Break-in / Run-in


The grain of truth here is that if the piston rings are never seated against the cylinder walls by proper break-in, they won't seal and the engine will never develop full power. On the other hand, how fast should break-in be? Do you take out your new, zero-miles bike up the interstate? No, a normal break-in would be as described in the maker's manual, and performed with understanding. This is all that is really  needed.

No matter how fine the surfaces produced in manufacturing on cylinder walls and crankpins, they are like the Alps in comparison with the much finer profiles that proper break-in will create. Break-in is the final machining operation. The oil films that will support moving parts in operation may be as thin as 1.5 microns (.00006 inch), so to avoid piercing these' films, the Alps of manufacturing must be scrubbed down to even lower height by the process we call break-in.

A normal break-in calls for a period (usually 500 to 1000 miles) of controlled operation in which the engine is never steadily, heavily loaded. You would not, for example, climb long hills on full throttle and low rpm. The idea of break-in is to impose short periods of various loads, separated by recovery periods. While the Alps are at work, knocking each other down, wear particles and heat are produced. The recovery periods allow the heat to dissipate, and allow the particles to flush out from between surfaces and be swept away to the bottom. Once break-in is complete, engine oil should be changed after a thorough flushing of the crank case with about half liter of new oil. Once this is done break-in is complete.

But remember, your bike isn't immediately transformed into a racing machine after the break-in. Once the break-in is complete, start subjecting the engine to gradually increasing loads before you finally touch the peak.

One more important aspect to be considered here is, how much oil should you use during break-in? It would be a good idea to use a little more oils than you normally would on an engine which has been fully broken-in. However, take care not to over add oil, appropriately about 5 ml extra per liter should be fine.


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