Project Lab: Here’s what fixing a broken lawnmower really looks like

Winter can be a great time of year to buy a used lawnmower.

Demand is almost as low as the temperature, at least in southern Wisconsin. A quick search on Craigslist reveals both push and riding lawnmowers available for less than $50.

But acquirers of the cheapest mowers should expect to do some work.

“Runs and works but… THE STEERING IS MESSED UP,” one listing says.

“Could I fix such a machine?” I have often wondered. Most of my small-engine experience has been in the carburetor area. I had never cracked open an engine before, a likely necessity with some of these rusty beasts.

“Would it be practical to fix such a machine?” was a more pressing question in my mind. We often hear that it’s cheaper to buy new stuff than to fix old stuff. But new lawnmowers can cost hundreds of dollars. Surely this might be one area that could disprove the notion.

I got my chance to answer those questions back in April, when I picked a 6.5 HP Toro Recycler push mower up off the curb.

With the help of my retired-nuclear-plant-mechanic father-in-law, Neil, I learned that:

— It is possible to fix up a thrown-away lawnmower for a decent price. Depending on what’s wrong with the mower, your experience may differ. This one had a stripped spark plug hole. You enlarge the old spark plug hole with oversized threads, screw in a threaded insert, and then screw the spark plug into that new hole.

— There are two kinds of commonly-used threaded inserts for small engines: an externally threaded insert, which is a tube with threads on the outside and the inside; and a helical insert, which is a spring that screws into the new threads, combining to make a hole that fits your spark plug. Both types are commonly referred to as “helicoils,” though Heli-Coil is actually a company that sells both types of inserts.

— These two types of threaded inserts are surprisingly affordable. You can pick up everything you need for under $30. Lucky for me, Neil’s friend had a spare Heli-Coil kit sitting around, so we just used that instead.

— These two types of inserts are drastically, drastically different. Neil and I had watched a lawnmower-fixing tutorial that demonstrated the use of externally threaded inserts, which basically install with a screwdriver. But the Heli-Coil kit we had used spring-type inserts, which install using a combination of threaded rod, threaded shaft and swearing.

— Seriously, Rube Goldberg’s German-engineer cousin must have designed those things. With two wrecked inserts down and only one remaining, we got it right. If you go the helical insert route, make sure you have extras.

— The rest of the process was pretty easy. The head cover was ridiculously simple to take off and put back on. The only other thing I needed to buy was a head gasket for about $15.

Once everything was put back together, the mower started on the fourth pull. It mowed like a champ. It now is on long-term loan with my friend Adam, who offered me his fancy unused Internet router in exchange.

Saving that old mower from the trash turned out to be doable— and a great deal.