engine cutting out after warm up!!

[David Dunaway]

I"ve got a little "57 Case Round Nose 300. Been running fine all summer using a 7" finish mower on 3 point hitch, mowing about 5 acres at a time. Recently, after the tractor is warmed up and running fine the engine goes to missing, back firing. Long story short, I"ve replaced the disturber cap (which was bad btw), replaced the coil, changed fuel filter, blew out the fuel line, to no avail. It will run fine for about 5 minutes then go to sputtering. This one has me stumped, any suggestions?

 

[Buster]

Have you changed the condenser?

 

[David Dunaway]

Not yet... was debating on whether to do that. After it sits a while it fires right up and will run great for about 5 minutes, then it starts sputtering. I may try that.....

 

[Buster]

That has been my experience when they start cutting out, I would put a set of points in there while you are at it.

 

[Adirondack case guy]

Replace the condenser and points. Most of the new ones from TSC and others don't last anymore.BTDT. The tractor acts like a fuel problem, but it is a condenser going bad, or a cheap set of points or plugs,shorting out under load.
Loren.

 

[Anonymous-0]

My 700 did that after 15 mins or so. Condensor.

 

[rustyfarmall]

Wouldn't hurt to check the valve clearance gap either.

As the valve faces and seats wear away, the valves can actually move higher up into the head, which decreases the gap between the valve stem and the rockers. If the gap becomes too small, it will go away completely when the engine gets warm, and then the valves can no longer fully close, which will cause the symptoms you are describing.

 

[Anonymous-0]

I know that you really don't want to hear this. If you have done everything on the above answers to your questionit is only one thing. Sounds just like my roundnose did for a while. If you put a major load on the tractor and then it starts backfiring. Then it won't start. After doning everything above at least twice I finally took the distributor out and stuck my finger down to the cam shaft gears and felt them they were so sharp they cut my finger. The gear on the cam shaft should be approx 1/8" thick at the crest of the gears not sharp. Everytime I dropped my 10' disk and went about 30' my tractor would backfire and stop running. If I took out the distributor and reset and check timing it would fire again. What was happening was the damaged cam shaft gears were allowing the distributor to jump out of time and would be one gear slot off. That is when it started getting expensive. While you are there you might as well replace everything. I did that and haven't had one problem with timing since. Good luck and hopefully that it is only the condenser oand points. Another issue it could is the shaft in the distributer could be turning with a wobble throwing it out of time. They wear over time and lots of use.

 

[Anonymous-0]

I had a similar issue with a rebuilt 148 gas ran great couldnt be happier then started running rough backfireing, long story short it was not getting enough fuel cleared line problem went away

 

[Brokengun]

Points and condenser but before you do that grab a hold of the distributor shaft where the rotor cap sets and wiggle it. There should be a small amount movement.

I had a worn out Delco distributor that had a worn shaft that did something similar

 

[AllanC]

Check the gas tank cap. If the vent is plugged it will cause what you describe.

 

[HWess]

My 300 did that last week several times. New coil solved the problem.