What engine RPM is safe for engine?

Answer 1

Engine Revolutions Per Minute (RPM) can be "safe" at a variety of levels......depending entirely on what the vehicle is doing.

On the HIGH end:

If the question is meant to determine "how fast can my engine rev safely", the answer is, "Anything below the redline (preferably the orange line) drawn on the tachometer by the motorcycle manufacturer.

In the absence of a tach, you'll know by the screaming and wailing of your engine that you should be shifting gears.....NOW.

In these days of high fuel costs, lower RPM is better......notwithstanding the "Need for Speed"...and the desire to not blow up your engine.

On the LOW end:

If the question is meant to determine "how slowly can my engine rev safely", the answer is "As slow as it can without the engine chugging and lurching and possibly stalling....notwithstanding the possible need to accelerate quickly, which would of course require higher RPM.

It's an art and a science....with a little bit of politics thrown in on the side.