running rough

Hi all, I have a rough running tractor, that i would not guarantee to start each time i try to start it.

It is an early 8n 6volt front mount. It has been giving me fits this summer. earlier this summer it would run great then after about an hour would sputter and die. I
checked for spark and found none. I had battery volts at the top of the coil or about 4 volts depending on the position of the points i guess. That lead me to a full tune
up. since it died after an hour i replaced the coil (now I have 2 good coils) condensor, points, plugs (autolite 437), plug wires (TSC generic kit). went through the 10
tips. I noticed that the clip inside the distributor was allowing the distributor plate to wiggle so i replaced that and now its tight. All this and I have good spark that
will jump about the 1/4 inch on the tester.

So, I crank and crank and it fired up and ran good for 1 minute then would die. let it sit, repeat. Pulled the sediment bowl cleaned the three screens, cleaned the carb. I
crank and crank and it runs decent and able to mow with it. it will mow ok then kind of loose a little power and run a little rough at times. So it isn't consistent and it
definitely has run better especially considering all of the work i've done I would expect easier starting and smoother operation that I have had before.

I notice that to get it running and keep it running, I have the main carb needle to about 3 and 1/2 turns out. the side pointing needle does little. The low idle is ok but
probably a little fast. I took the carb back apart and sprayed everything out and same thing.

It does take a bit of cranking to start, maybe a several cranks. (which i seem to have to use a battery charger everytime to get this machine running)

Does this sound like a carb issue? I just cant seem to make it through all the carb adjustment steps. once i get under 3 turns on the main needle it will die.

Also on a related question...how much play should the distributor cam have once the male tangs are inserted in the engine? the distributor itself has no side to side play as
the bushings are not that old. but I notice that when installed i can kind of rock the rotor back and forth maybe a 1/4 inch back and forth. I was wondering if those tangs
are too worn out and if that much play would affect the timing.


But I think my rough running issue is the carb having to be more than 2 turns out....any suggestions? I did not replace any jets during the carb cleaning. I just had this
fear of messing that part up.

thanks Rob

Excellent diagnostics.



You probably already know this.....but TSC is a good source for shirts and chicken feed. Not tractor parts.



Re your distributor, here are the factory specs:




Rear Bushing ID .8635 / .8640


Front Bushing ID .4373 / .4378


Shaft top .4367 / .4370


Shaft Bottom .8625 / .8630


Cam Flats .789 / .791


Cam Lobes .869 / .871

Base Tang .177 / .178


Cam Slot Width .187 / .188



re your carb, if you have the main jet screwed out fore than 2 turns, you have a problem.


Make sure the tractor is at operating temp; that usually takes 10 ? 15 minutes at idle depending on ambient temp.

Both Ford and Marvel/Schebler (assuming you have a M/S carb ) say to set both the side-pointing idlemix and the down-pointing mainjet to 1-turn as a starting point. I set the down-pointing mainjet to 1-1/2 turns and don't fool w/ it until the final step.

Then adjust the side-pointing idlemix for fastest idle; not the smoothest idle. Next, adjust the behind the carb idle-speed set-screw for very slow 400-rpms idle. Do that idlemix adjust for maximum idle at least 3-times. Make sure that you turn the screws slowly, like 1/8 of a turn at a time & wait a second or two for the engine to catch up. Take your time!

Do it like this:

1. Adjust idle mix jet until RPM increases

2. Adjust idle-mix set screw until the engine nearly stops (as slow as you can get it unless you have a tach that tells you 400 rpm)

Repeat steps 1 - 3 three times.

Remember the side-pointing idlemix is out for lean, in for rich.

If you do not have any problems inside the carb, it is easy to get the idle down to 350 - 400 rpms.

Your last step is to go back to the main jet. Remember, in for lean, out for rich. If you end up turning it OUT more than ? turn for max power (remember, you already had it 1 ? turns out) then stop right there because you have a dirty carb or a fuel problem.

Lastly, each of us has his own definition of a carb rebuild. If your rebuild did not include soaking the carb 24 hrs in a bucket of caustic carb cleaner & blowing out every orifice w/ a rubber tipped air gun, you didn't do a rebuild, IMHO. You just replaced parts.
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I notice you said, "It does take a bit of cranking to start, maybe a several cranks. (which i seem to have to use a battery charger everytime to get this machine running)" I didn't see where you mentioned the health of the battery. How many volts is there when you first try to start it? Have you checked it with a hydrometer? Does the ammeter show that the generator is charging the battery, once you get it started? I know you said you have a good strong spark that jumps 1/4 inch, but having to turn the main mixture out 3 turns might indicate a weak spark.

[i:b529c516a5]"TSC is a good source for shirts and chicken feed."[/i:b529c516a5]

don't forget chicken wire aka poultry netting. i buy a 150' x 36" roll of the stuff from them nearly annually. i keep telling myself i need to retire from the war with bunnies - but i keep planting stuff anyway, and i'm not gonna do it just to feed them.

i'd love a bobcat that considered this to be its home. the coyotes cut the rabbits way back when they moved in around here, but lately the bunnies have made a comeback.

Bruce, thanks for the specs on the distributor. that gives me something to go from. Looking at the difference between the groove on the camshaft and width of the tang I may have too much wear. Base Tang .177 / .178 vs Cam Slot Width .187 / .188 may not allow as much wiggle as i'm seeing. Plus, when setting the timing I had to have the side set screw as far toward the bottom of the groove as it would go. I'm still able to follow the timing procedure, but maybe that indicates excess wear or even a bad rubbing block on the TSC set of points. I'll measure those.

But...I think my first step is soaking the carb and see where that gets me.

Thanks!
Rob

Jim, After I charge the battery i have somewhere around 6.3 volts. Cranking it brings it down pretty quick. If i run the tractor for any length of time and then shut if off and try to restart, it cranks pretty slow and then after a few turns I have to put the charger back on. I have not used the hydrometer. I'll have to google what to do there. With all the troubleshooting over the last couple of months I have been cranking that thing a lot. But, I think it is worth checking.

I guess I should probably start looking into whether the generator is working ok. The belt seems tight so I can rule that out at least.

So i'm looking at a more thorough carb cleaning and getting a good assessment of battery health.

Appreciate your advice.
Rob

No coyotes (yet) but rabbits and squirrels and groundhogs were under total control when the neighbor had outside cats and a hawk nest was just behind the house. No, no cats, no hawks and the all the critters are back. I've shot at least a dozen squirrels in the past week. And trapped one of the at least 2 groundhogs.

Rob,

You just triggered a memory bit here with the statement about the timing adjustment being all the way towards one end of the slot. A couple of years ago, I got points from NAPA that were poorly made and required the timing to be set like you said. Those points were crap!! And I think you got low bid foreign made points just like them. Much of my tractor problems went away when I threw those points away. I complained to our NAPA store, but got no satisfaction. Corporate bean counters buy what is cheap and have them boxed up with their named boxes, and according to the store manager, they aren't about to do anything about that supplier until they have a full barrel of returns. Then they try to blame you for not knowing how to install points correctly (and I have been working on 8Ns since 1970, how could I be so dumb for 49 years??). Many parts sellers are sourcing the parts from the same crappy manufacturer.

But it also sounds like you probably have a carb problem as well. It is hard to distinguish a poor carb and a poor ignition, you may have both.

Best of Luck

Paul in MN

thanks for the comment...I'll look into another brand of points

Re the points...??.

See tips 66, 67 & 68
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thanks Bruce, This site sells the Blue streak $23 + shipping... nnalert's didn't specify a brand of their points.

Just updating the thread in case anyone looks later when trouble shooting their situation.

I replaced the points with the blue streak points and that made a huge difference. Compared to the TSC points it was like holding a toy copy in one hand and the real thing in the other. I was able to get better adjustment of the timing and the tractor is no longer losing power and sputtering.

The running and shutting off was a clog in the fuel screen in the tank on top of the shut off. I was starving for fuel because of the clog. but the power loss was due to cheap points.

I took the carb apart and soaked it in the cleaner over night. I don't notice a difference. my main screw is still 3 turns out, so I think it is time for a full on rebuild. I suspect I need to remove and replace all the jets and do another soak and blow everything out.


Hope this helps

You're welcome. Tnx for the follow up.

" Compared to the TSC points it was like holding a toy copy in one hand and the real thing in the other. " Ahhhh yes, another glowing endorsement of TSC parts!


" my main screw is still 3 turns out, "

Yep. You have a problem there.

Post back w/ results.
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