have spark and it kicks with starter fluid then it is a fuel problem.

[NCFarmer]

I tried starter fluid sparingly and it hit one time and will not hit after that. I have a 140 and a 656 that I use regularly and they all function similarly so I am familiar with ignitions and carbs but this one would see straight foward. It has to something simple I am overlooking. I will go back and re-check the carb rebuild and see what happens. Thank you for the reply.

[Waif]

Spark plug health? Do you have a fresh set properly gapped to try?
Wetting them heavy with gas can end a starting process till dried.
Plug gap can be vital too. (Been there!). And of course proper wires ,wire routing , and wire condition.

When carb flooding is a concern , just shut the gas off and use the fuel in fuel line for a starting attempt.
A Cub as you know is subtle when we are listening to it try to start. When flooded and gas is flowing onto the ground it is shut off fuel and take a break time. (After safety precautions regarding explosive fuel vapors are addressed...)

The quality of your spark matters.
Compression may have caused your "pop" on a cylinder when you tried starting fluid.
Use carb cleaner instead. It burns fine and is not as much a risk of burning too hot.

Did you check your main jet to be sure it is clean?

[MiCarl]

If it won't light ether it's either got ridiculously low compression or it's not getting proper ignition. I'd throw a new set of plugs in before I even thought about anything else.

[cjack]

You have probably already done so, but if not, double check your spark plug wiring order. My son Spencer had similar problems on the weekend and we were wracking our brains what could be wrong until the engine backfired out of the carb when using carb spray. The wires to #2 and #4 were switched! He was sure he had done it correctly but in the course of troubleshooting all sorts of spark issues the wires got crossed. (I also prefer carb spray to starter spray.)

[NCFarmer]

Thank you for help. I will check spark plugs/gap, and ignition spark quality. I will verify timing and firing order. I will use carb cleaner instead of ether. While I'm at it clean the carb one more time. I am sure it is something simple. Like you said troubleshooting one thing and mess up another unknowingly.

[cjack]

If it's not firing with the ether spray it is likely not your carb.

For cleaning the carb our good neighbor brought us over a jug of this stuff. We soaked the carb in it for 3 hours, with some intermittent toothbrush scrubbing, and all our carb issues disappeared. I liked this stuff because it is safe to handle.

[SONNY]

Take the plugs out, see if dry or soaked, smell like gas? if wet, put in dry ones and go easy on choke. if dry, squirt a bit of gas in each hole, slap plugs back in and go! I have a couple here that do the same thing after sitting. also have 4 orange ones that require this treatment after sitting longer than 30 days! Annoying but I live with it! thanks; sonny

[Glen]

Hi,
If you replaced the points, and set the gap, and know they are good, and know the condenser is good, then I would check to see if you are getting 12 volts at the resistor, and then 6 volts at the coil, when the ignition switch is on. Use a volt meter for testing it. I think those had an external resistor for the coil. It may not be getting enough spark to run.

The ignition switch can corrode inside, sitting, and not let power through. I've had success fixing them, on other machines, by just spraying WD 40 into the key opening, using the little tube to get the spray into the opening. Turn the key back and forth some, and it might work.
TM Tractor at the bottom of the page sells new switches if you need one. There were 2 different switches used in 1972, they changed during the year, the listing shows. You need the serial number of your Cub to know for sure which it is. The switches have different connections on them.

http://www.tmtractor.com/new/el/816fp.htm

http://www.tmtractor.com/new/el/907fp.htm

http://www.tmtractor.com/new/el/708fp.htm

If the switch is good, then the coil might be getting weak, and not making enough spark. The spark should be blue, and jump a 1/4" gap, holding a spark plug wire end 1/4" from a bare metal place on the engine block while turning the engine with the starter, with the ignition switch on. Hold the wire by the insulation.

[ricky racer]

Check compression. You likely have a valve or two stuck open.

[MAGNETO]

Check compression. You likely have a valve or two stuck open.

[Steve Butram]

Do you have gas dripping out of the Carb while the engine is cranking.