EX250F key blanks
There are a lot of key choices shown below, but the best thing for you to do if you need a new key made is to visit your local locksmith (not Joe Teenager at Home Behemoth – a real locksmith) and have s/he duplicate the one you have. A good locksmith should be able to tell which blank needs to be used, but some of them may not do much motorcycle business. This page is to help you help them.
For a complete dissertation on the relationship between you and your vehicle keys, go to What do I need to know about keys?.
Here is what some of the blanks discussed here look like:
If you're going to order key blanks online because you can't find them locally, you should probably go with Kawasaki part number 27008-1173 or Silca KW12BP. Either of these will fit EX250s made from 1988-2007 without modification.
OEM Kawasaki key blanks
Kawasaki part number 27008-1103 was used from 1988-1995. From 1996-2007 the OEM Kawasaki blank is part number 27008-1173. The 1173 will also work in older bikes, but you can't use the earlier key (1103) for model years 2000 and newer.
Dealers typically ask well over $10 for Kawasaki key blanks, but there is no functional reason to get an "official" Kawasaki key. You can find them cheaper at places like Bike Bandit or Ron Ayers, but unless you're ordering other stuff at the same time, shipping charges will make them more than a dealer. The OEM key is nickel-plated brass (as are all the other keys mentioned here) with a plastic-coated head.
Model year variances
Starting in about model year 2000 Kawasaki changed the internals in the ignition switch, necessitating a different key blank. For the technical stuff on this change, see Locksmith Ledger. Any of the key blanks mentioned in this article can be used in bikes older than 2000, but there are specific requirements for model year (roughly) 2000 onwards. Keep reading.
1999 and older bikes
Short version: The Ilco X103 should be readily available. It fits your bike and is inexpensive. The Silca KW12BP will also fit without modification, as will the OEM #27008-1173 and JMA KAW-3. The Ilco X266 will work but needs to be modified.
2000 and newer bikes
You can't use key blanks designed for the older models in your post-1999 bike without modification. Keys that will work on 2000-07 models without grinding, filing, or swearing:
The Silca KW12BP has a black plastic head like the OEM key. It is 3mm longer at the top but is functionally identical. Unless you held it against the OEM blank you wouldn't be able to tell the difference. The KW12BP may be a little hard to find; you'll probably have to look for it online. Try My Security Pro.
Silca's KW16CP is a little too long, which is unnecessary for what is needed; it will stick out of the ignition further than the other choices. If it's all you can find, though, it will work and is the recommended later-model key at motorcyclekeys.com.
Note: A variation of this key is called KW16CP-SI, for nickel plated steel. Steer away from this, as some people have had a hard time finding anyone to cut it, even though it is listed as being able to be cut by a standard machine.
Similar in appearance to the X103, but it has enough side milling (unlike the X103) that it will fit any year of EX250F. JMA blanks can be hard to find in the US. Try Mr Lock.
These photos compare the KAW-3 to other available blanks:
The least expensive and most common key choice for the EX250F. This is also marked as KA14. Slightly shorter than the OEM key and is all-metal, with a head profile significantly different in shape. The length reduction is in the head end of the key. The functional parts are the same as the OEM blank.
Note: There are two Ilco lines: Ilco USA and Ilco Italy (aka ORION). You're looking for Ilco USA. The Ilco Italy brand has a key marked KA14, but that key is not remotely related to any Ninja 250 key.
Modifying the X103
The problem with the X103 on bikes after 1999 is that the key doesn't go down into the ignition switch far enough; it gets too wide to go all the way in. (Technical term: It doesn't have enough side milling.)
You can remove the extra material with a bench grinder or dremel (or let your locksmith do it). There are blanks which will fit without modification, but if you need a key now and all you can find is this one, modifying it isn't very difficult. Any competent locksmith should have no problem.
The Ilco X266 (also marked KA16) will work in the EX250, but it's really not the correct key. The proper blank (X103) is common enough. On the other hand, the modification required is easy for a locksmith to do, and if you have to choose between using an X266 and not getting a key made, you might want to go this route. Once the key is modified, it will work. It won't work at all in unmodified form. If you like, show this section of the FAQ to the locksmith for reference.
The X266 is not listed for the Ninja 250 but rather the Concours. This blank is also all-metal, but its shape is the same as the OEM key. The problem with the X266 is that there is a small ridge on each edge that prevents the key from being fully inserted into the Ninja 250 lock cylinders. The amount of interference is fairly small (less than a millimeter) but that is enough to cause problems. Without a minor modification to the key, an X266/KA16 blank cut to fit the fuel filler cap, seat, and helmet locks will not work in the ignition because the side ridges prevent it from inserting fully into the lock cylinder. Of all the locks on the EX250F, the ignition is the deepest.
Here's a closeup of the ridge in question:
You can see where the ridge interferes (seat lock cylinder shown):
The modification of the blank is to use a file or other tool to remove the ridge on each side.
The critical dimensions of the aftermarket blanks are identical to the OEM Kawasaki blank, with the exception of the metal removal needed on the X266/KA16 and X103/KA14. The thickness and width of the part that inserts into the lock cylinder are the same. The most important dimension is the length from the tip of the key to the shoulder step (20mm). The reason for this is that the ignition, helmet, and seat lock cylinders rely on the shoulder stop to determine insertion depth, whereas the gas cap has an internal stop such that only the end five of the six tumbler positions are used. If that 20mm length were to change, then a key cut for the other three lock cylinders would not work for the gas cap, and vice versa.