How do I check my 9n RPMs

I just put a new carb on my 9n and know my top engine speed needs to be 2000-2200 RPM or 800 PTO RPM but how do I measure the engine speed? There is no way that I know of to hook up a tachometer so where does that leave me?
 
If you really, really need a tach, scroll down the page a bit. The solution there was something called "Tiny Tach".

I've got 2 N's w/ tachs & 2 w/o. I can't see that one is that important once you figure out a few things.

Set the carb for the lowest idle (if you don't know how to do that, just ask). If the carb is ok, you can get them down to 350 rpm.

For high speed, it takes some work w/ the governor. That's best covered in the I&T FO4 manual (tip # 39 at the link below).

For the PTO, rule of thumb is 3/4 throttle gets you 540 PTO RPM. Or, you can do the math. PTO RPM = Engine RPM divided by 2.75. Max engine speed is supposed to be 2200 RPM. 3/4's of 2200 RPM is 1650 RPM. 1650 divided by 2.25 = 600 RPM. Close enough for government work.


Remember, N's were made for 11 1/2 years w/o a tach. The average farmer figured it out!
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My point (which I clearly failed to make) was that you do not need a tach on an N to set the idle, high speed or PTO speed.

It won't idle much lower than 350 rpms, the governor, set properly, will not allow the engine speed to exceed 2200 rpms & pto speed of 540 rpm's is at 3/4 throttle.
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(quoted from post at 21:35:08 09/27/09) My point (which I clearly failed to make) was that you do not need a tach on an N to set the idle, high speed or PTO speed.

It won't idle much lower than 350 rpms, the governor, set properly, will not allow the engine speed to exceed 2200 rpms & pto speed of 540 rpm's is at 3/4 throttle.
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I've never needed to know that on my '49 8N front mount (made like your 9N).

It might be just a [b:9aca985d08]little[/b:9aca985d08] more important on a side mount, and setting the timing with a timing light, due to the centrifugal advances.
 
You didn"t say if your 9N was 6 or 12V. like Bruce said you really don"t need a tach. You can go by the feel and sound. If you don"t want to add non original stuff and your N is 12V you can get one of those old test meters that they used to use on vehicles with carburetors. You know the ones with a jungle of different wires used to check the Batt., dwell, timing, rpms and such. I have an old sears model and it works good. I"ve not checked but it might cover 6V as well. I"m sure E-bay has'em.
 
if you google search for photo tach they can be bought for $20 or less on ebay and amazon. I got mine from harbor freight a few years back. stick on some reflective tape and aim the pointer at it.
 
(quoted from post at 16:33:08 09/27/09) I just put a new carb on my 9n and know my top engine speed needs to be 2000-2200 RPM or 800 PTO RPM but how do I measure the engine speed? There is no way that I know of to hook up a tachometer so where does that leave me?
understand that with enough experience, you can tune a tractor by ear, but while experience does start when you begin, it can take a while. So until you get there, a dwell tach meter could be handy.

Sounds like you want a LCD Automotive Multimeter with Tachometer Kit You connect it to the ignition... somewhere (just used one 50 years ago and forgot where to hook it up). I still have one, it was easy to use, but I lost the directions. They used to sell dwell tach meters but these days it looks like some digital multimeters will measure dwell and rpm.

The one in my harbor freight link is a clearance sale, item, so it is not going to be a good link for long. HF also has a photosensor type that needs to look at a a piece of reflective tape, so it would be good for the PTO or anything else that spins, providing the tape will stick and you have a clear shot at the crankshaft pulley.

This post was edited by Dave G9N on 01/23/2023 at 05:53 pm.
 
(quoted from post at 17:02:59 09/27/09) I get all that but what do I use to actually measure thr RPMs?

I use the free App "strobily" on my android smart phone. Google how to use a strobe light. A piece of reflective tape on the PTO shaft is all you need to find 54O RPM. Which, Using Bruce's math translates into engine RPM.
 

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