Is 2875 RPM too much?

ratface

Member
Since replacing my worn throttle plate and making lots of adjustments I finally got the throttle lever to behave pretty good in each quadrant. The tractor now idles nice at low Quadrant with good upsurge of power on the last quadrant of the face plate. I remember reading that the max RPM is 2600. My tractor is topping out at 2875 rpm, throttle lever all the way over. Is the 275 rpm that big of deal, quite frankly I kind of like it?
 
Max RPM is supposed to be 2200 RPM, not 2600.

I'd question your tach.

As long as you have good oil pressure, I wouldn't worry about.
75 Tips
 
It's a 1949 8N FM. The Tach is one of those hand held point and click Tach's with a piece of reflective tape on the fan housing. Is 2200 at idle?
 
In 1942 when the tractor engine was available in pickups it was rated at 40 gross HP AT 3200rpm.
The valve springs were 9N also but cam had a different # as it had a fuel pump drive lobe.
4.55 would be standard gear in 42 for that engine.
 
2875 is max RPM, I didn't measure the low side. I will do that next time I can work on it. The gizmo for measuring is pretty cool, just point and click. States the margin of error is +- .05%. I think I will measure a known value to see if this thing is accurate. The tractor just sounds right where it's at. Your point about low rpm is well taken, perhaps it's too fast from the
git-go. I've fooled with so many adjustments I might not have put the idle screw back to where I started?
 
(quoted from post at 01:56:52 07/09/14) 2875 is max RPM, I didn't measure the low side. I will do that next time I can work on it. The gizmo for measuring is pretty cool, just point and click. States the margin of error is +- .05%. I think I will measure a known value to see if this thing is accurate. The tractor just sounds right where it's at. Your point about low rpm is well taken, perhaps it's too fast from the
git-go. I've fooled with so many adjustments I might not have put the idle screw back to where I started?

Checking you device with a known RPM is a good idea. I think 2875 would sound way high for a 8n. I got one also think I will go and check my 50 that has a tack on it.
 
I put the tape on the crankshaft nut and as close as I could tell I was getting a bit more than the tack. I only get a bit over 2000 RPM at max and that works for me.
The I put some tape on a 1725 RPM electric motor and I was getting about 1755, so it looks like mine is a bit high. Harbour freight special.
 
(quoted from post at 12:34:12 07/08/14)
The I put some tape on a 1725 RPM electric motor and I was getting about 1755, so it looks like mine is a bit high. Harbour freight special.

The 1725 rpm on the electric motor nameplate is at full load. The actual speed decreases as the load increases. 1800 rpm is the synchronous speed of your motor, so 1755 rpm doesn't sound unreasonable if it is lightly loaded (or no load at all).
 
(quoted from post at 03:28:08 07/09/14)
(quoted from post at 12:34:12 07/08/14)
The I put some tape on a 1725 RPM electric motor and I was getting about 1755, so it looks like mine is a bit high. Harbour freight special.

The 1725 rpm on the electric motor nameplate is at full load. The actual speed decreases as the load increases. 1800 rpm is the synchronous speed of your motor, so 1755 rpm doesn't sound unreasonable if it is lightly loaded (or no load at all).
Thanks, I learn something every day. The motor had a light load on it!
 
So that same engine is capable of 3200 rpm? Which is really what I'm after, which is at what point does some damage occur?
 
(quoted from post at 16:06:15 07/08/14) So that same engine is capable of 3200 rpm? Which is really what I'm after, which is at what point does some damage occur?
 
<at what point does some damage occur?>

Typically about 1 second before you hear it. Just time for you to say "Oh dear, that's not good". (or words to that effect).
 

If you can hang on and stay in the seat its not to much.... The gov gear came lose from the shaft on one of my N's it took off like a rocket... I was almost done but it was not EZ to manage the extra un-governed power... The gov keeps it manageable at most any speed..
 
(quoted from post at 16:41:55 07/08/14) <at what point does some damage occur?>

Typically about 1 second before you hear it. Just time for you to say "Oh dear, that's not good". (or words to that effect).
...and if hard of hearing, they sometimes give a visual:

 
Wow, I usually operate at 540 rpms at the pto which is idk, about maybe 1400? I really don't like to go much higher than that, it sounds like its gonna take flight. I don't really know what I'm talking about, but N's don't have harmonic balancers right? Isn't that the reason for the lower rpm range, the engine will shake itself apart?

What about the pulley ratio? Is it 1:1
 
To check your hand held optical tach, point it at a florescent light. It should read 7200+or-, if your tach goes that high. Good way to check them.
 
Seems like a simple question to answer. If it was an engine in good shape probably not. On the other hand if it's worn out I wouldn't take my old tractor engine that high because it can cause additional ventilation as JMOR stated.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top