Last weekend a buddy who works doing residential repairs turned me on to an old couple who had a 3410S sitting out behind their garage under a tarp, he said they told him to take it for scrap.
He had no interest or need for a tractor so he dropped it off to me the other night.
Its been sitting for a long time, the motor has basically became a mouse condo and the fuel in the tank had either leaked out or evaporated years ago. The tires are decent, slightly cracked but they still hold air, and the entire machine has a slight coat of surface rust. I pulled back the shroud, vacuumed out all the debris, cleaned and set the points, (which looked almost new), I replaced the cracked fuel hose and filter, gave it a new plug and dumped in a half gallon of clean fuel. It started right up and ran fine, the deck works, the blades are even decent on it.
I let it run about 10 minutes and gave it an oil change, then figured I'd make a few test passes on the back lawn.
I got about three rows done and it died, but started right back up, but I needed to choke it. At that point I couldn't put any load on it, I had to be vary careful about engaging the PTO clutch or it would stall. Once engaged it ran for a few more rows then died while making the turn for the third row. This time it wouldn't refire at all, it would start to catch, then just spin. Finally, I choked it and it ran just long enough to make it back to the garage. It died again, this time it wouldn't fire up at all. I checked the spark with a screwdriver and got a bright blue spark, I put the old plug back in, no change. The engine was warm but not hot. I could hold the spark plug long enough to thread it in and out.
I tried running it on carb cleaner through the air filter and it started up but only at full throttle. I pulled the carb, and gave it a good cleaning with carb cleaner and compressed air. There was some white powder corrosion in the fuel bowl but nothing blocking any jets or the tube.
I reassembled the carb and gave it another try but it does the same thing. Each time when it died I had bright spark, this time I pulled the spark plug and checked that the plug itself was firing, which looked fine.
I then pulled a known good carb off another 10hp I have here and tried that one and nothing changed, it still dies after a few passes. The more I keep fooling with it, the worse it gets till it won't restart at all.
For test purposes I put the original carb on the other tractor and it runs fine, no issue at all.
I pulled the head because I thought I heard a head gasket leak or backfire when it stalled a few times, the cylinder walls look new, no scoring, perfect crosshatch pattern and no ring ridge. The head gasket was cracked right next to the intake valve. I also checked to see that both valves are closing hard on their seats and all looks fine there too. I replaced the gasket and gave it another test run and it did the same thing as before.
When its cold, it fires right up, (choke out, crank it up, and shove the choke in and it'll run for an hour or more just sitting there. The minute I try to drive it, it dies, it doesn't matter whether the deck is on or not. I disconnected the kill switch wire, but again, no change.
The one thing that I notice when I'm cranking it after it stalls is that it fires for a split second, then stops firing, if its going to catch, it fires right off and runs. No amount of cranking will get it to fire if it don't catch right away. With this in mind, I was thinking maybe a bad ignition switch, so I swapped it for another switch, but no change at all.
The start, for a second strong then nothing, regardless of cranking time made me think its electrical, but I've never been able to witness it not making spark, even when it won't start. Which is why I opened up the carb.
One thing I did notice is that it appeared that I wasn't the first one going through this thing, its loaded with newer parts and there was a stack of old parts laying in the seat pan behind the seat. When it dies, it just shuts off, no backfire, nothing,like the key was turned off. The machine is a bit rough from sitting but I get the impression it don't have a lot of hours, Things like the paint on the brake pedal and running boards is good, the tires show no wear, the steering is super tight, no play or worn parts, and the motor has excellent compression. The last owner told my buddy they bought it new and used it till they bought the JD 300 they're currently using, which he said they also bought new. So that puts the date when this was parked in the late 70's or so.
Any ideas? The easy to stall part of it makes me think timing or lack of fuel but I've never seen one of these big motors spin a flywheel key and still run, let along start so well cold.