Plugs and starting

[pfj]

I have a 1949 Cub that is used for moving and launching a 16' boat on a trailer on a gently sloping rocky beach. Generally this tractor runs well but it has, over the years, been hard to start. Over the past month or so I have gone through and straightened out some issues with the fuel line (see recent post "Doing away with a sediment bowl") and the tractor went for a couple of weeks starting easily and running well. This morning the tractor would not start. I do not believe fuel is the problem. The tractor will pop once or twice but not catch and run. I have taken out the plugs and cleaned and dried them twice (they were wet with gas) and when I put them back in the tractor will catch and run for 5 or 10 seconds and then die. I suspect if I can get the tractor through this 5 or 10 second period that it will run fine. I am beginning to wonder if the plugs I am using are wrong. They are NGK AB-6 - a plug I understand to be equivalent to a Champion D21. These plugs have been in the tractor for about a year, but there are not many hours on them.

Any thoughts as to whether the plugs may be part of my problem, or if I would be better served for my use with a different plug?

[John *.?-!.* cub owner]

You did not say what kind of ignition you have, but the first thing I would do is try a set of spark plugs, NGK plugs are good plugs. Your symptoms are similar to a coil that is starting to fail, so that may be your next step, whether it be a magneto or distributor. Most cubs do not require choking to start, but frequently do require it to keep running the first few seconds after starting, so also make sure you are not over choking it trying to start it. Also check for good fuel flow, by removing the plug in the car bottom or removing the jet that screws in the side.

[pfj]

Thanks John. It is a J-4 magneto ignition (you helped me with this 18 months ago).

How long should a set of plugs last? These plugs have been in for only a year and a half, and the tractor really hasn't been used very much.

Earlier today I checked the spark and found the spark to be very good when running, but no where near as evident when cranking. I want to dig into this a bit more tomorrow to make sure I have this right (i.e. good spark when running and poor spark when cranking). Does this also suggest a possible problem with the coil?

[John *.?-!.* cub owner]

Crank it over by hand and make sure you are hearing a click 2 times per round. If not the impulse may not be working. At cranking speed it should deliver a spark approximately 1/4 to 3/8 inch long. How long plugs last depend on several things. Burning oil and occasional use will normally mean a year or two, no oil consumption and quite a bit of work and working hard, 5 to 10 years is not unusual, sometimes longer.