1948 ford 8n bogs under load

[blakefords]

I've got a '48 8n 12v that ran and cut with a 5ft finish mower but did not hit high rpms. Over 7/8th of throttle the tractor pops and back fires. When I push the clutch in and free spin the tractor ran good. After messing with the main jet to add more fuel, it turned into a crank no start scenario. Checked spark on all 4. (Bright and blue) verified plug order(also correct) verified fuel flow(strong) and set the carb setting 2 turn out main, 1/2 turn idle mix.

I ended up pulling the carb(absolutely clean and zero rust) and replaced the distributor and cap with one the prior owner had and this made it fire up and run.

Now the tractor runs but spits and back fires and won't do much over half throttle unless I creep it up, pops and lugs with hard acceleration and choke makes it die.

This tractor has been garage kept for some time. This issue started after letting it set in my field for 2 months cutting with it a few times.

 

[Jim L WA]

Sounds like your tractor is punishing you for leaving it out in the field. My thoughts are leading to distributor, not the cap and rotor, but I would check the points. Look for pitting and check the gap, .015. Check the bushing, is there any side to side movement of the shaft? Then I would take a look at the centrifugal advance weights. Are they clean and free to move? Then of course reset the timing.

 

[joeysmith]

How long since the air filter has been serviced?
Be the first place id look

 

[DN-N-TN]

From the picture----it looks like an aluminum carburetor---that is the characteristics of the Chinese carbs you described. I'd find me an original and rebuild it, then adjust the high speed screw at full throttle. I never like to use a six foot brush hog, or finish mower on an 8N----it's a little too much, and I found a five foot works much better, and still cuts out your tracks. Of course, that's one man opinion, and I'm sure you'll get others as well, which is fine, too. Weigh everything and do it your way, Dennis.

 

[blakefords]

How long since the air filter has been serviced?
Be the first place id look

Haven't pulled the filter. But I dropped the oil canister for it and it was crystal clear.

Completely disconnected the intake pipe from carb while diagnosing this issue as well. No running changes.

 

[blakefords]

From the picture----it looks like an aluminum carburetor---that is the characteristics of the Chinese carbs you described. I'd find me an original and rebuild it, then adjust the high speed screw at full throttle. I never like to use a six foot brush hog, or finish mower on an 8N----it's a little too much, and I found a five foot works much better, and still cuts out your tracks. Of course, that's one man opinion, and I'm sure you'll get others as well, which is fine, too. Weigh everything and do it your way, Dennis.

I've got the stock one. The marvel schebler. Didn't have time to clean it out but you are not the first person to say they prefer the stock ones.

Might be a 5ft mower. Just a guess. Yes its a little big for this Ford.

While adjusting at full throttle, when it bogs and pops do i assume this is lean and add more fuel with the downward pointing main jet(power jet)?

 

[blakefords]

Sounds like your tractor is punishing you for leaving it out in the field. My thoughts are leading to distributor, not the cap and rotor, but I would check the points. Look for pitting and check the gap, .015. Check the bushing, is there any side to side movement of the shaft? Then I would take a look at the centrifugal advance weights. Are they clean and free to move? Then of course reset the timing.

Yes lol. While building my home I don't have anywhere to park it under.

Check the bushing on the distributor shaft? Internal on the distributor or on the cam from the motor?

Timing on the front mounts are done by the slide plate on the side of the distributor that's held down by a Philips screw correct?

 

[Jim L WA]

The bushing for the distributor shaft, It is internal If it's worn you can't keep the points gap set. You're correct on how the timing is set.
But, I may be wrong about the distributor anyway. I failed to notice the after market carburetor. I would go that route first.

 

[JMOR]

I know they grate on nearly everyone here, but I have one tractor with the aluminum after-market carbs and it runs just fine as does the other 8N with original iron MS carb.

 

[Non-farmer]

I never like to use a six foot brush hog, or finish mower on an 8N----it's a little too much, and I found a five foot works much better, and still cuts out your tracks. Of course, that's one man opinion, and I'm sure you'll get others as well, which is fine, too. Weigh everything and do it your way, Dennis.

I couldn't agree more. IMO, an N does not handle 6 foot mowers well.

 

[HarryVanderpool]

I know they grate on nearly everyone here, but I have one tractor with the aluminum after-market carbs and it runs just fine as does the other 8N with original iron MS carb.

"The Junk Pile" has an aluminum carb and it works perfectly. Unlike the rest of the tractor.

 

[blakefords]

I know they grate on nearly everyone here, but I have one tractor with the aluminum after-market carbs and it runs just fine as does the other 8N with original iron MS carb.

When i bought it the tractor had the 241b aluminum carb on it and it ran good enough to spin the mower and cut it all. This slowly became an issue where I was down on power and spitting and backfiring.

 

[JMOR]

When i bought it the tractor had the 241b aluminum carb on it and it ran good enough to spin the mower and cut it all. This slowly became an issue where I was down on power and spitting and backfiring.

Carb didn't change over time.....but could get dirty over time, regardless of Chinee aluminum or iron MS.

 

[Eman85]

Carburetor can only work if it is getting adequate amount of fuel. Star with a fuel flow test.

 

[Roger in Iowa]

I've got a '48 8n 12v that ran and cut with a 6ft finish mower but did not hit high rpms. Over 7/8th of throttle the tractor pops and back fires. When I push the clutch in and free spin the tractor ran good. After messing with the main jet to add more fuel, it turned into a crank no start scenario. Checked spark on all 4. (Bright and blue) verified plug order(also correct) verified fuel flow(strong) and set the carb setting 2 turn out main, 1/2 turn idle mix.

I ended up pulling the carb(absolutely clean and zero rust) and replaced the distributor and cap with one the prior owner had and this made it fire up and run.

Now the tractor runs but spits and back fires and won't do much over half throttle unless I creep it up, pops and lugs with hard acceleration and choke makes it die.

This tractor has been garage kept for some time. This issue started after letting it set in my field for 2 months cutting with it a few times.

Remove the distributor cap and spray with WD40 thoroughly to remove the slightest bit of water from the body and cap!

 

[blakefords]

Remove the distributor cap and spray with WD40 thoroughly to remove the slightest bit of water from the body and cap!

Would that not attract dirt and sand? I know it will displace water.

 

[Roger in Iowa]

The WD evaporates. There are gaskets to keep dirt and sand out of the interior of the distributor. Only water from rain or condensate gets into the distributor.

 

[Jim L WA]

The WD evaporates. There are gaskets to keep dirt and sand out of the interior of the distributor. Only water from rain or condensate gets into the distributo

 

[Jim L WA]

blakefords, check out the post called, Carburetor Questions by NVjeff. Scroll down to the post by soaked. Interesting.

 

[Mad Farmer]

Any chance the gas (E10?) picked up water sitting in the field a few months?

When you do a gas flow test catch the liquid in a clear jar and see if there if two layers