The dilemma of 'Engine Break-in'
Running in a brand new engine
Bringing home a brand-spanking new motorcycle is an experience second to none for most bikers. However, the real labor of love begins right from the minute one begins putting down kilometers on that shiny new ODO meter. So what can be the first step after bringing your bike home and what does the phrase “running-in” entail? Here it is:
Considered to be the most essential time in any engine’s life, running in should be followed religiously in order to ensure the engine lasts long and keeps you company on those long interstate rides or short blasts up the hills. In the bygone era of the 70s and 80s, manufacturing technology was not as advanced as it is now. This usually led to very relaxed tolerances in engines leading to various high spots on the metal surfaces and required a proper 1,000 km run-in period for all the surfaces to mate properly (e.g. mating of the piston rings with the cylinder walls). However, the industry has come a long way from those days, with considerable advances made in metallurgical and thermodynamic technologies as well as with machining and casting.
This means that a brand new engine is theoretically ready to go full power out of the box. However, the key word here is “theoretically”. Despite having super close tolerances, the engine components still require some time to seat properly. Hence, a new engine should always be warmed up before riding so that it has adequate oil circulation and is close to its optimum operating temperature. Take it slow and easy on your first ride. Small throttle openings and smooth shifts at the correct RPM will go a long way in keeping the engine happy and performing at its best level for decades.
It is advisable to use good quality mineral engine oils for the running in period as this type of oil provides a good amount of friction for the engine components like the piston rings, the crankshaft bearings, the camshaft etc. to seat properly with contact surfaces. However, rest assured that using semi-synthetic or full synthetic oil will not damage the engine. Changing the engine oil and oil filter after the first 100kms, then at 500km and again at 1,000kms will also go a long way in keeping the innards of your bike’s engine happy because this can clear out any possible debris left out during the manufacturing process. Again, it is not absolutely imperative to do so.
When performing running-in, be sure to first warm up the engine by letting it idle for a minute or so (this is a good practice even when the engine in properly
broken-in). This allows the engine oil, which is all drained into the oil sump when the bike is parked, to circulate all through the engine. Then start off by using small throttle inputs when riding for the first 5-6 kms. Keep the bike in the right gear that will provide the optimum torque and drive. Slowly proceed through the permitted rev range and shift gears smoothly. The “Owner’s Manual” is the best place to find out what is the RPM or speed limit in each gear for a certain motorcycle. What this does is that it gives the engine a chance to experience varied loads at different RPMs and in different gears. When slowing down, do not pull in the clutch and coast to a stop. Instead, blip and down-shift and let the engine braking help you slow the bike. Simultaneously apply the brakes as well because they also need to be bed-in.
When running in a brand new bike, be sure to vary your RPMs. Do not ride at one fixed RPM. The variation gives the engine a chance to experience different loads and heat levels. Once past the 500 km mark on the ODO meter, one can progressively begin opening up the engine. This does not mean whacking the throttle open every chance you get. No! It means that one can rev the bike to about 60% to 75% of the available rev range without over-stressing the engine. Be sure to do this in a progressive and smooth manner. Once you approach the 1,000 km mark, you can finally open her up to enjoy the upper range of the bike’s rev band. But be sure not to red-line the engine a lot. The engine still requires some love and affection before it is ready to take on the abuse of a lifetime.
There are many controversial methodologies out there regarding how to run-in a new engine. One such method is the “Moto-Man” method to run in the engine hard right from day one. It is a point of personal choice whether to do an “easy” or “hard” run-in. The results will eventually depend on the way it is done.
What PTR recommends: There is a common and yet erroneous notion that the best engine break-in is achieved by treating the bike with utmost care..The manufacturers add to that belief by asking the user to keep the bike below xyzv rpms untill abcd kms. While we at PTR aren't recommending throwing the manual out the window we certainly urge every biker to have a deeper and a better understanding of what engine break-in really is. So heres whats happening when an engine is operating.
A force known as Break Mean Effective Pressure or B.M.E.P is generated within the combustion chamber of an engine and is produced by the burning of the fuel and air mixture in the engine. The higher the throttle the engine is running at, the higher the B.M.E.P. is and conversely as the throttle is reduced the B.M.E.P. becomes less. Now whether you want it or not B.M.E.P. is an important part of breaking in an engine. The surface temperature due to the friction between the piston ring and the inside wall of the cylinder depends on how high the B.M.E.P. of the engine is. This is clearly because under heavy throttle with more B.M.E.P. you are pushing the piston rings harder against that cylinder walls. Now with more friction comes more heat. And this heat helps in seating the piston rings well onto the cylinder walls. Allowing too much heat to build up will make the structure of the lubricating oil molecules to break up creating an unwanted glaze on the surface of the the cylinders walls. Glazing prevents any further seating of the piston walls. What do we do then ? Should we apply too little B.M.E.P. aka little throttle pressure ? To begin with it looks to be the safest bet untill we look deeper and realise that less throttle also results in glazing of the surface walls. Whether the pressure is less or more once glazing occurs your engine cannot break-in well anymore. The use of low throttle does not expand the piston rings enough, and a film of oil is left on the cylinder walls. The high temperatures in the combustion chamber will then oxidize this oil film so that it creates glazing of the cylinder walls just like what happened when the lubricant molecules broke down due to too much throttle. When this happens, the ring break-in process stops, and excessive oil consumption frequently occurs. Infact one of the ways of telling if the engine has been properly broken in on a second hand bike is to look out for its oil consumption.
Like in everything else in life we must strive to toe the middle line. Too much throttle as well as too little throttle, both manage to interfere with the engine break-in process. So how much throttle should it be ? No matter what you do you should never lug the engine in low gears. That does more damage than revving an engine. Vary your rpms all the time and avoid shifting into the top gear. Constant load on the engine is again very detrimental to the engine. Keep varying the throttle openings to vary the rpms and the load. Never use a synthetic oil until about 1000 to 1500 kms. Use of synthetic oil during the break-in phase is guaranteed to glaze the surface walls of the cylinder. Much can be read about engine break-in on the web so please do take your pick. Happy Miles!
Wednesday, 25 April 2012 07:18
Useful info for new bikers. This article ties in with what i've followed thus far. I don't baby the throttle nor do I rev hard. Just ride normally, the way you would if you were commuting without a hurry. Thank PTR!