8N rough running

This old dog doesn't want to learn a new trick. BTDT too many times.

Nutfarmer generously offered to help. I will take him up on that if there is no local carb guy. I seriously doubt there is.

I agree, take the whole tractor in if this don't get it. In fact, my son brought the 5th wheel trailer for me to haul it in Friday night. I decided to post here before hauling it 50 miles one way.

FWIW, this unit has been down over a year now. I have worked on it on and off several times. time to fix or scrap it.
 
BTW, there are two needle valves on this carb. I do remember one or the other is bass ackward. One is CCW richer, the other is CW richer. Anyone know which is which?
 
A picture of the carb would help. On a 2barrel you will have your a/f mixture screw which usually turning out will increase air leaning the mixture. Then you will have a needle valve on your main jet. Which when you turn out increase full in the main jet. Which would effect 3/4- full throttle.
 
The OEM carburetor is a Marvel Schwebler updraft. The main jet adjustment is opposite the intake. Start at one full turn from closed. Adjust until the engine doesn't hesitate when the throttle is opened quickly under moderate load. The small screw to the outside is the idle air adjustment. Starting position is one turn from closed. Adjust at operating temperature until engine idles smoothly. The throttle adjustment screw is located on the linkage and should be set so the idle speed is about 400 rpm.

This is from the Ford Operator's Manual.

Zenith made a replacement carburetor that was essentially identical to the Marvel Schwebler.

The flow draining from the bowl seems a little light but within reason. It may be that you have some debris that is blocking the idle passages although opening the throttle should bypass that.

Another consideration; although it is possible that a substituted part could be defective, it is extremely unlikely that substituting a defective part will exhibit the same symptoms.

Karl, if you would like, I can make a photocopy of the carburetor pages from the Ford manual. PM me.
 
These units are not like a quardajet, they are stupid simple.

Take lots of photos, clean the outside then simply remove the screws and open it up.

The shat should not wobble and the butterfly should close and not allow light to pass, unscrew the idle speed screw first.

You will see little holes, blow them out.

The float has a valve, make sure it works.

Use a hose attached to carb with mouth pressure to test.

Sent from my SM-G781V using Tapatalk
 
tq60 said:
These units are not like a quardajet, they are stupid simple.

Take lots of photos, clean the outside then simply remove the screws and open it up.

The shat should not wobble and the butterfly should close and not allow light to pass, unscrew the idle speed screw first.

You will see little holes, blow them out.

The float has a valve, make sure it works.

Use a hose attached to carb with mouth pressure to test.

Sent from my SM-G781V using Tapatalk
Click to expand...
I would add, be careful in disassembly to avoid damaging gaskets. A best option is to have a gasket kit or rebuild kit handy.
 
These are super simple to rebuild, as long as you have an assortment of high quality flat blade screwdrivers and a thin walled 3/8 socket. Some mig tip cleaning wires are handy for the passages also. Would probably take a person less than an hour to clean and do a basic rebuild, longer if throttle or choke shafts are wobbly.

I would make sure I have good fuel flow at the carb inlet elbow before rebuilding though. You have a new tank, so as long as the three screens are clean and you have the fuel valve opened two full turns and more than two gallons of gas in the tank ( so you aren’t running on reserve), you should have great flow. You should be able to ditch any inline non oem filters, they really aren’t needed and slow down fuel delivery. You also said it sat out for a year, is the gas gone bad?

Here is a decent video on rebuilding.

I would add though the brass nozzles can be tricky to get out. The couple I have rebuilt, I always heat the cast iron around the jet with a propane torch before trying to unscrew, it really minimizes the risk of stripping the screw head out.
 
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