B & S problem on a '73 Gilson tractor

[Anonymous Poster]

B & S problem on a \'73 Gilson tractor

Hi All,

I hope one of you can shed some light on a problem my Dad and I have encountered.

My Dad has a B&S 16 hp engine in his 1973 Gilson S16 lawn tractor. After 27 years of faithful service, it has developed what we believe to be an ignition problem. The spark at the plug is weak to non-existent.

Our observation is that the ignition points are open during the majority of the rotation of the crankshaft, close shortly before the plug should fire and open at the time the plug fires....only to stay open until the cycle repeats.

This seems counter to what we've observed on other engines. That is, usually we observe the points to remain closed during the entire crankshaft rotation and open at the time the plug fires, then close again a few degrees later and remain closed until opening again to fire the plug.

Our question: "Is what we're observing on this engine usual for this model, or other B&S engines?"


We now assume what we're observing on the points is incorrect, and we think that the coil is not getting sufficient time to build up a sufficient magnetic field since the points are closed for such a brief period of time. Although we're not sure why this would happen, it would imply a problem with the ignition points plunger mechanicals.

On the other hand, if this is normal for these engines, then we will assume that the magneto/coil are creating a weak spark.

The numbers for the engine are: Mod #:326434, Type #:0134-02, Code #:7304031, if that means anything to anyone.

Thanks in advance for any help you can give.

Sincerely,

Rick

 

[Von]

Re: B & S problem on a \'73 Gilson tractor

Rick,
You can buy an electronic ignition unit that replaces the points and condenser for that motor for about $10.00. This should take care of your problems.

Von

 

[W5FL]

Re: B & S problem on a \'73 Gilson tractor

The difference you see may be the difference in 2 cycle and 4 cycle engines. The 2 cycle fires each revolution and the 4 cycle fires every other revolution. A problem on many push mowers is they develope severe ignition problems right after hitting a rock or dirt because the flywheel shears the aluminum shear pin (square key between the crankshaft and the flywheel) and then the timing is off too much to run properly. Happens to thousands of mowers each year. Harder to do on a garden tractor because the belts cushion the blow.

 

[Rick Jay]

Re: B & S problem on a \'73 Gilson tractor

Hi Von,

Thanks for replying. We did replace the original points with a new set, which did not help. Replacing with an electronic ignition module is an option, but we're not sure if the plunger that activates (opens/closes) the points is working properly. If that is the case, wouldn't a broken or malfunctioning plunger prevent the electronic ignition module from working properly? I'm assuming the electronic module must be activated by the same plunger, is that correct?

It seems a long shot that something might happen to the plunger, but we're just wondering if what we observe in the operation of the points is normal.

Thanks again for your help.

~Rick

 

[Rick Jay]

Re: B & S problem on a \'73 Gilson tractor

Hi Wen,

Thanks for your insight. The tractor was running fine the last time it was used, so I don't think it's a sheared flywheel key.

My Dad did mention that all this season it's required more cranking than usual to start, which would suggest a weakening coil/magneto circuit. Now it won't start. We just would like to make sure that our observation of the operation of the points is correct for this engine before we rip the engine apart.

Actually, tearing down the engine isn't the hard part, removing it from the tractor will be most of the hard work, so we would like to exhaust all our options for an external fix before we pull the engine.

Thanks again,

~Rick

 

[Von]

Re: B & S problem on a \'73 Gilson tractor

Rick,
The plunger is not used, so that will not be an issue. In fact you get a plug for the hole that the plunger goes in. Hope this helps.

von

 

[Rick Jay]

Re: B & S problem on a \'73 Gilson tractor

Hi Von,

Thanks again for the reply. If the electronic ignition module bypasses the plunger, then that would be a good (cheap) way of determining whether the problem is with the plunger mechanics or the magneto/coil circuit. I'll discuss this with my Dad and we'll probably pick up an electronic ignition unit.

Just out of curiousity, if the electronic ignition module doesn't use the plunger for proper timing, how does it "know" when to fire the plug?

My experience is more with automotive systems than small engines, so maybe my parallels aren't quite accurate.

Thanks again,

~Rick

 

[Von]

Re: B & S problem on a \'73 Gilson tractor

Rick,
I'm not sure how they work, just that they do. I think they may be triggered by the magneto as it spins. Maybe someone can enlighten the both of us on this one! Good luck with it.

Von

 

[KCB]

Re: B & S problem on a \'73 Gilson tractor

A problem that I have found common for B&S engines that are stored in damp locations can be the formation of rust that will prevent operation of the magneto. Check the outer surface of the flywheel and the 2 ends of the coil laminant core (where they approach the flywheel) for rust. Will have to loosen the coil to clean the laminant ends unless the flywheel is removed. If any is found, just sand it off with some fine sand paper.

 

[W5FL]

Re: B & S problem on a \'73 Gilson tractor

Guess the old gasoline engine requires fuel, and compression, and spark, properly timed to run. Grab hold of the spark plug wire and hit the starter...maybe easier to hit the starter and let the spark plug arc to ground through about a .030 distance to see if you have a hot spark or not. If not, points and magneto is about all there is to check. Compression gauge checks compression, and guess you can tell if it is pulling in gasoline by either being wet inside the compression chamber or smell it strongly in the exhaust when it won't start.