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Wednesday, January 26, 2011

Motorcycle Engine Break In

Engine Break In or Engine Run In, what ever you call it, is probably the most discussed and controversial motorcycling topic discussed over Internet and amongst bikers. This is the single most important procedure in the entire life cycle of an engine or should I say, the Piston/Cylinder block which defines, how your rides gonna be in the long run.

The million dollar question here is, why do we need to break the engine after all? Well, simply put, even though the concept is termed as engine break in, we are actually building the engine as we are using it. Let me explain how.

The first few hundred kilometers of your new bike/engine decides how well it would keep on performing for the rest of it's life. The basic purpose of engine breaking is to seat the compression rings against the cylinder wall. Here it's strictly the physical mating of the compression rings against cylinder wall, i.e. we are talking about rubbing a bit over sized piston ring getting rubbed against the cylinder wall and setting down to a perfect fit/seal with the cylinder wall. Once a perfect sealing of the piston rings has been achieved, they won't allow combustion gases - blow by gases, to go past the rings and get accumulated in the crank case section of the engine. This in turn helps the crank case section to remain clean and cooler during operations. If the blow by gases are allowed to accumulate in the crank case, it will heat up the crank case resulting in the crank case getting pressurized and contaminated with combustion gases, which would in turn force the normal oil vapors out of the engines breather and hence the engine would be consuming more oil.

Apart from controlling the blow by gases, the other major function of a good sealing of the piston rings is to control the amount of oil on the cylinder wall for lubrication. If the sealing is not good, this would allow more oil than required to get accumulated on the cylinder wall, which would burn during the combustion cycle producing unwanted combustion gases.

So, automatically the question comes to mind as to how this sealing is done? It's fairly simple, to create a sealing by rubbing action, we need to create to create friction and to create friction we need a coarse surface. That coarse surface is created by honing the cylinder surface which would be in contact with the piston rings in a crossed hatched fashion.

The peaks of the cross hatched surface rub against the piston ring surface to seat them down and the valleys act as oil reservoirs to provide lubrication to the process. The more the Break Mean Effective Pressure - BEMP (which is the force produced from the controlled combustion of Air/Fuel mixture acting on the Piston Head), the more vigorous rubbing occurs between the cross hatch peaks and the piston ring surface. The whole idea of a proper break in is to delay the glazing of the surface of the cylinder as a result of this friction so that the piston rings get ample time to seat in.

So, how do we break in to get that proper piston sealing? That's probably the most controversial question in biking forums. Here's what I did for my Pulsar 200 and I'm sure I'm gonna sound quite crazy with it.

For me, the break in period lasts upto 2500 to 3000 km. During this period, there are four things which should be kept in mind -

1) The type of engine oil that is used. Using a high load engine oil is suggested during this period and fully synthetic ones should be strictly avoided. Fully synthetic oil would only help in quick glazing of the cylinder wall beating the whole purpose of break in.

2) Divide your rpm range as per kilometers traveled. Like for the first 500 km, I did not cross 4000 rpm range, then for the next 500 km I did not cross 6000 rpm range during continued usage. Try to be below the top gear during this initial 1000 km.

3) Keep varying the load in short bursts of 10-20 seconds. DO NOT keep riding at the same rpm range for continued periods. Once the bike crosses 500 km it would be good to red line the bike past second gear, but make sure that the engine does not heat up, so we would be doing that in very short bursts, might be less than 10 seconds.

4) Plan your rides accordingly so that the engine cools off to ambient temperatures between Stop and Start of the engine. This is very very important, else the engine would not get time to cool down and would keep on heating, resulting oxidizing the oil film on the cylinder wall and eventually glazing the cylinder wall.

Once the first 1000 km on the bike is done, the initial results of break in should start showing up. The bike should be eager to revved up, but still we need to control the right wrist for the remaining of the period. After the initial 1000 km, now we are free to engage the top and try red lining, but again for short bursts.

In no case during the entire engine break in period, we should allow the engine to heat up excessively.

It's only after the first 3000km that we can see the full benefits of a good engine break in. The motorcycle should be very rev happy at all gears and that include the first gear too, should easily red line without much fuss and should feel as smooth as new and above all, optimum usage of oil.

Finally, to end this discussion, always be in consultation with a good friend/mechanic in regards to the break in procedure of your individual motorcycle, as a good advice is very rare and comes handy when ever you get it, where ever you get it and from who ever you get it.
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  1. Hi bro,
    Nice technique with engine.
    :-) :-)
    I thought this is bad for new bikes as it would hamper the performance.
    :-) :-)
    Though i was suggested by my friends for my bike,but i didnt tried it.
    :-) :-)
    Now my bike has crossed 4500 Km.
    But surely i will do it in my future bikes..

    Thank you,

  2. Saurabh,
    Which bike do you have? And yeah, at first look this technique might look a bit harsh because by default we think that on a new bike we need to take it easy, but when engine break in comes to picture, the "take it easy" part becomes more stepped rather than literally.

  3. I have Discover 135 'O' ring chain.
    The one in my profile pic.
    Will upgrade to my new bike in a couple of months.
    :-) :-)

  4. The Disco 135 is also a sweet ride :) Almost close the Pulsars ver 1.0 ;)

  5. Good write up Sajal bro,

    actually I was thinking of writing a similar post on my blog.. great minds think alike :-)

  6. Payeng Dude
    Thanks Bro :) I'm not sure if I've a great mind, but definitely I try to think like you :)


Item Reviewed: Motorcycle Engine Break In Description: Rating: 5 Reviewed By: Sajal
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