This site is not going to be about racing lawnmowers — but there seems to be a lot of interest in that subject, so I though I’d share the little I know about it. Also, I suppose there are other reasons you might want a faster mower — maybe you just want to get the job done faster.
Anyhow, consider how the racers speed up their rigs, and you can see which (if any) of those techniques you would like to use to make your lawn mower faster. Since this information comes from observations on racing mowers, it mostly applies to riding mowers. You might have a self-propelled mower you want to go faster though — and at least some of these tips might apply.
Push Mower
If you have a push mower, the solution is simple — walk faster. Most of the time, that will get the job done quicker, with only minor loss of quality. Assuming of course your blade is good and sharp, and you don’t go so fast the cuts begin to skip patches.
With one of those old push mowers, you will probably find a speed at which you can cut fast, but still do a good job. If not, the first place to look is at your blade. Try sharpening it. If that is still not enough, and you are looking to run that thing at a trot while still achieving a clean cut, then you can try tinkering with the governor, as we describe further below.
Another consideration is the weight of the machine, which affects how fast you can physically propel it. Modern mowers come with lots of safety features, and I don’t recommend removing them — but that would cut the weight and make it easier to push, so you could go faster.
Somehow, we got along for years before most of these safety features were added, and lawnmower accidents were rare. Usually, when they did occur, they could be attributed to carelessness, or shear stupidity. So if you choose to modify your machine by removing any safety features, be sure not to be careless or stupid.
This might require that you use common sense. Today’s society is so designed that common sense is no longer common, however. Everything is designed to be ‘idiot proof’ so nothing you do can conceivably cause any harm to anyone, nor harm the machine. If you have never exercised judgment, or thought before you acted, then perhaps you are better off leaving all that safety stuff in place and just accept your limits.
Self Propelled Mower
With a self propelled mower, the engine is doing two jobs at once — swinging the blade around to cut the grass, and turning the wheel or wheels that propel it forward. Certainly you need to consider sharpening the blade, if it is not in tip-top condition. And the section below on modifying the governor may also be considered. But with the self propelled hand mower you have another option.
Disengage the propellant system. How you do that varies greatly from one mower to the next, but generally it involves removing several parts. You don’t want to just keep them from working, you want to remove any dead weight that remains, and makes the machine heavier and more difficult to push.
A careful look at your particular machine will probably tell you which parts are strictly for propulsion, and if they can be removed without disabling the cutting function. Take off all the junk you don’t need, and presto-chango you have a push-mower (see preceding section).
Or, if you are too lazy to push, and your question was really how can you make your lawnmower go faster without any physical effort on your part, then there are three options. Those are the same as for souping-up riding mowers for racing: change the governor that limits engine RPM; change the propellant ratio between the engine revolutions and wheel revolutions; and remove dead weight and lighten the load wherever you can.
Racing Riding Mowers
OK, time for confessions. I’ve never raced a mower in my life. Don’t particularly want to either. I have been to races, and talked with the participants to get a feel for the game, but I’m an observer, not a racer. So everything hear is what I’ve heard, rather than practical experience. Hey, I said at the start, that this is a one-page diversion, not the subject of this site!
If you want to race your lawnmower, you should give up cutting grass with the thing — the modifications you make will sacrifice cutting ability, safety and reliability for speed. Duh! It’s a race you eedjet, not accelerated lawn maintenance.
A few people race stock mowers — i.e. those that have not been specially modified. They even sometimes win — though they are at a disadvantage as far as their machine goes. Still, skill is more important than mechanical considerations, when it comes to the finish line. And there is one advantage to racing the stock machine — it rarely breaks down. Most of the racing modifications make the machine faster, but less reliable.
Think of it this way. A lawn mower is a highly optimized system of parts and functions — it is designed to cut grass reliably and safely, while requiring the minimum in skills or effort on the part of the operator. Any change to such a highly optimized system comes at a cost, and reliability and safety are high amongst the things sacrificed to speed. Operating at top speed requires greater skill and more effort. And them durn things won’t even cut grass — cause the blade is one of the first things to go when modifying for racing!
So, if you are determined to race your mower, first remove the cutting blade, you won’t be needing it. Then look at the governor. On most engines, you can change a spring to make it longer, shorter or weaker, and thereby increase the range of potential movement in the accelerator. Some people even remove the governor altogether.
The governor limits the top speed of revolution for the engine. This is to keep from harming the engine, since without the governor it is possible to race it so fast it falls apart or breaks. In most cases, the harm is less obvious, wear and tear that shortens the lifespan of the engine. Your choice to modify or remove that safety feature will not only affect how fast you can go, but how long your engine will last. Again, common sense and good judgment are part of what make racing interesting. A bad call on your part may mean you don’t even finish the race.
Another target for speedsters is the propulsion mechanism. If the wheels are belt-driven, for example, you can change the ratio of engine revolutions vs wheel revolutions by changing the diameter of one or both pulley wheels that the belt rides on. When you do this to increase speed, you are also increasing the strain on the engine and the propulsion mechanism, creating another point for potential system failure. The trick is to take it as far as possible without reaching the breaking point.
Finally, you can increase the speed of your machine by reducing the weight it needs to transport. Yes, you could lose a few kilos off that beer belly. But you can also replace the heavy steel deck and replace it with thin aluminum. Same for other shielding parts. Some extremists even punch extra holes in those parts where possible (and rules often limit that kind of thing), to lessen the total weight. If you plan to race, you need to review the rules for the particular venue to make sure your modifications are allowed.
Most importantly, remember it’s all in the name of FUN. Don’t get so hung up on trying to win, that you lose touch with the process and joy of racing. And if you really want to learn how to make a lawnmower faster — go ask the folks at the lawn mower races who have the experience and know-how to get the job done.