How do I check my oil?
As you've probably figured out by now, the oil system on your 250 is slightly different from what you may be used to on a car. The biggest difference for those new to motorcycles is the sight glass instead of a dipstick. Another difference is that you really do have to check your Ninja's oil more often than most modern cars.
Sight glass location (L); Sight glass markings (R):
There is, as is always the case when it comes to oil, some disagreement as to when to check it. Conventional wisdom from the old-timers on the board has been to check when the bike is warmed up, after waiting five minutes after shutdown for the oil to drip back to the bottom of the engine. The owner's manual says to do it as part of your daily safety checks, which would imply looking at the sight glass before you start it up. We at FAQ say: Do both. Checking your engine oil often can only be good for your bike and, as there are only 1.9 litres (2 quarts) in the crankcase, losing even a little bit can be significant.
So, check your oil at the end of your ride, after the bike has sat for a few minutes. The next time you go out, look at your oil level before you ride, assuring yourself that there is some oil in there. Then after your ride, wait a couple minutes and look again. This could be after you shut it off at a gas station, or after you've de-geared and stretched a bit when you've gotten home from a ride.
Here's how the owners' manual says you should check it: "Check the engine oil level through the oil level gauge. With the motorcycle held level the oil should come up between upper and lower level lines next to the gauge."
This translates as: "Full" is the top line (near the top of the window) when the bike is held vertical and both wheels are on the ground. Keeping the oil at or close to the upper mark is desirable, but do not overfill it, as you could blow a gasket. Only add a small amount at a time.
Note: When the bike is on its centerstand the level in the sight glass will be lower. When both wheels are on the ground the level will show a more full reading. (The bike is tilted forward and isn't level when on the centerstand, so the level appears a little lower.) The recommended check method is with both wheels on the ground, but there's only a small variation between on and off the centerstand; as long as you're in the middle of the sight glass or above with either method you're fine. Be happy and go ride.
Why it is very important to check your oil frequently
What does this mean?
Your bike may consume oil while riding. If riding at high speeds, oil may need to be added as frequently as every tank of fuel.
It's certainly good to check your oil before starting the bike up, but if riding for more than a tank of fuel, you must also check the oil when you're on the road. Add oil if it is below halfway down.
If you ride consistently at high rpm you may want to change your gearing to lower the rpm that the bike travels at.