It was the damn switch!

I was out cutting the lawn yesterday with the 1978-79 Lawn-Boy 7025 when half-way through the backyard it killed. The engine shut down just as if the ignition switch was turned off. It didn't lean out as if it was running out of gas or if the carb has become blocked. Besides checking the gas tank valve and knowing that it couldn't have run out of gas, I feared the worst...a dead coil pack, which is fairly common among these old Lawn-Boys.



I got this mower for free when I saved it from the scrap several years ago. When I got it home, I put gas in it and it started right up. It was bone dry, so bad that gas leaked from the gas tank valve for awhile before it swelled back up. I used it as-is for a few years after getting it, it ran just fine so I left it alone. It would normally start with just one pull. I liked how light in weight and easy it was to just flip it around and maneuver. A few years ago while cutting, it suddenly opened up and surged to full speed, turned out to be the forked end of the air vane broke letting the throttle/choke plate to fall off and open right up. Parts for these old things are still surprisingly available, ran up to the hardware store and picked up a new air vane for something like $10. Throughout last year, the performance of the engine was rapidly tanking, it was losing power, easily bogged down, running too rich and the lower crank seal was leaking. Spent another $10 for a carb kit and a pair of crank seals. It probably never had its carb overhauled before. Replacing the crank seals without the *special* Lawn-Boy extraction and seating tool was fun. I had to drill a series of small holes in the casing of the old seals in order to get a grip on them. The new seals were seated using a piece of heavy PVC pipe. It was a big improvement in performance, it ran great for the rest of the summer and fall.


Signs of a bad seal. Loss of crankcase pressure and the possibility of sucking dirt up into the bearings is a good reason to get this taken care of right away.




Also cooked the muffler baffle while I had it off.

Anyway, that was all last year. This year, it started right up after sitting all winter. It ran like a champ! Used it a bunch to chew up leaves pulled from the garden and clean up the yard. When it died yesterday, I checked for spark using a few tests, none showed spark. I was worried that it could be the coil pack. They're not the cheapest and the new aftermarket ones supposedly have just as high of failure rate (if not more) as the old ones. I'd probably just park the mower and wait for a parts machine to pop up somewhere/someday. These solid state coils require an additional connection to the ground in order to operate. Unlike most other engines where the switch shorts the coil to stop the engine, the switch on the Lawn-Boy has to be in the closed position for the engine to run and it stops when the switch is opened. I pulled off the shroud and started to poke around with my ohm meter, sure enough, the switch tested open. I removed the switch and took it inside to disassemble it.


Opening it up revealed that a wire broke off of one of the contacts. The wires were basically just pressed onto the contacts, no solder or other mechanical means of attachment. Surprised the switch lasted this long.


I cleaned it up inside, replaced the loose wire as the insulation was damaged and soldered the wires to the contacts. I reinstalled the switch and it started right up!



Its a fun little mower, they sure don't build them like this anymore. Some people absolutely hate Lawn-Boys and some people love them. It's not uncommon to see someone pushing a 40+ year old Lawn-Boy around their yard, these things seem to run forever (that is after sorting out these relatively simple problems). Just the other day, I saw someone using an old 60s "bricktop" Lawn-Boy.

We have a newer Craftsman self-propelled walk behind and a Craftsman tractor, so I could use those if the Lawn-Boy had to be taken out of service. I like using it though so I would probably end up finding a coil for it rather quick if that was the problem.