M max engine rpm

desperado812 · Aug 12, 2015

I have a M that I have been running for about 8 years. I have seen that max idle RPM is 1450. To get 540 RPM on PTO I have to run the engine at 3450 RPM. Its been running fine there and use it often to mow. Does anyone know the max RPM other than the 1450 which is the idle speed. Thanks for any info

David G · Aug 12, 2015

You sure about those numbers?

buickanddeere · Aug 12, 2015

(quoted from post at 18:02:49 08/12/15) I have a M that I have been running for about 8 years. I have seen that max idle RPM is 1450. To get 540 RPM on PTO I have to run the engine at 3450 RPM. Its been running fine there and use it often to mow. Does anyone know the max RPM other than the 1450 which is the idle speed. Thanks for any info

Assuming you want to obtain 1000rpm from a 540 rpm machine by over reving it.
Centrifugal force increases by a square of the rpm. At 2051 rpm the force on the flywheel and clutch has doubled.
Unless you add high pressure valve springs and a billet steel clutch. You tractor will look like this at about or above 2500rpm iirc.
Is there an aftermarket tach on the M, set to Two Cylinder mode ?

https://www.youtube.com/watch?v=y7gKbk0jyyM

rustred · Aug 12, 2015

some thing not making sense here. 540 pto is max. idle speed of 1450 rpm on engine.the idle speed of these engines is about 400 rpm as not to get run on when tractor is shut down. sure you can boost the rpm up some at the governor, but 3450 dont make sense. you will have metal pieces flying around.... unless u have a typo error.

D Slater · Aug 12, 2015

If you have run a M engine for 8 years 3450 RPM and it's still together you better play the lottery.
At 1450 RPM the PTO should be turning 537 RPM. At no load full RPM the PTO should turn 596 RPM at close to 1600 engine RPM. Idle PTO speed 185 RPM. Better check your RPM gage.

old · Aug 12, 2015

As per the I-T Ih-8 low idle is 425RPM. Engine no load RPM is 1595 which is max RPM is should be turning with out a load. Once loaded the gov will do it best to keep it at the 1595. If it is truly spinning 3450RPM your lucky since that is more then twice what red line is for that engine

bill mart · Aug 12, 2015

love the shrapnel at the guys feet. Bill
1206

desperado812 · Aug 12, 2015

That's what I have been told but that is the engine speed and the governor will speed the engine on up if it gets in deep grass. My H runs at 3650 max engine speed and I have been told about the Max and was wondering myself but I use on a regular basic and it has been running that since I owned it for about 8 years and that's a tach on the engine and one on the PTO. Borrowed them from work so two independent tachs. I guess I am just lucky. Thank you for your time

desperado812 · Aug 12, 2015

Yes sir. That is two independent tachs. One on the PTO and one on the engine. Borrowed them from work and they are calibrated tachs. My H runs at 3650. The M is used on a regular schedule for mowing, Guess I am just lucky. Thank you

desperado812 · Aug 12, 2015

No Sir. these are the magnetic tachs that I borrowed from work. You put a piece of tape on the flywheel and one on the PTO. They are calibrated tachs and checked my M rpm to the H, the H runs a little faster at 3650. I use the M on a regular basics. It has run that since I owned it about 8 years now. The reason I checked it was it seemed to running a little slow but I guess not. does a good job at handleing deep grass and the governor will speed it up from there if it chokes down. Thank you much

D Slater · Aug 12, 2015

Governor work or a solid linkage inside the housing would be needed to get that kind of RPM. Can't believe the flywheel is still on the crankshaft. Was this a pulling tractor at one time? Has someone put a reduction gear box ahead of the transmission? Is this a 4 cylinder Farmall M engine in the tractor?

David G · Aug 12, 2015

You sure those numbers are not 2000 RPM high?

An RPM of around 1300-1700 is normal for an engine of that vintage.

gene bender · Aug 12, 2015

You have something mixed up real bad as the M engine will come apart at 3450 RPM better recheck as nobody is going to believe your story most of us on this site just have great knowledge of internal combustion gas fired engines that were used in tractors so you aren't fooling us when you say a stock M Farmall engine will run 3450.

John M · Aug 12, 2015

Of the thousands of Ms and Hs in the world, none of them have to be cranked up like that to get the right rpms on the pto. One of 3 things come to mind, 1. You have some kind of aux gear box that's slowing down the PTO, 2. your using your RPM gauge wrong, 3. Your playing a joke. With the number of responces telling you your wrong, your not using your RPM gauge correctly.

Nebraska Kirk · Aug 12, 2015

(quoted from post at 18:53:01 08/12/15) Yes sir. That is two independent tachs. One on the PTO and one on the engine. Borrowed them from work and they are calibrated tachs. My H runs at 3650. The M is used on a regular schedule for mowing, Guess I am just lucky. Thank you

There is NO WAY your H is running 3650 and your M 3450! The tach is wrong or you are reading it wrong. As has been previously stated, the no load high RPM on both tractors is 1595 and rated load RPM is 1450. When the engine is running at 1450 RPM the pto will be turning 537 RPM.

K Effective · Aug 12, 2015

Tachometer as you are using will read correctly on multiples of the actual speed, thus 1500 rpm also shows good at 3000 rpm and 4500 rpm. Your tractor is most likely max rpm at 1725, and reading 3450.

old · Aug 12, 2015

NO WAY!!!!!!!!!!!!!!! Both an H and an M would fly apart if you spun one up to over 3500RPM they are not made to do more then around 1500-1600 tops and if they go higher they will explode flat out no way what your reading them at can be correct since that is like I said before over twice what red line is.

Steve@Advance · Aug 12, 2015

If you are seriously doing this, be aware you are straddling a potential bomb that can seriously injure, even
kill you or a bystander!!!

Janicholson · Aug 12, 2015

A borrowed tach that is wrong is just that. the issue id that the engine is not running at that radical speed. the PTO shaft tach is correct, but the magnet, calibration, or other factors are at play. The gearing between the engine and PTO on either tractor is fixed, and as you indicate, not slipping. Just ignore the issue and run them they are OK.

buickanddeere · Aug 12, 2015

(quoted from post at 20:59:57 08/12/15) No Sir. these are the magnetic tachs that I borrowed from work. You put a piece of tape on the flywheel and one on the PTO. They are calibrated tachs and checked my M rpm to the H, the H runs a little faster at 3650. I use the M on a regular basics. It has run that since I owned it about 8 years now. The reason I checked it was it seemed to running a little slow but I guess not. does a good job at handling deep grass and the governor will speed it up from there if it chokes down. Thank you much

A fundamental lack of understanding here. A "magnetic " tach does not use reflective tape.
As several other posters have also stated. There is an indicated doubling of the true rpm occurring.
Is there two pieces of reflective tape on the flywheel?

Owen Aaland · Aug 13, 2015

I want that H. That tractor should easily do 40 mph.

Brown Swiss · Aug 13, 2015

I have this image in my head of an M going down through town passing cars left and right. LOL If that is correct, (and that is a mighty big IF) might want to wear a brain bucket.

1206SWMO · Aug 13, 2015

As others have said theres way your M is turning anywheres close to 3450 rpms,not even 2000 rpms.......Heres what an M
sounds like that runs at high rpms..
High RPM Farmall

Blackhole49 · Aug 13, 2015

One just has to wonder how many times a guy has to be told he is wrong before he realizes he is wrong.

GordoSD · Aug 13, 2015

Your tach is set for an 8 cyl engine and is reading double what the 4 cyl is turning.

CenTex Farmall · Aug 13, 2015

There was an M I saw once or twice at pulls that used the stock block and turbo on alcohol. He buzzed that thing up pretty high. Sounded weird. It was very tempermental.

Obviously, to make that happen he used some $$$ and then some $$$ and also a little of $$$$.

RN · Aug 13, 2015

'borrowed from work tachs' OK, what is exact make and model of those tachs and what does a IHC tach designed for the IHC engines, properly attached read by comparison? A M 1450 rpm reading is NOT a idle reading that is close to the original running speed spec for belt and PTO use under moderate load. Go to the local speed shop or small engine repair/garden tractor shop and get a ignition induction tach and clip it to the coil wire or number one spark plug wire as the instructions indicate, set it to the proper cylinder setting and check what it reads. A M engine depending on fuel, year is governed at 1500 to 1700 rpm- a few commercial engines with hydraulic loads set for 2000 rpm, a few generator rigs set for 1800 rpm. I used to use a M growing up, the tweeking of governor to 1700 rpm after the altitude pistons installed was for plowing at times. RN

oc-18guy · Aug 13, 2015

At that rpm it would not last 8 seconds, let alone 8 years lol. it is way to early or late for an april fools joke!

M max engine rpm

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