I have heard it called both things. Seems on my bike if the engine is purring like a kitten I cant get the bike over 25 mph,if I get it idleing at a faster rate I can get around 29 mph. with it. Not that I want to go that fast on a bicycle.

Just seems when I get the bike back on the road and I almost get it figured out where the bike performs best it breaks down again.

So maybe purring along at 18 to 20 mph is best for these things.

I almost want to try a rear sprocket with less teeth ------so I can go about 25 without the engine screaming and vibrating so much. Cept I live around a few hills and I might suffer some on the hills.

Ted