5

I don't understand the break-in periods needed for scooters/motorcycles. I know everyone says it, but I haven't found any explanation with some scientific backing to not making it an urban legend.

Point 1: Even more so, when we see that the 2 methods for break-in seem to be "Run it slow" or "Run it like you stole it" which are complete opposites and both apparently work.

Point 2: I don't see how the wearing of the parts will be any different if you have RPM's at 7,500 or 10,000 (apart for maybe overheating due to the friction). It's like the difference of cutting wood with a saw or an electric saw. The electric one goes faster but the result is the same. You want a lot of friction to cut through.

Can any one actually back up the need of a break-in period?

  • 1
    Here's a response to a break in question. mechanics.stackexchange.com/questions/15596/… Here's the thing. Changing the old frequently, you will find flakes and the oil will get metallic looking quickly, change it, get it into the sun, you will see a snowstorm of minuscule metallic particles glistening. There is physical evidence of intensive initial wear. The procedure, well....probably subjective too. One thing I do believe. Change your oil a lot. – DucatiKiller Jun 3 '15 at 7:33
  • Yeah changing oil for sure. I'm just wondering on what different wear-in effects are depending on the RPM. Seems strange to me (I'm no mechanic, so no idea). – denislexic Jun 3 '15 at 14:29
3

Instead of recreating the wheel, here are some pretty good reasons why you need to do a break-in on any engine, be it a motorcycle or a car. I found it on this page. I don't necessarily agree with everything the person says on the page, so I'll leave the rest of the reading up to you.

The What:

Every new engine has internal components that must be "worn-in". This "wearing-in" of components is what's known as "break-in". The main components that need to be broken-in/worn-in are the valves, the cylinder bore, and the piston rings. These components must be worn-in so that they mate properly with the surfaces they will interact with over the life of the engine.

NOTE: At this point on the page the author states about valves not sealing correctly if not broke-in right. I will differ with him somewhat here as the way you get the valves to seal is to properly lap them prior to putting the head back on the engine. If lapping isn't done correctly, the valve will never seal and you'll lose all kinds of cylinder pressure while running the engine ... this is so for a car engine, I'm assuming it is exactly the same for a motorcycle.

The Cylinder Bore and Piston Rings -

The cylinder bore of a new engine is somewhat rough, and the piston rings are not properly mated to the cylinder bore. Some of the cylinder bore roughness must be worn down and smoothed out in order to create just the right amount of seal between the bore and the piston rings. Also the rings must be worn in correctly to mate with the cylinder bores. This process must happen properly in order to create the right kind of seal that will keep the combustion gases separated from the engine oil, and vice versa. Furthermore, if this wearing-in process does not happen correctly, the cylinder bore walls can glaze over, which will cause a lack of lubrication between the cylinder bore and piston rings, leading to overheating, a loss of performance, premature wear, and a loss of reliability. If this glazing does occur, the only way this problem can be corrected is for the engine to be torn down, the cylinder bores re-honed, and new piston rings installed, after which they must of course be broken in correctly, or it must be done all over again until it is. So you see how crucial proper break-in of these components actually is.

The Why:

Quite simply, these engine components must be properly "worn-in" to ensure good performance, reliability, and longevity; it's really just that simple. If these parts are not worn-in correctly there will be a loss of performance in every way. There will be a loss of power, poor fuel efficiency, increased oil consumption (burning oil), among other problems.

I'd also like to point out, in flat tappet engines, you need to vary the engine speed at 1500-2000 rpm for about 20 or you will flatten cam lobes out. You do this so the cam lobes and the base of the lifters will get a sympathetic wear pattern to them. If you let your engine idle upon first startup, you will wear through the hard metal surface of the cam lobe and lifter face and you will wipe out your cam. Roller cam engines do not have this same problem.

There is a huge amount of controversy over the how do you break in an engine out there. There are two trains of thought on this: 1) break it in as the manufacturer recommends so as to maintain warranty; 2) run it like you stole it. I don't completely agree with the stole it method, but believe the better way to do it is hard rather than soft.

By far the best method I've seen is this one. Not only has the guy documented exactly what he does, but exactly why he does it (with pictures to show you the difference). Basically, he is saying do the following:

Do Three 1/2 Throttle dyno runs from 
40% - 60% of your engine's max rpm
Let it Cool Down For About 15 Minutes

Do Three 3/4 Throttle dyno runs from 
40% - 80% of your engine's max rpm 
Let it Cool Down For About 15 Minutes

Do Three Full Throttle dyno runs from 
30% - 100% of your engine's max rpm
Let it Cool Down For About 15 Minutes

You'll notice he's talking about doing the runs on a dyno. You can do this on the street as well, but it works better in a controlled environment like a dyno, or a race track, or wide open country roads. A couple of the key things you want to remember is not to lug the engine and let the engine decelerate on its own (creating a large amount of vacuum in the cylinder). If done on the street, you can vary what gear your running in to complete the above sequence. On the dyno, you need to be running it in a higher gear because you don't have the load that you do on the engine from wind forces.

One of the key things which is stated on the page is that with the proper break-in, it can be worth 2-10% more power out of the engine. It will also help for the longevity of the engine. Yes, the engine will run, but it won't run as good as it could have, won't last as long as it could have, and you'll usually end up burning oil and having blow-by a lot earlier than would otherwise be expected.

If you choose to use this method for break-in, please read the page in its entirety. There is a lot of good information on there.

-3

I bought a new. Gy6 150 c.c.I broke it in with break in oil from maxima oils.I drained the factory oil.I started it and let it warm up a little bit.may be 3 minutes.during that time I rolled the accelerator up and down,up to a little over 2000 rpm's .I would say,up to 2200'..2300 rpm when warmer,like after the first minute from starting it,but rolling it up and down,gradually.with no stress on the motor.Then I rode it for a mile non stop and I would gradually take it up to 30 m/h and completely release the accelerator .The idea is to feel your putting pressure on the cylinder walls by. Gradually increasing the speed till you reach 30 miles/an hour and release it...Idleing a new engine at a traffic light for example increases the Temperature in the motor.I do it at night.These are the miles increments and cooling intervals I have tried with success like I never had in my previous 28 Cycles.Yes.I have owned a total of 28 motorcycles and big scooters and all sizes combined.What kills a new motor is the heat.so riding for a few miles and letting it cool off is very wise.Proven fact.No myth.the key is to open the throttle steadily and gradually.Tune yourself with the engine and feel how you sit those rings as if you were sanding them against the cylinder walls...First 7 miles...30 m/ h Next 7 miles...up to 35 m/h...and so on up to 50..Always with a 5 m/h. Increment every 7 miles.I live in hot Florida.The heat might not apply to everyone.which is a cool thing.After that period drain the oil while is still warm.Not hot.Put Break in oil again.and your scooter is almost ready.do not travel far non stop.give that motor a break and let it cool off.and then ride it again.vary your speed wisely.its better to stop it and turn it off when during the first hundred miles.you will feel the smoothness as it break in.and you will feel its ready to ride it far.Let it cool off until you can bear the heat on the valve cover.or let it cool off completely.Drain that oil as soon as it gets darker than when new.I would say 300 miles and from there on.put mineral oil 10w 30 and change the oil when it gets darker.it depends on how you ride...I love synthetic oil.I use it as soon as I feel my motor is ready.usually after a thousand miles...At all times make sure your scooter does not over heat.Use 93 octane from Mobil during the first 1500 miles.You can use 87 after that.but make sure you use an additive.I have used Lucas for years successfully and its hot where I live.Hot like an oven.I use 3 ounces in 10 gallons and feel the difference it makes.Gases nowadays contain a 3 times as much alcohol than 10%.Half the additives than years ago.these additives add lubricity to the gas.You want your scooter to run on lubricated gas.The top ring needs that lubrication in the gas to counteract the oxidizing effects of water in the alcohol.This is what has worked for me.My engine has 15734 miles now..It runs better than when new.I use a pcv valve hooked to the valve cover and a crankcase ventilator to release the pressure inside the motor.This is awesome,never a blown up seal issue even when using cheap synthetic oil.Learn about Api services of the new oils,most are SN......SE or SF..ideal...I add a little bit of Lucas or Stp oil treatment.Not much.I try adding a little to get the right thickness required by each particular engine and season.I don't do it when it's not so hot.I only add these as I feel its time to use a thicker oil.I usually use 10 w 30.So I can thicken the oletsil as needed.every case is different.Add ,lets say ,10ml to your oil if needed and run it.if it runs good leave it right there.if not add 10 ml more,till you feel comfortable.Too thick Won't help.Use your common sense.I hope this helps.Thanks..Something I forgot,I use a hill up and down during the break in period.its a hundred feet long heel,11 feet high..that helps put pressure on the rings.but only a few times..and then let it cool off.and you can repeat it.it seals perfect.No spark plug replacement yet.no cleaning.literally maintenance free

  • 1
    Could you please edit this to add some paragraph breaks? As it is it's virtually unreadable, and as such isn't very helpful... – Nick C Aug 6 '18 at 9:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.