You ask we answer. Here's the latest in our "Ask a Mechanic" series.
Q: How come service intervals for my dirt bike are measured in hours and not miles like my car?
A: Dirt bikes and ATVs were originally considered "equipment" rather than the fun all-terrain vehicles we enjoy today. On equipment, maintenance is measured in hours with an hour meter as you are not really traveling miles, but likely idling for long periods doing work or whatever is required of the tool/equipment. So, time on mechanical equipment came to be used as a standard for maintenance measurement prior to people using mileage on vehicles. That measurement then was adopted into the ATV and off-road world.
Mileage as a measurement and the odometer was adopted as streets and highways were built. The odometer was actually not designed for tracking maintenance and wear but rather for navigation of the road and highway systems in conjunction with maps and mile markers. You can probably find early vehicles with both an hour meter and odometer. Just because the engine is running doesn't mean it's been moving thus the wear and maintenance on other items like suspension, brakes, and tires for example, is different.
In many respects, an hour meter and an odometer would be useful on most vehicles today with all the traffic. A short commute to work mileage wise can still take a couple hours and that's time burning fuel in an engine even if not under a heavy load. One might even argue that its more wearing on an engine to stop and go from idle than to cruise and that factor alone makes mileage a somewhat inaccurate way to judge wear and maintain a schedule of maintenance with a high degree of accuracy.
Traditionally though, street legal vehicles have odometer while strictly off-road has an hour meter.
Lucky for the ATV and Dirt Bike world companies like Trail Tech make some cool odometers that function as hour meters, and even incorporate GPS navigation and other cool features to help maintain service schedules, judge wear, and even navigate. Need one for your ride? Check out all hour and tach meters.