That's good enough.
Some people go to the trouble of buying infrared temperature gauges and all that paraphernalia but I think if you just use your finger touch is close enough. Even when you start by using a temperature gauge, in the end you will build experience and be able to tell by touching if you're too hot. If you can't touch your motor after a few laps (you don't need five minutes, just five laps) for at least three seconds or some such, you're too hot. After a while you'll get your finger "calibrated"! Then again things start smelling funny when they get hot, hehehehe!
Speed will tell you when you're too slow (low geared).