Testing 7000 series tachometer

Is there a good way to test a tachometer? I fixed some incorrect splicing in my wiring harness, and got the tachometer to work again on my 7080, it looks like it has the correct double pulley on the Delco alternator, and it was originally a Delco system from what I was told. Currently the tachometer reads my low idle rpm is 600, and high idle is 2,200. It is my understanding high idle should be more like 2,800. Is there a way to check and see if the fault is in the tachometer or if something is keeping the engine from reaching the proper high idle?

Never used it or have it, but i-phone's have an app to measure rpm's.

That sounds like a good plan! I just checked them out, got one on the way.

all the grooves in the rest of the pulleys are all worn in after all these years belts all wore in a little  has to change the ratio a littlle bit

I wonder what kind of a nightmare it would be to try to drill,thread,mount an 8000 series pickup and wire an 8000 tach? I don't have the knowledge to do it.

I dont see how you could drill the plate on the ttractor. I changed the piickup on my 8070 and it was plenty tight. Im guessing theb 7 and 8000 series plates are the same execpt for the pickup hole but im not sure If you could find an 8000 series plate and change it??????????

Creston I can understand why you want to be correct. If we run our 390 mower/conditioner at 540 it does a much better job cutting and conditioning. A 100 or 200 rpm off and it makes a big difference on that machine.

CrestonM wrote: My main concern is keeping loaded RPMs when plowing around 2,300. Being as it's a 7080 with a lot of hours, I don't want to let the RPMs climb up around their top rated RPM. That, and I just like everything to work the way it should or it bugs me.

To clarify thats to put a 8000 pickup on a 7000 series tractor

8070nc wrote: After thinking about it the pickup has extra threads. I dont see any reason not to drill a larger holo than the pickup. Tap a plate for the pickup and put oversized mounting holes in the plate. Drill snd tap the engine engine plate for the mounting holes. That way if the hole for the pickup isnt in the right place it could be moved until it worked

If this doesn’t work for me, I’ll look into this.

I'm not so sure that the 8000 series flywheel sensor will work in a 7000 series. I was thinking that the flywheels were different. I don't think that it reads off of the teeth of the ring gear. Doesn't the 8000 series flywheel have a series of bumps or slots on the front face to give the sensor a reading?? The parts book shows the flywheels to be a common number now, but that maybe just a parts supersession .

Dakota Digital make a tach and speedometer interface that you can scale the input so the tach reads what its supposed to. Might be the simplest solution.for you Creston

SteveM C/IL wrote: You say it's high hours. I don't know what that means but if over 5000 and you don't have a history,I'd be putting brgs in the bottom end. You are capable. Just follow directions on the rod bolts. They ran at 2800 and they didn't stay together. The 8070 was turned down to 2600. I set mine to 2500.

Hour meter stopped at just over 8,900. Previous owner said it was that way when he bought it from the original owner, so I’m not sure how many hours are on it. The PO said he only put maybe 100 hrs on it the several years he had it. Someone wrote on the valve cover the valves were set at 9,800 hrs, but I don’t know how they would’ve known that without a working hour meter.

This will be a topic for another thread, but is rolling in bearings really that simple? Will the crank journals being worn out of round not effect that? I just worry a little more on a high horsepower, fast turning engine like this. I do plan to replace the fluid dampener.

Edited by CrestonM - 24 Feb 2023 at 8:19am

Creston, see if you can find a smaller diameter pulley.
Tim

It is linear: 740/600: 23% off, 2300/1800: 28% off. Close enough to say a pulley that increases the ratio by about 25% would correct the problem, if you opt to go that way.