Joined: Jul 2009
Location: Chandler, AZ
Modern engines are 99% broken in from the factory. Every new engine is run to redline and checked out before the bike is crated. Most of what is left of the break in, seating the rings, should happen in the first 20-30 miles, when it is important to build up a lot of pressure in the combustion chamber for short periods of time. I always break in new engines with many short bursts of full throttle, going all the way to top speed at full throttle by the time an engine has 30 miles on it. Main thing is to vary the throttle, and to not let it overheat. if the rings are not seated by the time you have 30 miles on the engine, they never will. The cylinder walls will glaze, and at that point all you can do to fix it is to rehone the cylinder and replace the rings, and break it in right. If you baby it when new, you will wind up with an engine that is down on power, and burns oil.
Even the owners manual does not specifically state that you cannot use full throttle when new, though it does imply that. Most owners manuals state to avoid PROLONGED use over a certain speed when new.
Once the rings are seated, the remaining break-in occurs over the next several heat/cool cycles. This is called "seasoning" the engine, and does not refer to using spices in it. New metal, like the piston and cylinder, are relatively weak compared to that of a used engine. They become much stronger as they are repeatedly heated and cooled. I remember reading about an experiment preformed by a race mechanic a long time ago. He took one new piston, and one used piston, and put them in an oven side by side, and heated them to a fairly high temperature for some time, then let them cool. He then measured the pistons, and found that the old pistons dimensions were almost the same as they were to start with, but the new piston was badly deformed. The same thing happens in a new engine, which is why it is important to not let the engine stay hot for long periods. Fortunately the piston is contained within the cylinder, which helps keep it from becoming deformed by the heat. As it ages with use, it becomes much stronger.
Though the manual usually says 600 miles, an engine is usually completely broken in by 100 miles. by the manual, the break in period on the '09 and older Honda Met was only 50 miles. On many 2 stroke mopeds it is 300 miles. On the genuine Stella 2 stroke, it is 1200 miles. Yes, you read that right. 1200 miles. But, the Stella does not have a modern engine, and worse, it is made in a third world country, where the metallurgy and build quality are poor. If this same engine were built out of the right metal, and built to better tolerances, it would be 10 times more reliable, and the break- in would be much shorter. It would also last longer. There is nothing wrong with the Stella's '60s design, IF it were properly manufactured. The Chinese use much more modern designs, yet their engines are even less reliable than the Stella's, for the same reason.
Now, while I would consider any modern properly made engine broken in by 100 miles, and able to be used normally, it will still loosen up over the next several hundred miles. The build tolerances take this into account, so it will wind up with proper tolerances after being used for several hundred miles, instead of being to loose, meaning worn out. Sometimes this means the vehicle will get faster over time, sometimes not. My Vino 125 still has the same top speed after 20,000 miles as it had after 200 miles. It has not actually required a valve adjustment in all those miles, though I did adjust them once, just out of boredom, and to get them perfect.
In modern properly built engines, use of synthetic oils from the very beginning should not be a problem. Many new cars come from the factory filled with synthetic oil. This does not apply to engines like the Stella, Royal Enfield, or anything Chinese.
As for Slick 50, it is still on the market. DO NOT use this stuff. It contains Teflon, which is a solid, and which can build up in and eventually plug oil passages, and destroy the engine. Dupont, which developed Teflon, does NOT recommend it's use in internal combustion engines.
IMO, in any small scooter, like the Vino 125 or Zuma 125 or PCX150, the oil should be changed every 1000 miles, regardless of what the manual says. This is due to 3 reasons. One, these small engines, even though not highly tuned, are put under a lot of stress by running them at full throttle most of the time. Two, they have a very small oil capacity, and oil functions not only as a lubricant, but as a coolant as well. Three, most of these engines have no real oil filter, which means the oil gets contaminated faster than it normally would.
I do not personally see any reason to use synthetic oil in these engines, unless you just want to, and can afford to. It won't hurt anything, but if changed every 1000 miles, won't do any good either. The only known benefit to synthetic oils is that they hold their viscosity longer than conventional oils, a moot point here. You still have the contamination problem to deal with, so you should still change it often. I would much rather have an engine full of clean conventional oil than dirty synthetic.
Synthetic is VERY expensive. It's cost is way out of proportion to what it costs to make it. It is sold for what the market will bear, and many people have been indoctrinated with the idea that it is bad to use anything else. Around here, a qt. of Mobil 1 motorcycle specific synthetic oil costs $13.99. You can buy a 5 qt. jug of Walmart Supertech oil for that. That's right, it costs FIVE TIMES as much as conventional oil. The SuperTech oil meets all new vehicle warranty requirements, even when it is used for the full time most new vehicle manuals recommend, which is way longer than I recommend. I change the oil in all my cars, and my larger liquid cooled motorcycles every 3 months or 3000 miles, whichever comes first. And when you compare new oil to oil which has been in an engine for 3 months/3000 miles, the used oil is always a LOT darker. Whether it is synthetic or conventional. My engines tend to last a LONG time, because I properly maintain them, not because I use super expensive oil in them. My Vino 125 still runs like new, after being run with SuperTech oil for 20,000 miles, changed every 3 months/1000 miles. And most of those miles were at WOT. Now if the tires would just last that long.
2002 Vulcan 750, 2013 Royal Enfield B5
2001 XT225, 2009 Genuine Stella
2012 Zuma 125, 1980 Puch moped