Accelerating, changing gears
You can shift anywhere from 6 to 13k, depending on how fast you're going (accelerating). If you're poking along behind a grocery-getter from a stop light, a shift point of 6k makes sense. If you're accelerating normally and want a good compromise between performance and fuel efficiency, shift around 8-10k. If you're trying to quiet the rowdy kids next to you in daddy's 318i, cook it up to 12k before hitting the next gear. Cruising revs should be between 6-10k.
Shown here are torque (L) and horsepower (R) charts from Motorcycle.com's
As you can see, power starts taking a major hit after 12,250 rpm. There's no use pushing it past that. Shift up and take advantage of the power in the next gear.
On the other end of the spectrum, you don't want to run your engine too slow, either. "Lugging" (or "bogging") the engine is not really good for it, and won't leave you in the proper gear should you need to get out of a situation fast. Any time the engine speed is being determined by load (i.e. going uphill, in too high a gear, etc.) rather than by the throttle, you are lugging. If you twist the grip and little or nothing happens, then you need to downshift at least one gear.
There are two kinds of downshifting: downshifting to slow down, and downshifting to speed up.
When slowing down, you should ride your current gear to about 4k, then quickly kick it down as you pull in the clutch and blip the throttle; this will bring the revs back up to about 4500, which you can again ride down a bit before going down to a lower gear. Using this method, you can stop more quickly, and will not encounter a jolt. However, try to use the brakes (instead of the engine) for the majority of your slowing force.
When you slow down from 60 mph, kick down a gear every few seconds. It is recommended that you always stay in "escape gear"; keep your eyes on the mirrors for forgetful people behind you, as well as those in front and to the side. Be in the proper gear so that you can accelerate away from any approaching danger. Along the same lines, stay in first gear while stopped at a light.
When accelerating, you can pretty much downshift whenever you want a power boost. However, downshifting when doing anything over 11k rpm is pretty pointless, as you're already in your powerband. You want to try to downshift to keep revs between 9 and 12k; this is where you get the most tug for each twist of the wrist. You should let off the throttle momentarily while quickly disengaging the clutch and kicking it down, then opening the throttle up wide to match engine speed as you release the clutch lever again; this will give you the power you need to accelerate effectively.
The EX250 engine, along with those on most 'sporty' bikes, was designed for high-rpm use. There seem to be some compromises which make it harder to use at engine speeds lower than about 6000 rpm. Basically, there's no reason to ride any lower than 5000 rpm, except for while sitting at a light. Even then, you can't depend upon the engine for any power that far down.
The following suggestions are just that. Get used to what works for you, and keep in mind that your Ninja likes to work at high engine speeds. These are not guidelines for how to get the best gas mileage from your engine. However, they will help you avoid stumbling at low rpm and keep the engine spinning fast enough to be of some use if you need to suddenly go faster.
Clutchless shifting can easily be done on a motorcycle: it's just a matter of matching the rpms. On upshifts it's just a matter of backing off the throttle for an instant as you bang the box into the next gear. On downshifts you have to rev the engine up a bit as you drop a gear. Of course, the clutch is there for a reason, and shifting without it will wear your tranny out more quickly. In short, the only place this technique really has a place is on the racetrack, where tiny fractions of a second can make the difference between first and second place.
Some advice? Learn how to do it and then don't, unless some large person named "Mad Dog Al" is chasing you with a chainsaw.
Shifting when stopped
It's completely normal to have trouble getting the bike into first from a higher gear when stopped; from time to time it can happen to any rider.
One thing you can do is this: When stopped in a gear higher than first, press down on the shift lever; if the bike goes into the next lower gear, fine. If not, slowly let out the clutch while pressing down on the shift lever. The bike will then go into the next lower gear just as the clutch engages -- do not let it all the way out or you'll kill the engine. Repeat as necessary till you get to first. Rocking the bike back and forth also works, but this method takes less effort and is probably faster.
Note that it's easier and safer to shift down as you slow down (while the bike is still rolling), rather than waiting until you're stopped.
You have to be moving to shift
The EX250 has the Kawasaki positive neutral finder. This means the bike is set up to keep you from shifting past neutral at a stoplight and looking stupidly at your left foot while you go back and forth between 1st and 2nd. This is usually a good feature, but you have to remember a few things about it.
In order to shift past neutral the rear wheel has to be turning. This usually means that the bike is moving. The rear wheel has to be turning and you also must be in first gear. You can't just turn the rear wheel in neutral and shift up; you must go down into first and then shift.
You can shift through the gears on the centerstand with the bike running, but this is not recommended. If the centerstand gives way you could end up chasing the bike several hundred meters up the road or digging it out of the end of your garage.
Avoiding missed shifts or false neutrals
If you have trouble with shifting and finding the bike isn't in gear (particularly on upshifts), you're hitting false neutrals. This is where the transmission doesn't shift completely between gears. The problem is typically caused by transmission components hitting the 1-in-100 condition where the dog can't engage with a gear. It can also be caused by not putting enough pressure on the gearchange lever, but this is uncommon.
To avoid this problem, use the following procedure when shifting:
When you let the clutch out, the pressure on the gearchange lever will cause the transmission to slip into gear if it wasn't already. If you get into this habit, you'll never hit a false neutral again.
Make sure to avoid the common fault of failing to allow the shift lever to fall all the way to the bottom between up-shifts. This will cause the bike to miss shifts.