Do I really have to follow this break-in period?
What is break-in anyway?
It is the procedure that helps "seat" moving parts in the engine, by wearing in metal to metal contact surfaces. The main purpose of the break-in is to seat the piston rings to the cylinder walls. These parts must be physically worn into each other to achieve the best possible seal to prevent blow-by (hot gases escaping thepast the into the ).
What is the best way to break an engine in?
There is no "right", or "best" way to break in an engine. This is a much debated topic, with many different methods existing. Several are listed below; pick the one that sounds best to you.
General Break-in recommendations
The fact is that an engine is not fully broken in for several thousands of miles. During that period, you have to respect it more than you would a fully broken in engine. That said, the Ninja 250 is probably 95% broken in by 500 miles. And it's probably 90% broken in by 50 miles. Still -- and this is really beside the point of this article -- the engine is not fully broken in until 15-20k miles or so, when everything in the engine is completely seated, at which point the engine begins to ever-so-slowly deteriorate (just like you grow until you're 27 years old, then you start to die).
Now, what does "respecting the engine" mean? Generally, it's all about friction and lubrication. Until the engine is run in, there is more friction and less lubrication on critical parts (, , , , etc). These parts must be in good shape for the engine to run efficiently and for long periods of time. Keep the rpm at the maximum for too long and the unworn components will get too hot. What is "too long"? What is the proper "respect"? What are the proper rpm? This is a matter of much disagreement, but here is what is usually agreed upon:
Note: Unlike some more modern machinery, the EX250 doesn't have any special oil for break-in from the factory. Feel free to change your oil as often as you like.
Kawasaki simply recommends observing a 4,000 RPM limit for the first 500 miles. A lot of people follow this break-in recommendation and enjoy reliable, long-lasting engines. However, it has been pointed out that every motorcycle model Kawasaki makes comes with the same 4000 RPM initial break-in limit sticker on the, and they have been doing this since at least 1982. Here are pictures of the break-in sticker from a 26 year-old KZ440 (it's really not illegal to remove these):
Because of gearing, this one-break-in-fits-all system isn't really fair to the EX250. Some bikes do 90 mph or more in top gear at 4000 rpm, while the Ninja 250 only does 35 mph, so the bike that does 90 in top gear will consume 500 miles sooner. It's really backwards, because the EX250 works harder and would break itself in sooner than, say, a 2-liter, 5000-rpm-redline Kawasaki Vulcan.
Is there a formula for all this? Not exactly, but here's a good method I would use. Make the engine work harder the more you break it in, always keeping the temperature and friction inside in mind. This motor was basically brand new, then rebuilt from scratch with minor oil flow and valve seat modifications. It completed 9500 miles during the Iron Butt Rally in Aug/Sept 2005. The motor was started for the first time in March 2005. As of January 2006 it had 22,000 miles.
NOTE: Complete cooldown between each run (at least 4 hours).
At this point the bike went on the 48-hour MD-20/20 Rally, covering just over 2000 miles during the 48 hours. In July it went 5100 miles in 4 days, 22 hours. It had 10,000 miles on it at the beginning of the IBR in late August. Changed to Rotella 5W-40 Synthetic at 5000 miles, just before the 5-day ride. I felt the motor began to feel 'broken-in' between 7-9000 miles.
This is the strongest Ninja250 I've personally ridden. The amount of oil it burned during the IBR varied from none to about 1/4 qt. per 1,000 miles.
Duke's break-in method was based on this article.
MotoMan (Note how it is similar to Duke's)
Here's a link to another board member's account, who used a similar method: Yeager's EX250 Maintenance Log.