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Att 5. Replacing 610759 SSI

Added 30 March 2012

 SSI 610759 Replacement

My 1965 Sears SS12 had an intermittent 610759 SSI ( under the flywheel). I replaced the main capacitor and it still failed but would recover for a while only to fail again. I needed a reliable ignition so I used the automotive conversion above.

Since the 610759 SSI is under the flywheel, the flywheel does not have trigger pins, I added new trigger pins to the flywheel from a kit, Tecumseh P/N 730201.

See Figure 1-18A, TrigPin/Pina.Jpg and Figure 1-18B, PinB.jpg

Figure Att. 5-1



Figure 1-18c shows my lay out for the new trigger pins. On the first pass on the lay out, I located the tall trigger pin on the center line of the block like the OEM configuration for other solid state ignitions. This led to placing the short trigger pin at the edge of the hole in the flywheel for a screw holding the flywheel magnets. So I had to off set the trigger pins 1/2”. Thus when the engine is at TDC, the tall trigger pin is shifted to the left of the engine center line. And, of coarse, the trigger has to be off set with it. See Figure 1-18D, 3Gen759A.jpg. The engine center line is shown in yellow. It would be a good idea to set the engine at TDC and mount the trigger and flywheel to check the alignment before drilling the holes.

Despite my best effort, I have trouble drilling clean holes in cast iron. My set up is shown in Figure 1-18E, 3Gen759C.jpg. My notes show that the correct size drill bit is a # 12, .189”. I picked 3/16”, .1875. for a test hole in a piece of scrap and it fit perfect. I drilled the hole for the short trigger pin and it came out perfect. The drill bit wondered on the hole for the tall trigger pin and the hole came out oversized. I should have drilled a small pilot hole first. If you have to use JB weld for a trigger pin, clamp it in overnight to make sure that the pin is set all the way in the hole and stays there until the epoxy is well set. I am better at chasing electrons than at playing machinist.



Figure 1-18D, 3Gen759A.jpg. Shows the installation of the 3 Generation Trigger and mounting bracket. One immediately notices that the trigger is not in the center and the mounting bracket is crooked. It has to be this way for the sides of the air gap to be parallel. The 610759 SSI most often comes with a Delco Motor / Generator set which cranks very slow. To get the initial spark at the lowest possible RPM, I used a tight air gap, .010 to .012” and an additional 50 turns of wire in the trigger coil.

For installation instructions, See Part 1. tecumseh Ignitions-Part 1, SSI Replacement above.

 While I had the oppertunity I took some RPM measurements. The initial spark occured at 140 RPM. The engine cranked under compression with a 4 year old battery at 463 RPM. Removing the spark plug to release compression, the engine cranked at 513 RPM. The transition to advanced spark was at 673 RPM. It idled at 800 RPM.

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