How to Break In a New Motorcycle
My name is Ryan and I review motorcycles. Last year I rode 10 bikes through the break-in period, and this is how I do it.
First you buy a new motorcycle in November. Riding season is almost over, Christmas hasn’t started, and the EICMA show just made everything on the floor old news. These motorcycles turn into pumpkins on January 1st, so Cinderella will drop her pants to make a deal.
Next I idle the bike for 5 minutes. This moves oil to the oily parts of the engine, and lets me watch for smoke signals and unusual sounds. Manufacturing defects are rare but if there is one, I’d prefer to catch it from the safety and convenience of a dealership parking lot. Once I’m convinced that I bought an engine rather than a grenade, it’s time for the riveting first ride…
See new motorcycles come with new tires. And while slippery release agents are a thing of the past, I still want to scrub some roughness into the tread before cutting loose. Low-speed figure-8s roughen up much of the tire profile, while also giving me a feel for the bike’s weight, balance and dynamics. More than 50% of crashes involve riders who are new to their machines, so I always get acquainted with fresh bikes in a low-risk scenario.
Once that’s done, it’s time to go for a real ride to break in the engine with real combustion pressure. Whether I do this by riding gently – or riding hard – is an extremely contentious topic. Contentious as it is, hard breakers and soft breakers agree on one thing – the break-in period is about seating piston rings to the cylinder wall.
If this is my piston, separating the combustion chamber from the crank case, then we have oil down here and an air-fuel mixture up here. The piston ring separates the two, but if it doesn’t seal properly we end up losing oil into the combustion chamber and losing combustion gas into the crankcase.
Result: we burn more oil, and lose compression. Meaning we burn more gas, and lose horsepower.
So how do I seal my piston rings to the cylinder wall? From the factory, both have micro-rough surfaces. And when you rub two rough things together, they get smoother and the surfaces begin to match. To form a seal. So on the simplest level, you break in an engine by running it. However, if you exert too much pressure on the surfaces, the mountains on one will carve deep valleys in the other. And when the pressure is released, you’ll get empty gaps rather than a seal. That’s why I never lug an engine during break-in. If the piston is too slow, it can still be compressing when combustion happens. That creates a spike in pressure, carving deep valleys between piston ring and cylinder wall. So I avoid extremely low rpms.
Ok – so gentle break-in is crap, just grab a handful and go?
You can also spin an engine too fast, building up enough friction heat to soften the piston rings. If that happens, the surfaces will warp as they cool. And they won’t match.
Ok – so hard break-in is crap too… I guess I should just cruise at middle rpms for the first 1000 kilometres?
If I stay at 4000rpm for the entire break-in period, I’m only teaching my engine one type of heat and pressure. When I eventually go beyond that, it’ll feel the notch. So the ideal break-in ground is neither mellow cruise, nor frantic racetrack, nor steady highway. It’s a twisty road with occasional spots to pull off. That lets me flex the rev range – from just above the lug line to the redline. I do this for about 10 minutes, then I take a break to let the engine cool down. A chilly November day helps to keep temperatures reasonable. And don’t trust the dash on this one – just because my overall temp is normal doesn’t mean there isn’t a hot spot between the ring and the cylinder.
Once my cool-down break is over, I start varying the throttle all over again. Brisk acceleration and deceleration is the quickest way to heat up tires. Remember that our new treads need heat to get sticky. Meanwhile, upshifting and downshifting puts positive and negative pressure between piston and piston ring. Another crucial factor for making a good seal.
So that’s how I break in a new bike – by using a wide variety of rpms and taking lots of breaks. Never lug the engine by riding too soft. Never overheat the cylinders by riding too hard.
Wait a minute – why does the owner’s manual say to ride gently then?
Probably because if they told everyone to hit the redline, they’d essentially be advising new riders on new bikes to hit mach 10 on city streets.
Lawsuit. Lawsuit. Lawsuit.
Let that be a reminder to us of the risks involved. Every experienced rider is inexperienced on a new bike. The most important rule for breaking in an unfamiliar motorcycle is to stick to familiar speeds, familiar lean angles and familiar roads.
I always do. And a couple thousand kilometers down the road, when I’ve changed the oil a handful of times to remove metal shavings, and my carefully varied RPMs become a little more wild… when the frequent breaks become a little more infrequent, and my new bike becomes less new to me…
Then the break-in period is over. And I ride the thing with no limits. Just to show it what kind of life we’re in for. And just so anything that’s gonna fail, will fail under warranty ;)