Most stump-grinder frustration isn't about the stump — it's about the rental machine and the ground around it. These are the problems people run into again and again, and how to avoid a wasted rental day.
Dull teeth
Rental teeth are often worn, because every previous renter has hit dirt and grit with them. Dull teeth scrape and throw fine dust instead of biting off chips, so the job takes far longer. Before you leave the yard, ask the dealer when the teeth were last changed, look at the carbide tips, and ask whether a fresh set is available. If the machine is barely cutting, dull teeth — not the engine — are usually why.
Hidden rocks and metal
Buried rocks, old fence posts, rebar, and nails are the fastest way to chip teeth and can cause a violent kickback. Rake back the soil and mulch around the stump, probe for anything hard, and clear the surface first. Hit something metal and you're often looking at a new set of teeth and a second trip to the rental counter.
The engine won't start or bogs down
Hard starting on rental gear is usually stale fuel, a clogged carburetor, or a fouled plug — confirm the tank has fresh fuel before you tow it home. Bogging down and stalling mid-cut is almost always because the cutting wheel is being lowered too deep, too fast: take shallow passes and let the wheel do the work (see how deep to grind a stump).
Overheating
Long, heavy, continuous cuts with blocked cooling fins or low oil can overheat the engine. Work in passes, keep the chip pile cleared from the head, and give it a moment between hard cuts.
Not sure the rental headache is worth it for your yard? Compare the options in rent a grinder or hire a pro?, or find a local stump-grinding service near you.