Gas-Powered String Trimmers

Well-groomed borders and edges are a landscape's finishing touches, and no tool achieves that faster than a string trimmer. No wonder it ranks second only to the lawn mower in popularity with gardeners. With one notable exception--around trees--trimmers are safe to use for cutting grass or weeds along virtually any edge in your garden: sidewalks, curbs, stepping-stones, planted borders, and fence lines.

There are two basic types: gasoline- and electric-powered. Electric trimmers are lighter, simpler, and quieter but are limited in power, versatility, and often, cord length. Gas trimmers suffer none of those weaknesses, and many accept a variety of attachments for more specialized jobs; but they are noisy and consume gasoline. Because of their greater versatility, most gardeners choose gas-powered trimmers. Hundreds of models in a range of prices are available.

Trimmer Basics

At the business end of the trimmer are the head and the monofilament line that spins from it. A shaft delivers the engine's power to the trimming line, and of course there is the engine, often with a clutch.

Line and line heads. To cut, all string trimmers use rapidly spinning monofilament line, and its flexibility offers a degree of safety unmatched by bladed trimmers. When the string hits anything hard, it doesn't break or chip; it just wears away slightly and more is fed out. How fast the line wears depends upon its thickness and the material it's hitting.

This monofilament resembles a heavy fishing line, and its diameter is one way trimmers vary. Thicker lines don't necessarily cut heavier growth, but they cut faster and are more durable. As line weight increases, engine power must go up, too--it takes more power to spin a heavier line.

Most heads spin a single line, but some have two lines, one from each side. More engine power is also required for two-line heads, which cut faster (but usually not wider) and vibrate less than single-line ones.

Line-advance systems come in three types: manual, tap-to-advance, and automatic. Manual heads, the most basic, require that you turn the engine off, then advance the line by hand. This type of trimmer is all but extinct. Tap lines are better; bumping a spring-loaded knob on the ground advances the line. Automatic is most convenient and costly. It works by sensing the increase in rpm as the line wears and gets shorter, then releasing line until the rpm return to normal.

However it's advanced, the line eventually runs out and needs replacing. Some heads employ easy-to-use pop-in replacement spools, while others require some disassembly and hand-winding.

Power shafts. Shafts come in three basic styles: straight, curved, and split.

Straight-shaft trimmers offer the most power, comfort, and flexibility. Their shafts are longer, which gives them more reach for easier cutting under shrubs and fences. Reduction gears lower the spinning speed and thereby increase the power to the line.

Most straight-shaft models have two-line monofilament heads that take wear-resistant 0.095-inch-diameter line.

Many straight-shaft trimmers have solid steel driveshafts supported by vibration-reducing bushings. Others rely on flexible drive cables in plastic liners. Both are reliable, but solid driveshafts are smoother and more durable. If you plan on cutting heavy brush with a blade, favor units with solid driveshafts.

Curved-shaft trimmers are the lightest and most economical. They deliver power to the cutting head by a flexible-cable driveshaft. They are perfect for trimming around flower beds, fences, and paths found on a typical city lot.

The more powerful units employ dual-line heads. Gear reduction is not possible on a curved-shaft trimmer so the head always spins at engine speed.

Curved-shaft models are shorter than straight-shaft models, making them easier to store and transport. But, if you have to bend your back for the trimmer to reach the ground, it may be too short for you.

Split-shaft trimmers take straight-shaft utility one step further. The two-piece shaft accepts various attachments such as a blower, blower vacuum, cultivator, edger, hedge trimmer, pruner, and even a snow thrower. Changing attachments is as easy as pushing a button or twisting a knob.

Engines. Nearly all gas-powered trimmers have electronic ignition systems and primer-type carburetors to make starting easier. Most gas-powered trimmers rely on two-stroke engines, but a few four-stroke overhead-valve models are available.

Two-stroke engines are simpler and lighter, produce more power for their size, and can operate in any position, even upside down. Their disadvantages are relatively high fuel consumption, greater exhaust emissions, and the necessity of mixing oil with the gasoline.

Four-stroke engines are rare on string trimmers but promise to become increasingly significant. They are somewhat quieter and cleaner, and they use their unmixed fuel more slowly. They also have more power at low speed. But compared to two-strokes, they suffer from slower throttle response, greater mechanical complexity, more weight, and frequent oil-check maintenance.

For gardeners who like the four-stroke's environmental advantage but prefer the two-stroke's utility, new, low-emission two-strokes are now entering the market. Two manufacturers, Tanaka and RedMax, have unveiled designs that will meet the most stringent small-engine emissions requirements.

Trimmer engines fall into two performance categories: those with single-counterweight crankshafts, and those with dual-counterweight crankshafts. As a rule, single-counterweights are less expensive.

If you prefer premium tools, look for dual-counterweights. They run smoother, are more powerful, last longer, and are more expensive, but their higher quality makes repairs easier and more cost effective.

Engine size in cubic centimeter cylinder displacement (cc) is another way to compare engines. Though greater displacement generally translates into more power, in the range of engine sizes used for trimmers that's not an absolute. In practice, a 23-cc engine might outperform a lower-quality 30-cc engine. Horsepower would be a better way to compare engines, but manufacturers seldom publish those ratings.

A clutch is another indicator of trimmer quality. A clutch disengages the cutting head when the engine idles. On clutchless trimmers, the cutting head never stops spinning. To check whether a trimmer has a clutch, pull slowly on the starter rope. If the head spins, there is no clutch.

Attachments

The choice of attachments for your trimmer depends on the model you select. Generally, curved-shaft trimmers accept few, if any, attachments. Most straight-shaft models are more versatile, though you may need to buy extra components. If you plan on using a blade for some jobs, save money by choosing a model with a blade conversion kit. Several other attachments are available, such as fixed-line (non-advancing) heads with extra-heavy line; plastic blades; and a wide range of steel blades designed for cutting grass, brush, and wood. If you have a large or rural lot to maintain, the more accommodating straight-shaft model is the best choice.

Safety Concerns

Eye protection is a must, and ear protection is highly recommended. Gloves and heavy shoes are a good idea. If you buy a blade-capable model, your trimmer will come with bicycle-type or extended "J" handlebars and a harness. Never install a hard blade without the proper hardware.

Never use a string trimmer to cut grass around the base of a tree, especially thin-barked young trees, which can be damaged easily.

Shopping Tips

Some trimmers are more user friendly than others. For instance, a translucent fuel tank makes it easy to know when to refill, and then do it without spilling. On some engines the air cleaners or spark arrestors are buried or difficult to reach for maintenance.

It's hard to beat the national hardware and home center chains for bargain-priced trimmers and brush cutters. However, if you buy from such a place, be prepared to assemble the unit and diagnose for yourself any difficulties that arise.

In terms of value, a local servicing dealer may have the edge. Dealers offer a wider and often better range of equipment and can help you make the best choice. They have the technical know-how, parts, and accessories to custom-equip your trimmer and keep it running. As well, they'll set it up and adjust it, assuring easy starts and optimum performance right out of the box.

26 gas-powered string trimmers

These trimmers represent the range of choices for homeowners with average to large suburban or rural properties to maintain. All feature 20- to 30-cc engines so share roughly equivalent capacity. All but the Honda and the Ryobi 975r are two-stroke. Prices range from $70 to $373.

Echo (800) 432-3246

Model GT-2000; $160

9.3 lb.; curved-shaft, cable drive. Engine 21.2 cc; clutch. Line diameter 0.080 in.

Model SRM-2100; $220

11.4 lb.; straight-shaft, cable drive. Engine 21.2 cc; clutch. Line diameter 0.095 in. Blade capable.

Model SRM2400SB;$330

12.4 lb.; split-shaft, cable drive. Engine 23.6 cc; clutch. Line diameter 0.095 in. Blade capable.

Efco/Olympyk (800) 447-1152

Model 8726TA; $280

12.6 lb.; curved-shaft, cable drive. Engine 25.4 cc; clutch. Line diameter 0.095 in.

Model 8725LAV; $290

10.9 lb.; straight-shaft, solid drive. Engine 25.4 cc; clutch. Line diameter 0.095 in. Blade capable.

Green Machine (704) 588-3200

Model GT25; $309

11.5 lb.; straight-shaft, solid drive. Engine 24.5 cc; clutch. Line diameter 0.095 in. Blade capable.

Homelite (800) 725-9500

Model TrimLite; $70

9.3 lb.; curved-shaft, cable drive. Engine 25 cc; no clutch. Line diameter 0.080 in.

Model db825sd; $155

11.7 lb.; straight-shaft, cable drive. Engine 30 cc; no clutch. Line diameter 0.095 in.

Honda (800) 426-7701

Model UMK431LNA; $349

14.8 lb.; straight-shaft, solid drive. Engine 31 cc; clutch. Line diameter 0.095 in. Blade capable.

Husqvarna (800) 487-5962

Model 225RJ; $360

12.1 lb.; straight-shaft, solid drive. Engine 25 cc two-stroke; clutch. Line diameter 0.095 in. Blade capable.

Jonsered (800) 447-1152

Model GT26L; $220

11.5 lb.; straight-shaft, cable drive. Engine 24 cc; clutch. Line diameter 0.080 in.

Makita (800) 462-5482

Model RBC251; $373

9.1 lb.; straight-shaft, solid drive. Engine 24.5 cc; clutch. Line diameter 0.095 in.

Maruyama (425) 885-0611

Model BCL2250; $250

10.3 lb.; straight-shaft, solid drive. Engine 22.5 cc; clutch. Line diameter 0.095 in.

Model MC2300; $360

10.6 lb.; split-shaft, solid drive. Engine 22.5 cc; clutch. Line diameter 0.095 in. Blade capable.

McCulloch (800) 421-9917

Model Mac1385J; $160

11.8 lb.; curved-shaft, cable drive. Engine 32 cc; clutch. Line diameter 0.095 in. Blade capable.

Model Mac3227; $200

14 lb.; straight-shaft, cable drive. Engine 32 cc; clutch. Line diameter 0.095 in. Blade capable.

RedMax (800) 291-8251

Model BC2300DL; $370

10.2 lb.; straight-shaft, solid drive. Engine 22.5 cc; clutch. Line diameter 0.095 in. Blade capable.

Ryobi (800) 345-8746

Model 725r; $119

10 lb.; curved-shaft, cable drive. Engine 31 cc; clutch. Line diameter 0.080 in.

Model 975r Trimmer Plus; $209

13.8 lb.; split-shaft, cable drive. Engine 26 cc; clutch. Line diameter 0.080 in.

Shindaiwa (800) 791-8647

Model 22F; $160

9.3 lb.; curved-shaft, cable drive. Engine 21.1 cc; clutch. Line diameter 0.080 in.

Model T230; $248

9.7 lb.; straight-shaft, solid drive. Engine 22.5 cc; clutch. Line diameter 0.095 in.

Stihl (800) 467-8445

Model FS36; $140

10.8 lb.; curved-shaft, cable drive. Engine 30.2 cc; clutch. Line diameter 0.080 in.

Model FS80; $330

11 lb.; straight-shaft, cable drive. Engine 25.4 cc; clutch. Line diameter 0.095 in. Blade capable.

Tanaka (253) 395-3900

Model TBC2510; $300

11.8 lb.; straight-shaft, solid drive. Engine 24 cc; clutch. Line diameter 0.095 in. Blade capable.

WeedEater (800) 554-6723

Model Twist n' Edge; $100

10 lb.; curved-shaft, cable drive. Engine 21 cc; no clutch. Line diameter 0.065 in.

Model FeatherLite SST; $100

8.3 lb.; straight-shaft, cable drive. Engine 21 cc; no clutch. Line diameter 0.065 in.

Ken Morrison is a garden power equipment specialist living in Anacortes, Washington.

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