The BREAK-IN Topic ... (for EJ) :P

[TechTMW]

There is some debate about the proper run-in of a motorcycle engine ... here's my take on it.

"Engine Run-In" is when the piston rings complete the machining process started at the factory. The cylinders are honed out with cutting stones, leaving Peaks and valleys - angular cuts on the cylinder wall called crosshatching. Crosshatching is good because it holds pockets of oil on the cylinder wall which assists in lubrication. The Object of Break-In period is to smooth out those jagged peaks - Just enough so that the peaks are flattened out a bit, but not so much that the grooves are completely worn out. The grooves must remain to hold oil for lubrication, and the flattened out peaks almost act as "bearings" for the piston ring to slide easily over.

That being said, the best way to do this is to vary engine speeds and loads. You do NOT want to "lug" the engine (Ride it in too high a gear for your speed) and you do NOT want to Redline the engine. Things like Full throttle hilclimbing and quickly opening and closing the throttle to moderate engine speeds are beneficial because they shorten break-in time.

why: When you Crack open a throttle, this increases the pressure on the piston and rings. This is good, because the added pressure allows the rings to properly seat. In addition, when you shut off the throttle after snapping it open, the increase in vacuum sucks more lubrication up into the pistion assy.

An engine not properly run-in will have glazed cylinder walls. this means that the peaks didn't flatten out, but due to excessive engine speeds, they rounded out or 'mushroomed' over the valleys, which is called Glazing. Glazing causes two problems, Blowby and Excessive oil consumption. Blowby is especially dangerous, because the combustion gasses (containing water vapor) are forced past the piston ring and into the crankcase. This water vapor combined with other combustion by-products over time turns into acids which etch the metal parts of your engine and increase wear. This is also why frequent oil changes are necessary if using cheap oil. Better synthetic oils (Such as Mobil 1) have acid neutralizers in them.

Finally, another reason for a proper break-in is that you aren't just breaking in the engine - you are breaking in the whole bike. This is especially important for the transmission, because this is the time when the hard machined edges of the gears will be gently worn down. Extreme loads on the transmission (Wheelies for ex.) will cause improper wear and may even cause gouging on the gears.

[emperorjordan]

are you talkin bout "BREAK IN"?

jest messin with you.