Shifting gears on a motorcycle is a skill that can be learned and improved with practice. While I can provide you with some general guidelines, keep in mind that the optimal RPM and speed for shifting can vary depending on factors such as riding conditions, personal preference, and the specific model of the motorcycle. Here's a general guideline for shifting on a 2012 Kawasaki Ninja 250R:
Shifting from 1st to 2nd gear: As you release the clutch and accelerate in 1st gear, you can typically shift into 2nd gear around 10-15 mph (16-24 km/h) or when the engine reaches around 6,000-7,000 RPM. It's important to listen to the engine sound and feel the bike's response to determine the right timing.
Shifting from 2nd to 3rd gear: After shifting into 2nd gear, continue accelerating until you reach around 20-25 mph (32-40 km/h). At this point, you can shift into 3rd gear when the engine RPM is between 6,000-8,000 RPM.
Shifting from 3rd to 4th, 4th to 5th, and so on: As you progress through the gears, the general guideline for shifting is to do so at higher speeds and higher RPM ranges compared to the previous shifts. You can typically shift into higher gears (4th, 5th, 6th) when the engine RPM is between 7,000-10,000 RPM, and the bike has reached higher speeds, usually 40-50 mph (64-80 km/h) and above.
Remember, these RPM and speed ranges are approximate guidelines, and it's crucial to adapt your shifting based on the specific riding conditions, road conditions, and your comfort level. Practice shifting at different RPMs and speeds to find the sweet spot for your specific motorcycle and riding style. As you gain experience, you'll develop a better feel for when to shift based on the engine sound, bike response, and your own comfort and riding preferences.