When do hours register on the hour meter?

[jodebg]

I have 2 questions-

*When do hours register on the hour meter?

*And, what tire pressure do I fill the tires to...the psi numbers in the owner's manual?

 

[Bird]

There are two kinds of "hour meters" and I don't know which one the B7800 has. One is simply an electric clock that runs any time the key is turned on. So it registers an hour in an hour regardless of engine RPMs, or even if the engine is running. The other kind is RPM based, so it registers and hour if the engine is running at PTO speed which isn't a great deal less than full throttle. So if the tractor is only running at half throttle, it will take 2 hours for the meter to register one. My 1995 B7100 had the first kind and my 1999 B2710 had the second kind.

And yes, I'd probably run the tire pressure the manual recommends.

 

[newbury]

From an old thread:

My B7800 is RPM based (the tachometer/hour meter runs from the engine via a flexible speedometer-type cable). I suspect yours is too.

 

[MHarryE]

The old fashioned mechanical way is like the odometer on a car. It is run off a cable and counts engine revolutions. The ones I have seen say something like "hours at 2700 rpm" so it is only a rough estimate.

Newer and larger tractors have an engine oil pressure switch in the circuit. Depending on the brand many tractors were equipped with these starting about in the 60's. The hour meter is a digital timer that only gets power when the engine oil pressure exceeds a certain level, usually about 5 psi.

More modern and larger tractors get engine hours from the engine ECM - computer. Some use the engine oil pressure switch to run the display the operator sees but the engine ECM clock can only be read by having the proper software and connecting to the engine ECM buss. The ECMs with which I am familiar start counting time after the engine reaches a certain rpm.

We have 3 Kubotas. The RTV has only a timer connected to the key switch. Switch on, hours are counting even if the engine isn't turning over. Our L5740 has an oil pressure switch controlled timer. Our M135GX is fed from one of 3 computers. It tracks days, how many hours it ran that day, and how much fuel it used during those hours.

Sounds like your tractor has the oldest style, the cable. That's a bit surprising because an idle hour counts for only a half hour. Even my cheapo John Deere riding mower has a pressure switch digital hour meter.

 

[Tx Jim]

Some tractors have a sensor mounted normally on the frt engine timing cover that counts timing gear revolutions. I just checked parts schematics and my Kubota M7040 has such a sensor on RH of engine timing cover.