A Briggs & Stratton Solid State Ignition Conversion

This post is an accompaniment to my post about an ancient MTD reel-type lawnmower.

That machine's engine had no ignition coil when it was obtained. Here's a view of the engine with its coil missing.

The air-vane governor is there in disarray, but there's no ignition coil.

The 2.0 HP engine's model/type/code number is 60102 0294 01 690801. According to "Chilton's Guide To Small Engine Repair Up To 6 HP", the first five digits of that number signify the following:

6 = 6 cubic inches displacement.

0 = basic design series [whatever that means].

1 = horizontal Vacu-Jet carburetor.

0 = plain bearing.

2 = rewind starter.

The engine predates solid state ignition. Here's a view of its breaker points and condenser, resident under the flywheel.

- - -

The Replacement Coil -- THURSDAY, DECEMBER 27, 2018

The Briggs & Stratton part number for a solid state ignition coil for this engine is 591420. That part renders the points and condenser immaterial to the engine's operation. (I'll be leaving the points and condenser in place, though. I'm unsure of how the pushrod is to be dealt with in the event that the breaker points are removed. So, rather than invite trouble, I'll just leave the breaker points alone.)

My son ordered a Chinese equivalent to P/N 591420 from Ebay, and it just arrived the other day. Here are two views of the coil.

Some notes on the coil:

• The spark plug lead is remarkably long -- almost twelve inches.
• The spark plug connector is a bit iffy. It's very easily dislodged from a spark plug's terminal.
• The curvature of the pole piece ends is odd; they appear to be meant for a much larger diameter flywheel than the one on my engine.
• There's no provision for the governor bracket's upper fastener. The governor will be attached only at its lower fastening point.
• The kill switch terminal takes a 3/16" spade terminal.

With that out of the way, we can proceed to install the coil.

- - -

Kill Switch Wiring

The original kill switch wiring scheme has a wire from the kill switch to the condenser, then another wire from the condenser to the coil. That arrangement needs to be bypassed by a single wire from the kill switch to the coil. If you use the original kill switch wiring, you'll have the breaker points in the kill switch circuit interfering with the coil's operation.

 - - -

Mounting The Coil

I discovered that it matters which way around the coil is oriented.

The first time I installed the coil, I had it oriented so the kill switch terminal was outboard. I had spark, and the engine started and ran for a minute or so. Then, the engine quit and refused to restart. I'd get the occasional puff out of the carburetor, which suggested a timing problem. I unfastened the coil and put it back on the other way around (kill switch terminal inboard). The spark appeared to be stronger, and the engine started readily and now runs fine. Here's a view of the correctly installed coil.

Note the mismatch between the curvature of the coil's poles, and the curvature of the flywheel's perimeter. Note also that the governor bracket is fastened only by the single screw at the bracket's lower fastening hole. Neither of those conditions appears to present a problem.

Coil Air Gap Adjustment

See this post for a relatively easy way to make the air gap adjustment.

Governor Linkage

Here's a view of the correctly assembled governor linkage. (The governor spring is Briggs & Stratton P/N 691785. The spring that was originally on the engine was somebody's kludge.)

- - -

And there we are. I've now got a working engine whose breaker points won't need periodic servicing.

# # #

FEEDBACK

# # #