Odometer Problem on a Kubota B7800

[jodebg]

Looking at a 2008 B7800. Owner says the tachometer reads a lower rpm (appr. 1500 rpm's)
when he is running the engine at pto speed.

Is there a fix for this?

Will the tractor have clocked less hours than it would have
if the tachometer read the rpm's correctly?

 

[Leejohn]

The tach is cable ran so would say the cable is bad. Yes the hours would be lower.

 

[coldsteelva]

Odometer reads miles driven (tractors don't have them usually), Tachometers read engine speed (RPMs) and the greater the speed of the tach, the faster the 'work' hours would show on the hour meter. You could idle for 3 hours and only clock 30 minutes on the meter (as an example), but since knowledge of the engine wear, maintenance intervals and resale value are based off the hour meter you don't know what you're getting.

Buyer beware, but unless it is a really good deal, I would walk away. The tach cable can be fixed, but then you would have to do all of the maintenance immediately so that you had a starting point and known interval after that.

 

[Bird]

I agree that the tach cable is the likely problem, but I've also seen tachs not working because the fan belt was slipping. That is, if the tach cable runs off the back of the alternator, and I don't know for sure that's what the B7800 has.

 

[ericm979]

On old tractors the hour meters were driven off the tach, and would read true at rated rpm. But this is a 2008 tractor. On modern tractors the hour meter is electro-mechanical or electronic and measures the time that the ignition is on (or on really modern tractors with EFI, it's sometimes the time the engine is running). The hour meter on this tractor should be correct unless of course the owner has replaced it or disconnected it for a while.

Tachometers can be mechanical or electronic. Mechanical ones have a cable from the engine, usually from the cam drive. (Alternator cam drives are also an old tractor thing). A bad cable can cause low reading but it's often the gauge itself. While they can be rebuilt, a replacement from Kubota would probably be cheaper. If it's an electronic tach then you'd replace the gauge.

My 1992 B7100 has an electro-mechnical hour meter that is on when the ignition is on. When you turn on the ignition to turn on the glow plugs you can hear and see the hour meter ticking... the "1/10" indicator moves every few seconds.

 

[jodebg]

Thanks for the follow up.

Here is some background. The tractor is advertised with 176 hours.
When I went to see the tractor is noticed the hour meter read 131.5 hours.

The owner told me that when he runs it a pto speeds, the tach only reads around 1500 rpm's.

He is a backyard farmer (maybe 1 acre owned for house, yard and garden) with a 5' tiller, cultivator,
brush hog, potato plow, and a JD single row seeder. From what I see, he has only used the tractor for
this pto work, since new.

My concern, from watching him operate the tractor is that it appears that he runs the tractor at rpm's
that are too high for the task. While demonstrating the fel, and even pulling it our of the garage, the
engine was running too high for all.

Can this problem be caused by the owner running the tractor at high speeds when in use?

He mentioned that the tach problem recently started.

How would I repair this tach issue? And how is the the black plastic "dash cover" removed?

 

[orezok]

The "cable tractormeter" (kuboia speak) number is 35300-99343 and is about $25. It is driven off of a gearcase from the front of the engine (See attached)

BUT, be aware that if the cable is not the problem, the meter assemble 6C140-55100 is about $300.

 

[HikoJoe]

John - I'm not familiar with the B7800, but I did a repair on my Kubota B21 a couple of years ago. The B21 has a mechanical meter and the problem was at the instrument panel end. The problem and repair are described in my posting with the title "Kubota B21 Tach Cable Repair". Hope it is helpful.

 

[Jim Nelson]

When I bought my B7800 new in 2005 the dealer told me to always run it at full throttle.I ran equipment for a living all my adult life so I ignored him but had been a "backyard farmer" I probably would have listened to him.
How does this guy know what RPM's it's running at? Does it look like it has less than 500 hours on it?
If the price is right for you and the tractor is in good shape I wouldn't be afraid of it.I have over 1200 hours on mine and the engine has been great. I have had problems with the differential lock and a front axle broke because it was not properly welded when new but overall it's been a great tractor.
You can get a cheap hand held laser tach and check the pto shaft to see what it is actually doing if you're seriously interested in the machine.

 

[jodebg]

Jim-
Owner says the tach works at lower speeds. He said the tach recently started to to read lower rpm's when he ran it at higher speeds.

Looks like new, tires, paint, bucket, seat. Just very dirty from use in the garden dirt running his attachmnets.

When I bought my B7800 new in 2005 the dealer told me to always run it at full throttle.I ran equipment for a living all my adult life so I ignored him but had been a "backyard farmer" I probably would have listened to him.
How does this guy know what RPM's it's running at? Does it look like it has less than 500 hours on it?
If the price is right for you and the tractor is in good shape I wouldn't be afraid of it.I have over 1200 hours on mine and the engine has been great. I have had problems with the differential lock and a front axle broke because it was not properly welded when new but overall it's been a great tractor.
You can get a cheap hand held laser tach and check the pto shaft to see what it is actually doing if you're seriously interested in the machine.