RPM - Am I imagining things?

[Notforhire]

I go more by how my engine sound and never run full throttle

Sounds good to me. I bush hogged for about 15yrs with a Farmall C with no tach.

 

[jshwhite]

I'd check other tractors too see how accurate they are. A couple hundred rpm one way or the other isn't really an issue, I'd be surprised if it wasn't some what a " designed in feature " too keep operators from over speeding the engine

Is the rpm discrepancy constant thru the rpm range ? Or just at full throttle ?

I had the thought of a designed-in feature, but this is a new development - it didn't used to be this way. There is a discrepancy throughout the rpm range, however, it is not a constant difference. At idle (about 900 rpm tested) it shows almost 1100 rpm on the dash. At 2500 tested (540pto) it shows about 2900 on the dash.

It's usually always the tachometer and rarely the other end.

I go more by how my engine sound and never run full throttle

Yes, I certainly go by sound and never run full throttle either. However, I do run a lot of pto-driven implements and I like to at least be able to know I'm running 540 rpm. On this tractor 540 is 2500 engine, and I just don't really like seeing 2900 on the dash when I know that's not what I'm running

Have you verified that it is intermittent? ... If so it may be vibration related - a load and rpm function. Try damping the tach body w your hand when the rpm offset occurs.
larry

It originally was an intermittent problem, but it is now constant. As I mentioned, it used to be accurate. Then I started noticing it didn't sound "right" occasionally. It got more and more frequent over a few days, and now it's full time.

So, now what? Bluegill, you think its the tach? Ouch, those run over $400. Any other thoughts from anyone? Thanks for the help guys.

 

[SPYDERLK]

I had the thought of a designed-in feature, but this is a new development - it didn't used to be this way. There is a discrepancy throughout the rpm range, however, it is not a constant difference. At idle (about 900 rpm tested) it shows almost 1100 rpm on the dash. At 2500 tested (540pto) it shows about 2900 on the dash.



Yes, I certainly go by sound and never run full throttle either. However, I do run a lot of pto-driven implements and I like to at least be able to know I'm running 540 rpm. On this tractor 540 is 2500 engine, and I just don't really like seeing 2900 on the dash when I know that's not what I'm running



It originally was an intermittent problem, but it is now constant. As I mentioned, it used to be accurate. Then I started noticing it didn't sound "right" occasionally. It got more and more frequent over a few days, and now it's full time.

So, now what? Bluegill, you think its the tach? Ouch, those run over $400. Any other thoughts from anyone? Thanks for the help guys.

Weld it.
larry

 

[Bluegill2]

So, now what? Bluegill, you think its the tach? Ouch, those run over $400. Any other thoughts from anyone? Thanks for the help guys.

From my past experience, a tach that doesn't read accurate, turned out to be a bad tach. But at $400, I'd be looking for something else too. Maybe a drop of oil in the back of the tach, like was mentioned earlier.

 

[jshwhite]

Weld it.
larry

Hahaha...laughing...laughing. That was a good one! I guess my signature doesn't apply to everything ...sure wish it applied here though.

 

[jshwhite]

From my past experience, a tach that doesn't read accurate, turned out to be a bad tach. But at $400, I'd be looking for something else too. Maybe a drop of oil in the back of the tach, like was mentioned earlier.

I did pull it out on Friday and cleaned it then oiled it - put it back in this morning and still no luck

Yeah, at $400, I think I might just have to deal with it for now. Originally I was in a hurry to get it fixed because I was thinking it affected the hour meter since it is a mechanical meter (faster rpm reading = more hours), but after pulling it apart and looking at how it works, I think the hour meter should be unaffected since there are two separate mechanisms there. The gear drive for the meter is behind the tach part, so it shouldn't matter. Am I thinking correctly here? If so, and it's not affecting the hour meter, I may just need to wait until $400 drops out of the sky...or something like that

 

[Deano]

See if you can borrow someones tach and make sure that is it. If it is, wait for the money to fall from the sky like you said!!:thumbsup:

 

[Bluegill2]

The tach should not effect the hour meter on these newer tractors. But I'm not 100% on that.

 

[Notforhire]

Take a look at your alternator and see if it has an AC post. Those are usually used for electronic tachs. You could use one temp if you wanted, they are usually pretty cheap.
Another way would be to mark your hand throttle where you have 540 rpm, while checking with your hand held tach.