ATV-TALK A Motorsport Podcast · Leonard Duncan

SHOP TALK with Leonard Duncan: "Why Engines Fail – Top 5 Mistakes You Can Avoid"

November 11, 2025·57 min·5 clips

Leonard Duncan reveals why human beings are the number one killer of both two-stroke and four-stroke ATV engines.

Engine failure gets talked about plainly here. Leonard Duncan frames it the way it tends to show up at the shop, with somebody saying the machine was running perfectly before something changed. That detail does a lot of work. He separates a failure that seemed to happen all at once from one that had been building for a while, because that is how he wants riders to think before the damage is done. Prevention is the point. The episode is less mystery story and more hard-earned shop sense about the ordinary choices that decide whether a motor lives. A gasket is not only a small part in his telling. Duncan uses the cheap gasket example to show how saving a little up front can turn into a much bigger bill if other engine parts get hurt. The money talk stays blunt. A crank, piston, head, or four-stroke motor can push the cost into thousands when the damage goes far enough. Two-strokes are cheaper, mostly, but he does not let them off easy. The wrong piston, a bad break-in, or cheap fuel can still make the bill climb fast. Fuel takes the hardest hit. Pump gas gets treated as cheap fuel, bad fuel, and a shortcut he says he has warned riders about again and again. The tone feels like a builder repeating the point because he knows people still try it. Elevation tuning becomes another practical lesson. Duncan says most people do not understand it, then ties his own feel for it to running machines at higher elevation, in heat, and in cold. That is where the episode is most useful. It is about thinking before the weekend instead of explaining the failure after the motor is already hurt. Listener questions are invited, and Duncan leaves room for more shop talk if riders send in what they want covered next. The whole thing stays hands-on: engines often fail from ordinary decisions stacked together, and the cheap choice can be the one that costs the most.

As heard by us

A direct ATV Talk guide to the habits and mistakes that can lead to expensive engine failure.

Leonard Duncan centers this ATV Talk episode on engine failures and the practical habits that help prevent them. He moves from two-stroke to four-stroke examples, then ties in the damage that can come from bad parts choices, weak break-in habits, cheap fuel, and tuning mistakes.

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Why you'd press play

When you want the expensive mistake list before your engine pays for it.

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