Busting The Engine Break In Myth | MC Garage

How to break-in a new engine is an extremely contentious topic. In this video from the MC Garage we bust the engine break-in myth by building up two engines, breaking them in using drastically different methods, and then tearing them down and comparing the components at the heart of the discussion.

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Getting a new motorcycle is an exciting prospect, but once you fire it up for the first time you’re left with what many deem a great responsibility: breaking in that new engine. What is engine break-in? Fresh from-the-factory parts appear smooth, but they actually have microscopically rough surfaces that need to rub against their counterparts and bed in, and that happens during those first miles of use. Once the components are polished smooth and broken in, friction is reduced, sealing is improved, and you’re ensured good power, fuel economy, and reliability. There are a lot of sliding and rotating parts within an engine, but what everyone gets riled up about when discussing engine break-in is the seal between the piston rings and cylinder walls. And rightfully so. Ring seal is the key condition that’s going to affect performance and longevity, so it’s worth thinking about.

How Should You Break In A New Motorcycle Engine?
What’s the best way to get a good seal on those piston rings? If you follow the break-in procedure outlined in your owner’s manual, it’ll recommend a 600, 1000, or even a 1500-mile process wherein you limit throttle and revs and constantly vary the engine speed. At the other end of the spectrum, there are people that say a gentle break-in is a waste of time and not an effective way seal the rings, and that a more condensed and aggressive break-in—some would say brutal—is the way to go.

How We Conducted Our Engine Break-In Test
To answer the question once and for all, in this MC Garage we assembled two identical Honda CB300F motors with fresh top-end parts, broke them in differently, and then compared the results.

The first engine was installed and run in gently as per the manual, which meant painstakingly limiting and varying the throttle and slowly ratcheting up the revs over the course of 1,000 miles. Then we swapped out the babied motor for engine number two. While engine one didn’t kiss redline until that final 1,000th mile, this second engine was given a minute to warm up and then taken right to the limiter and ridden at or near WOT on the highways of SoCal for the entire 1,000 miles. Both engines were initially filled with Bel-Ray semi-synthetic oil, and we changed the fluid and filter at 600 miles as recommended.

After breaking the engines in using drastically different methods, we performed compression and leak-down tests—which is a standard way of checking top-end health—then disassembled, measured, and inspected the internal parts. And the results, well, they might surprise you.

Engine Break-In Specs

Engine 1, “By The Book Break-In”
Installed at 1,828 miles, removed at 2,861 miles
Break-In Notes: Ridden gently. Didn’t exceed 50% throttle or 5,000 rpm for the first 600 miles, and didn’t exceed 75% throttle or 7,000 rpm until 1,000 miles. Didn’t experience WOT until 1,000 miles was accumulated. Ridden with constantly varying engine speed and load, no easy task on a slow bike in a busy, urban environment! Oil and filter changed at 600 miles.
Piston OD: 2.9910” at install, 2.9910” after 1,000 miles
Cylinder ID: 2.9925” at install, 2.9930” after 1,000 miles
Top Ring End Gap: 0.0130” at install, 0.0145” after 1,000 miles
Compression: 235 psi hot after 1,000 miles
Leak Down: 4% hot after 1,000 miles

Engine 2, “Brutal Break-In”
Installed at 2,861 miles, removed at 3,890 miles
Break-In Notes: Went to WOT within moments of first starting up, and was ridden hard for 1,000 miles. Did everything we’re told not to—lots of throttle and high-speed droning at steady throttle. Oil and filter changed at 600 miles.
Piston OD: 2.9910” at install, 2.9910” after 1,000 miles
Cylinder ID: 2.9925” at install, 2.9930” after 1,000 miles
Top Ring End Gap: 0.0130” at install, 0.0150” after 1,000 miles
Compression: 235 psi hot after 1,000 miles
Leak Down: 4% hot after 1,000 miles

[specialse]

After 20 plus years as a factory Honda motor cycle tech, at pre delivery inspection and road test, trust me, most new bikes have already seen the upper rev range before the customer gets it .

[PMitchell]

6:09 A third possible reason for long break-in recommendations is that if the manufacturer can convince you to ride gently early on, they are less likely to have to repair anything on warranty.

[DonnDIY]

Best of luck to you in the future. Sorry to see you leave.

[tomremeeus]

FINALLY someone who put this topic to the test. Thank you.

[bobz]

Wow ... sad for your leaving and injury. Get well and good luck!

[WhiteWhite]

Let me say this: I inherited a 2001 Yamaha Road Star 1600cc. Way beyond any bike I ever rode before. Because of its age, I had to do the maintenance myself and I didn't know how.
It was when you said you yourself had no formal training - just the maintenance manuals, pretty much - that gave me the courage to take a wrench to the bike.
I have it stripped down now, - I'm restoring it, going broke buying tools, but loving it. - thanks to you.
Best of luck. I wish you well.
-Paul

[You_tube_user]

Man you guys really went all out for this video. Major props, heal up my dude!

[cosmiccharlie]

Ari, one of your best moments on MC Garage was the tire changing video when you joked about throwing the take-off in the river. Good luck on the other coast.

[trekkydelirium-vroom]

you’re sill here 😎; but it’s your last video here 😢 you’re MC Garage; we will miss you forever. Thanks for all you’re awesome videos.

[rfrmobile]

As an old guy that loves riding I want to thank you for being here through the years for all of us on two wheels ! Good luck and come back as a guest when you can.

[joshconrad]

Get better soon bro, thanks for all of the knowledge you have given us.

[MichaelSabo]

In the beginning of this video, I thought to myself; "how can this be so controversial, why hasn't anyone compared methods side by side, " and then you did... Thank you 🤘😎

[patrickhd]

So much time, effort and expense went into this video - very impressive and a fitting way to go out on a high. The two best moto journos, bikes, cars whatever - just the best. Thanks for all the back-ins :-)

[liamollen]

Now this is dedication! It takes a crazy amount of time to do this video! Thank you:)

[buddywilson]

Sir, this was one of the best videos I have seen. I have always wondered about this process, and if the recommended break-in was just the factories wanting you to "take it easy" with the bike during the recommended break-in period. I want to thank you for all the hard work you put into this endeavor; and good luck on a quick healing from your unfortunate accident.

[JoaquinChea]

Ari, I’m gonna miss your excellent informative videos, best of luck in your new venture. Wishing you a speedy recovery from the injury.

[EonVendetta]

Thank you Ari for choosing to complete this video despite your accident. Best wishes and recovery, I hope you heal completely. Best of luck for your next projects. Big love

[theaquilaalba]

Get well soon Ari, what can I say, MC Garage won't be the same without you. Thank you for all your tips and the way you were translating it all to us. Hope to see you elsewhere with a lot thicker wallet - and soon. :) Ride safe mate. All the best.

[jasonsearle]

Sorry to hear about your accident! Good luck with your new ventures. Thanks for the uploads

[Thavisup]

We love you Ari, thank you for everything. 🙌🏼