Carburetor 1950 8N

Goldtractor

New User
I put new carburetor on my 8N. The problem I'm having is that it surges. When I put a good load on it will smooths out and starts running better but when it's running without a heavy load it surges. I did some adjusting to the carburetor that seem to help a little. Maybe I need to do more adjusting? Does anyone have any ideas?
 
When it surges, does pulling the choke part way out help?
If so it is running too lean and could possibly be adjusted.
If it makes it worse then it is too rich. Still could be adjusted.
New carb? What kind is it?
 
Why did you replace the carb? I would rebuild the old one or have it rebuilt before i bought an aftermarket one.
 
Was running very rich, had no power and would not adjust. Figured by the time I bought the parts and cleaner and took the time it was easer to just buy a new one and put it on and be done with it.
 
It doesn't surge when idling. It almost acts like the governor is making it surge when I am running it mid throttle.
 

I would like your old carb if you are interested in parting with it. You can contact me to discuss options at my gmail address: jimpsc at gmail dot com.

Jimps in A
 
I think I better hold on to it. I have another 8N and in time I will rebuild it. But thanks for the offer. If I change my mind I will let you know.
 
(quoted from post at 12:47:41 11/10/16) I think I better hold on to it. I have another 8N and in time I will rebuild it. But thanks for the offer. If I change my mind I will let you know.

No problem. I have a few 8N's and I like to have a few carbs ready for service.

Thanks,

Jimps in GA
 
"It almost acts like the governor is making it surge"

It probably is, because the carb needs to be adjusted.
They will lope or surge when running too lean or way rich.
That's why I asked if partial choke helped or hurt.
So we'd have an idea on which way to adjust it.
 
(quoted from post at 10:14:07 11/10/16) "It almost acts like the governor is making it surge"

It probably is, because the carb needs to be adjusted.
They will lope or surge when running too lean or way rich.
That's why I asked if partial choke helped or hurt.
So we'd have an idea on which way to adjust it.[/quot


I will try the coke today and let you know.
 
I like to adjust my 8ns like this:

Before starting I adjust the main jet out from full in 2 1/2 turns. Start tractor and let it warm up. when at normal operating temp, I go to full throttle and then adjust the main needle in until the engine starts to falter, then back it out 1/4 turn. may have to back out a bit more if needed to run right under a load. Just what works for me. I have never been a fan of 2 turns out and leave it that some on here post. every carb and engine is different.
 

There is a good diagram of the carb in the FO-4 service manual which you really should have if you own one of these machines.

The only dumb questions is the one not asked.

There are two jets on the carb, the larger one on the front end of the carb is the main jet. the small one is the idle jet and it only controls air at an idle. the large one is in for lean and out for richer. the idle adjustment is the opposite.
 
42437.jpg
 
The large, down pointing one opposite the air hose.
The small angled one on the side is the idle air adjust.
The one on the linkage in the back is to adjust idle speed.
 
Ok, partial choke didn't help so probably not too lean.
Are you seeing black smoke out of the exhaust pipe?

I posted this earlier today for Terry.
Maybe this adjustment procedure will help.

I set the main adjuster out 1 1/2 turns, start the engine
and let it warm up, then run it at near full throttle and turn
the main adjuster in until the engine sound changes.
Back it out 1/4 turn from that point and leave it for now.

Idle the engine down, then snatch the throttle open.
It should accelerate immediately and smoothly.
If it coughs, open the main screw 1/4 turn at a time until
it doesn't cough. If you get past two full turns something's
not right in the carb. I have seen them run Ok at 2 1/2
or 3 full turns but they weren't quite right inside.

Next set the throttle at idle and adjust the speed to
~400-450 RPM. Without a proofmeter close counts.
Once there, adjust the idle adjuster for smooth idle.
Usually somewhere between 1/8 and 1 turn.
Remember that this adjustment changes air flow so
it is backwards. In is rich on this adjustment.

I then repeat the test of snatching the throttle open
from idle. If the tractor is running well enough at this
point, do the same test under load.

You may find that each adjustment affects the other so
you have to do them all several times to get it dialed in.
 

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