800 gas runs for 2/3 hours and then starts dying

I have had this tractor for many years and know my way around it pretty good but this intermittent problem has me stumped I run it for 1/2/3 hours and it starts cutting out it seems to me that when the temp out side I"s hot and the motor reaches a sertant temp that"s when it starts. shredding grass with a small 5 ft shredder in around 95 heat out side my experience tells me that it sounds like ignition but I have replaced every thing points condenser coil etc the only thing I haven"t done is the resister that"s there before the coil side mont distibuter points at .025

I had a similar issue with a 640. I had replaced everything except the coil. I decided to change the coil. When I tried to disconnect the coil, the wire snapped. The stranded wire was apparently frayed down to one or two strands. I replaced the wire (but not the coil) and the problem was solved. A badly frayed wire anywhere in your ignition system (or even a bad ignition switch) could be causing your problem.

when it starts running bad do 2 quick tests.

1, tug choke.. if that helps.. make note. 2, stop and check spark.



if spark is weak.. then address conenctions and or coil / switch and resistor ( i personally would not use a resistor on a side mount vs just using the correct coil.. )


if the choke helped. carefeully ease open the gas cap and see if there is a vacume... don't snatch it off as gas can spray out,

Look back in the archives, there is a lot of history of similiar problems with that series due to gas boiling in the line and tank. The gas line runs behind the manifold and ethanol gas boils at a lower temp. Might not be your problem, but if gas is boiling you might consider it.

If you have not replaced the ignition switch do so.

Dean

Never thought of the switch, I think Dean might have hit the home run.

Coil on my tractor was bad, when cool it would start and run, but when the tractor got hot the coil would must have had a wire that would open up as the coil expanded, this break would kill the motor.

I just replaced the coil and it fixed the problem,
Found the problem by the old mechanics solution of replacing one thing at a time till you find the bad part.

Once I was about to have motor rebuilt because it had a knock in (1) cylinder. Until I had a old farmer friend come over and look at my tractor. He listened at the knocking sound, then started over the motor just feeling around like a Dr as he give you an exam. He felt of the crankshaft pulley, it moved, up/down a little, then ask if it normally had that many threads showing.

That was the problem, the pulley had worked loose, we tighten it up and the noise was gone.
Problem fixed!!!!!!

I,m with Jimmy Jack on this one.If you run that length of time ok,then things turn bad.Ethanol would be the first thing I would consider.I had this same sort of problem on a 640.Gas was actually rolling in the fuel tank.Don,t remove fuel cap while this fuel is hot.Vented cap is also a must in these cases.I have non alcohol gas,where lots of folks don,t if you can fine some non alcohol gas try it,vented cap also

I grew up in the 50s&60s putting many hours on an 860 as our second largest tractor and experienced the same problems then, on the hottest days.We finally came to the decision to route the gas line from the tank valve to in front of the manifold then back to the carburetor.This solved the problem caused by the gas boiling as it went down through the fuel line between the head and manifold.

I would run non ethanol first.

OK guys I appreciate all the advice this is the fist time ever using a forum its nice to have others putting there head into a problem so here"s the up date got the tractor runing better did away with the resister coil is 12v bypassed ignition switch and checked for any difference adjusted valves per spec adjusted timing per spec but. Still intermitent problems now after only a few minutes no power there is a popping coming out exhaust not loud back firing just popping when the motor comes back up after being brought down under a load haven"t checked to see if spark will jump 1/4 gap but this is what it was doing before as well starting to thank I had more than one problem going on put a lot of hard hours on it last summer in very hot temps did a little over the winter and started back hot and heavy this early spring fist job dident notice a difference but second job and so on it has been giving me problems starting to to thank carb is dirty just rebuilt it last year and have only used clean fuel but that don"t mean nothing I guess but when I pull the throttle down just sitting still it revs up quick but start working it and it starts popping and no power thanking maybe its a governor problem to never had it do this in all the years I have had it STILL STUMPED

Does pulling the choke part way out help?
Why do you have a resistor in the coil circuit?
If you buy, or already have, a 12 volt coil marked "No external
resistor required" or similar, you do not need a resistor.

(quoted from post at 03:41:51 05/19/14) Does pulling the choke part way out help?
Why do you have a resistor in the coil circuit?
If you buy, or already have, a 12 volt coil marked "No external
resistor required" or similar, you do not need a resistor.

Click to expand...

Pulling the choke out dosent help the tractor runs and works but it bogs down easily no power popping in the exhaust as the motor comes back up I have to put the clutch in a wait for it to come back I would describe it as sluggish the resistor was there actually by my father I'm gessing when he converted over from 6v I'm not shure why he had it there but it is all 12v now negative ground and remembering back now I did let it run out of fuel back on the firs job I did earlyer this spring I'm wondering if I picked up some trash in the carb only thing is I know whatit sounds like when the carb is dirty I know what it sounds like when its time for points but it has never done this

(quoted from post at 23:26:20 05/18/14)

(quoted from post at 03:41:51 05/19/14) Does pulling the choke part way out help?
Why do you have a resistor in the coil circuit?
If you buy, or already have, a 12 volt coil marked "No external
resistor required" or similar, you do not need a resistor.

Click to expand...

Pulling the choke out dosent help the tractor runs and works but it bogs down easily no power popping in the exhaust as the motor comes back up I have to put the clutch in a wait for it to come back I would describe it as sluggish the resistor was there actually by my father I'm gessing when he converted over from 6v I'm not shure why he had it there but it is all 12v now negative ground and remembering back now I did let it run out of fuel back on the firs job I did earlyer this spring I'm wondering if I picked up some trash in the carb only thing is I know whatit sounds like when the carb is dirty I know what it sounds like when its time for points but it has never done this

Click to expand...

If, when he converted it, he re-used the 6V coil like many of us
did then it would need the resistor. If it now has a true 12V coil
the resistor is not needed and may be part or all of the problem.
You could try hooking a jumper wire across it when it acts up to
see if that helps.

(quoted from post at 04:36:01 05/19/14)

(quoted from post at 23:26:20 05/18/14)

(quoted from post at 03:41:51 05/19/14) Does pulling the choke part way out help?
Why do you have a resistor in the coil circuit?
If you buy, or already have, a 12 volt coil marked "No external
resistor required" or similar, you do not need a resistor.

Click to expand...

Pulling the choke out dosent help the tractor runs and works but it bogs down easily no power popping in the exhaust as the motor comes back up I have to put the clutch in a wait for it to come back I would describe it as sluggish the resistor was there actually by my father I'm ;gessing when he converted over from 6v I'm not shure why he had it there but it is all 12v now negative ground and remembering back now I did let it run out of fuel back on the firs job I did earlyer this spring I'm wondering if I picked up some trash in the carb only thing is I know whatit sounds like when the carb is dirty I know what it sounds like when its time for points but it has never done this

Click to expand...

If, when he converted it, he re-used the 6V coil like many of us
did then it would need the resistor. If it now has a true 12V coil
the resistor is not needed and may be part or all of the

problem.
You could try hooking a jumper wire across it when it acts up to
see if that helps.

Click to expand...

I appreciate the help guys the resistor / coil etc was on and has been on until problems started developing only then did I start replacing parts like a parts exchanger I originaly thout that it was the coil running good when cold but not when hot so I changed it no change points where old so I changed them no change started thanking about that resistor being there so I got rid of it no change

146 Robinson,
You list several things that you changed. I did not see plugs on the list.
Plugs do go bad. When it acts up, try pilling one wire at a time and see if it gets worse. If you pull a wire and it doesn't then you have found a bad plug/wire/cyl.
HTH
Keith

(quoted from post at 05:02:16 05/19/14)

(quoted from post at 04:36:01 05/19/14)

(quoted from post at 23:26:20 05/18/14)

(quoted from post at 03:41:51 05/19/14) Does pulling the choke part way out help?
Why do you have a resistor in the coil circuit?
If you buy, or already have, a 12 volt coil marked "No external
resistor required" or similar, you do not need a resistor.

Click to expand...

Pulling the choke out dosent help the tractor runs and works but it bogs down easily no power popping in the exhaust as the motor comes back up I have to put the clutch in a wait for it to come back I would describe it as sluggish the resistor was there actually by my father I'm ;gessing when he converted over from 6v I'm not shure why he had it there but it is all 12v now negative ground and remembering back now I did let it run out of fuel back on the firs job I did earlyer this spring I'm wondering if I picked up some trash in the carb only thing is I know whatit sounds like when the carb is dirty I know what it sounds like when its time for points but it has never done this

Click to expand...

If, when he converted it, he re-used the 6V coil like many of us
did then it would need the resistor. If it now has a true 12V coil
the resistor is not needed and may be part or all of the

problem.
You could try hooking a jumper wire across it when it acts up to
see if that helps.

Click to expand...

I appreciate the help guys the resistor / coil etc was on and has been on until problems started developing only then did I start replacing parts like a parts exchanger I originaly thout that it was the coil running good when cold but not when hot so I changed it no change points where old so I changed them no change started thanking about that resistor being there so I got rid of it no change

Click to expand...

OK I thank I figured it out pulled carb and found water it fits the simptoms before I started looking into this problem I was having problems after 2/3+ hours of running with the tank being filled completely up before starting and it would start the popping noise first and then after awhile started dying after shutting it down for a few days and replacing things on the ignition system among other things I was putting just enough fuel in to test drive around 5 gallons or so found that after only a few minutes of run time with engine temp around 190 are so the popping would begin again less fuel in tank the quicker it was picking up the contaminants draining tank cleaning carb going ahead and getting new gaskets for carb and going to fill tank with fresh fuel and going to dump some b12 chemtool in it also we have had lots of temperature changes out side 95° to 45° and rain I keep an emergency 1gallon jug of fuel in a old plastic juic bottle for if I run out in the field I can dump that in and get back to the truck to fill up thanking that plastic bottle is probly geting some condensation in it plus my fuel jugs don't know why but I tryd turning the fuel valve under the tank 2 full turns I have been told it will save a 1 gallon reserve but it dosent also going to put a fuel gage on just thought I see what you guys thout .....PS does anybody know the right way to tune these carbs on an 800 found stuff for n.but there different not sure of the # on carb but the main power screw is on the bottom of carb ms carb I have always just tuned it by ear but always thought it could be better thanks

ok I wanted to up date this topic so if anyone is having similar problems maybe it can help out so far the water in fuel theory is seeming like it is true drained the fuel filled it up with fresh and dumped a can of b12 chemtool in it ran it for about an hour runs great thanks every body for post and help hope this helps sombody else out in future