Safe Engine Break-In - HB Tech

OK, so you just bought yourself a brand-new motorcycle or complete new engine, or you just finished assembling that monster motor in your garage. Human nature being what it is, it's very tempting to immediately start up your new hot rod and rev it a few times before roaring down the street to impress the neighbors. But if you haven't followed the recommended engine break-in procedures, you are making a huge mistake.

The purpose for breaking in an engine is to allow components to gently wear against each other and to form proper final running fitment. Piston rings need to seat properly to the cylinder walls to maximize cylinder pressure and optimize power. An improper break-in can score the cylinder walls instead of allowing the rings to slowly conform to the wall surface. Valvetrain components and bearings also need a certain amount of gentle wear for proper mating to protect against galling. However, the wearing of parts introduces metal contamination into the engine's oil supply. As such, frequent oil and filter changes are necessary during the break-in period to protect against excessive component wear and permanent damage to vital engine parts. Correct engine break-in procedures are important and prevent unnecessary component damage while ensuring long engine life, minimal oil consumption, and maximum power. Engine break-in is divided into four major phases: prestart, initial start-up, run-in, and follow-up.

Prestart requirements include cleaning the oil tank, oil cooler (highly recommended), and oil lines, priming the engine's oiling system, checking oil pressure, and verifying the correct ignition and carburetor or EFI settings. Never run an engine without an oil filter, so check that one is installed.

Initial start-up is important in the break-in process and includes verifying oil pressure, heat-cycling the engine several times, checking for oil and gasoline leaks, listening for abnormal engine sounds, and maintaining the proper oil level in the tank.

Run-in is the actual time the motorcycle and engine are run on the street (or the engine is run on a dyno or break-in stand) to put either street miles or run time on the engine so parts can gently break in and conform to final fitment clearances. This phase includes several oil and filter changes to flush the engine's oiling system of contaminants generated through the normal wear and mating of parts. As during initial start-up, checks should be made for oil and gasoline leaks, abnormal engine sounds (including detonation-ping, knock), loose or malfunctioning parts, and proper oil level in the tank.

Follow-up procedures entail rechecking the torque of all accessible engine and chassis fasteners with the exception of the cylinder head bolts. Head bolts are normally not retorqued. Some manufacturers recommend retorquing fasteners at every oil change. Additionally, adjustments to the induction and ignition systems are commonly made at this time to optimize the engine's tune, and the engine's oil and filter are changed.

The number of break-in phases you're responsible for will depend on whether you bought a new motorcycle, a complete or unassembled engine, or whether you built your own engine. For example, if you bought a new motorcycle, prestart and initial start-up functions are performed by the manufacturer, and you would begin break-in procedures by following the manufacturer's run-in and follow-up procedures. If you purchased a complete assembled engine, you must verify what, if any, break-in procedures were performed by the manufacturer. Some complete new engines are not prerun by the manufacturer. If you had an engine rebuilt by a professional mechanic, the mechanic should have performed prestart and initial start-up procedures. However, there could be exceptions, so you must verify what phases of break-in, if any, have been completed. Be careful not to make any assumptions. On the other hand, if you built the engine, obviously, you are responsible for all four phases of break-in.