854 mowing then shuts down!

[Jennifer 1,877]

Hello everyone!  Got a real puzzle here!  Husband has visited with some on here by phone, but he is getting really frustrated!  Can anyone help us with this tractor!  It will be mowing fine, then start dying off and on at different time frames!  Temperature out side sometimes seems to play a part but could be coincident.  So he has put more and more money in this and not fixed the issue!  A list of what he has done thus far! 

new Fuel line

new condensor

new points

new carb

new plug wire

new spark plug

Used fuel pump

new coil

new switch

new battery

new head gasket

soaked it with marvel mystry oil

soaked it with sea foam

removed fuel tank cleaned and blew out

cleaned sediment bowl. Brand new one is on its way

changed oil

all 4 brand new belts

 

 

 

 

[lynnmor 7,303]

Gas tank vented?

 

Tried fresh gas with no additives?

 

Flywheel tight and keyed well?

 

Was spark checked immediately after shutdown?

[Jennifer 1,877]

Thank you @lynnmor  I don't know about the vented gas tank?  Spark was checked immediately after and had great spark!  Also pulled line off to check fuel!  He said he never messed with the flywheel.  Should it be checked?

Edited July 5, 2020 by Jennifer

[The Tuul Crib 7,336]

Vapor lock ?

[lynnmor 7,303]

1 hour ago, Jennifer said:

Thank you @lynnmor  I don't know about the vented gas tank?  Spark was checked immediately after and had great spark!  Also pulled line off to check fuel!  He said he never messed with the flywheel.  Should it be checked?

Usually the gas cap allows air to come in, try running it with the cap loose with some tape to prevent it from falling off.

 

It is worthwhile to check the flywheel bolt to make sure it is tight.

[Pullstart 62,829]

All that, I was thinking the same.  Try popping the cap off as it begins to die... or even pull the choke.  If it sputters back to life for a bit, it’s starving for fuel.  A gas cap for a ‘69 C-10 Chevy works well.  It does help to modify it a bit by prying the tabs under the vent mechanism apart and removing the heavy spring but leaving the weak one... then bending the tabs back to re-assemble it.

[WHNJ701 4,165]

I has similar issues with my 854, after chasing everything, rewiring it with fresh copper fixed it

[ri702bill 8,308]

Jen:

 

I had a similar reoccurring problem with Dad's 702 - It would run fine for an hour or so, but I'd shut it off to refuel and could not get it restarted. The problem was the spark plug had enough carbon and oil that bridged the electrode gap - cleaned the plug and it fired right up. Note - it did have spark, as seen using a xenon spark checker so that left me scratching my head, the spark was grounding out at the plug tip.

 

Bill

[953 nut 55,155]

     Like @jabelman said,one of the wire may have a terminal end that is about to fail or a bad spot in the wire causing an open that is intermittent. If there is no power going to the coil there is no spark.

[squonk 41,050]

Those wires from the switch that go under the tank crack and become brittle. Same thing with the wire to the points.

 

[Jennifer 1,877]

Ok so husband had value gap check.  Have 8 and then 18 

[oldredrider 2,548]

Gap is good, but...I have a nickel bet one of your valves is sticking. 

[Jennifer 1,877]

What is everyone’s thoughts on this?  So local engine shop never looked it over but allowed my husband to question them on this issue and he was told the cam is warn down, where the rod works the points!!!!  Any thoughts???

[lynnmor 7,303]

Can he adjust the points to see if they can close and open more than specification?  If that is possible, I doubt the theory.