Rated RPM vs. Max RPM

LazyBoy · Nov 4, 2007

Newbie question, I was looking up the specs on my B21 I bought used and the Kubota website rates it's HP at 2600 RPM, however according to my tach the engine operates at 2800 RPM when I push the throttle lever full forward, is this normal? And that extra 200 RPM sure makes a lot of difference when I'm pushing it hard.

Bird · Nov 4, 2007

LazyBoy said:
Newbie question, I was looking up the specs on my B21 I bought used and the Kubota website rates it's HP at 2600 RPM, however according to my tach the engine operates at 2800 RPM when I push the throttle lever full forward, is this normal? And that extra 200 RPM sure makes a lot of difference when I'm pushing it hard.

Yes, that's quite normal. Every tractor I've used had a couple of hundred (more or less) rpm above its horsepower rating. I always preferred running tractors at the rated rpm. Even when I had the little B7100 with no tach, I did as the dealer recommended; push the throttle wide open, then back off just enough to hear a difference in the engine sound. However, in my opinion, you are not going to hurt the tractor is you want to go the full wide open. In fact, when I got on public roads, I usually did go wide open.

Jimbrown · Nov 4, 2007

First some terminology.
Rated rpm= Rpm machine is designed to operate at most times the same as PTO rpm

Goverened rpm= the max the machine should be run at. In your case 2800.

Full rpm= The max the machine is capable of. Probably 4000 + will not live long at that rpm.

It is OK to run at full goverened rpm. But probably not necessary. Personally I prefer not to run at full goverened rpm on anything except throw a way engines. Probably because I few aircraft for a good part of my life and every rev that I wasted was one I might not have when I really needed it.

cp1969 · Nov 4, 2007

Jimbrown said:
First some terminology.
Rated rpm= Rpm machine is designed to operate at most times the same as PTO rpm

Goverened rpm= the max the machine should be run at. In your case 2800.

Full rpm= The max the machine is capable of. Probably 4000 + will not live long at that rpm.

How do you get the engine to exceed governed rpm?