8n struggles under load

RobBruno

Member
I have a '52 8N that I can't seem to figure out recently what is going on when I start to mow. In the spring, the tractor did fine plowing and discing the garden. Since then, I have tried to mow my field and each time when the tractor gets under load with the bush hog running it starts to cough and spit like it is choking out. This is the same 5 ft bush hog I have used for years so that is not part of the change or new. It idles fine, coughs a little, but runs fine, about 3/4 throttle it starts to act up and then when you start to release the clutch to start to mow it wants to cough and cut off. When you open the throttle wide open, it coughs and sputters till it gets running full speed and then it will turn the mower and move. In the spring, I rebuilt the carburetor and I think I have had this problem since putting in the new needle valve that has the rubber tip. I have not touch the points or the timing since the tractor was doing fine before. I have adjusted the floats a couple times. I guess I have three questions, would putting the load on the tractor have any impact on the points or or the gap for the points? Could the governor be kicking in and flooding the tractor? Do you set the 1/4 inch of float height with or without the gasket on? I recently replaced the fuel bowl, fuel line, and filter that is in the top of the carburetor. It still has the same problem. I really think this is a fuel problem the way it coughs and sputters. Had the carburetor apart, blew air and carb cleaner through all the little holes. Set the air intake to a turn and half and let it sit. Looking for any other thoughts.
Thanks,
Rob
 
Always start with your spark.
Always.
Clean and readjust your points.
The problem may well be in your carb but verify your spark First to eliminate that as a possible problem.
 
spit like choke?

choke should make it gurgle to a stop.. not spit and pop.

spitting would make me think lean.

when it starts to spit, tug a lil choke.. does it help?


( ps.. as UD said.. DO check spark first.. always.. )
 
(quoted from post at 15:33:05 08/24/15) spit like choke?

choke should make it gurgle to a stop.. not spit and pop.

spitting would make me think lean.

when it starts to spit, tug a lil choke.. does it help?


( ps.. as UD said.. DO check spark first.. always.. )

I will try pulling on the choke a bit when it starts. Best I can describe it as it sputters and surges, sputter and surges, and then again feels like is choking out because the load is too heavy. I am not going through heavy grass, but when I release the clutch to get the mower going and the tractor is not in gear, it has a really hard time getting the blade turning. Then if the tractor is still running with the blade turning, when I put it in gear and go to move, it sputters and wants to quite again like it is too much of a strain on the tractor.. I will also check my points again.
 
Think I'll steal UD's line here..

Always start with your spark.
Always.
(firing order, timing, spark in all holes..all are part of the spark check)
When you have your timing light out to take a glance at the timing, clip the lead to each wire in turn and watch the light.
Does hypnotize ya a bit, but sure lets you see if things are good in spark land.

then, on to the carb (where it sounds like the problem is)
clean it one more time just to have a good baseline.
Pic that JMOR posts of the passages will help.
Then you have to adjust it. Tractors are all different, there is no one size fits all adjustment.
ok, your problem...sounds lean..
When you think the adjustments are right in the shop, take a test drive. Flat trail, 3rd gear, moving along at just above idle.
Yank the throttle all the way. Should leap forward with no stumbles. If it stumbles, a little turn out with the main mixture screw and try again.
If you can't adjust the stumble out with the big thumbscrew...back into the carb/fuel delivery..something is still wrong.
 
Thanks All, I will probably get back to it later in the weak and check all those suggestions. I will check the spark, but I don't think I have a miss cause it runs well at idle. But, again will certainly try it out.
Rob
 
I finally had a chance to look at the tractor this weekend. I first went to the points like suggested and the gap was a little wide. So, readjusted the points and got it started. Still had some hesitation to it, but did run better. Started with slight turns to the mixture screw and things improved. Start to drive and pulled back on the throttle and still had a stumble. Kept turning the mixture and was able to get most of the stumble out. I bet I had to turn it at least 3/4 to a full turn. I am not sure if that is an indication of some other problem, but I was able to mow the grass and the tractor did ok. Still has a little miss or cough to it when running, but that could be a bunch of things I guess. Thanks for the advice and help. It got my fields mowed.
Rob
 

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