Busting The Engine Break In Myth | MC Garage

Published on Nov 12, 2018
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Motorcyclist Magazine
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.

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


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