Thanks for the clarification, I had forgotten the way that the "idle circuit" works on the mixer - there is no idle circuit! Of course, since an idle jet would leak propane when stopped. All gas has to come through the gas valve, and the idle mixture screw just bypasses air to lean it out. So when the flow drops too low to open the valve, sudden stall. Makes sense.
I know not to lug too slow, I was just playing around after getting it tuned up. No load and kept a close eye on both oil pressure and throttle opening. I never would do anything under load at such low RPM, and the only reason I even would take it so low was because these old tractors were designed to work at fairly low RPM by our standards. The "turtle race" at vintage events is always fun to watch. I even saw a guy swinging an extra flywheel off the PTO shaft once to keep the motor turning over at around one stroke per second.
The real fear I had was the advance catching up to me. Those guys are usually running retarded. If I got really slow and lit the fire before the crank turned over at TDC... goodbye rods.
The tractor has been working great keeping the roads clear of snow. I may have to remove the PCV circuit as it cannot consume all the blowby gas that this old motor leaks under load. It ends up spewing oil from the breather that serves as the PCV intake, despite the mesh filter inside. Maybe I should add a catch can and route that breather to the air cleaner like you would see in a more modern PCV setup.
Modern setup vs. ancient factory propane specs on tractor
Re: Modern setup vs. ancient factory propane specs on tractor
Well, this project is complete so I should post a wrap up. I never could find an air cleaner to fit the horn on my 225 - so I made a cage out of a strainer from a water pump, and a dual-density oiled air cleaner from bulk Uni-filter foam. The only thing it needs now is a little cover to shed the rain, however both the foam and tacky oil are rated for wet conditions.
All hooked up and ready to make some square bales this week.
If I slap the governor down to idle, it will stall, but if I close it to 10% and then ease it down the last notch it will idle nice and low while I'm cutting twine off bales or using it as a crane.
In warm weather it blows a little blue smoke at idle and low throttle settings. I suspect oil is getting by the rings or the valve stems (or both as the tractor is almost 70 years old). I think I'll have to move to a heavier oil than the 5W-30 that's in there right now, even though the 5W-30 should technically match the factory specs. I run 15W-40 in many of my older gas burners but I don't start them in the winter like this one.
An interesting note - Marvel Mystery Oil breaks down under exposure to UV! I had the tractor parked in the sun for a month without use, and the red oil had faded completely to dull yellow, and some sludge had separated out at the bottom.
In warm weather it blows a little blue smoke at idle and low throttle settings. I suspect oil is getting by the rings or the valve stems (or both as the tractor is almost 70 years old). I think I'll have to move to a heavier oil than the 5W-30 that's in there right now, even though the 5W-30 should technically match the factory specs. I run 15W-40 in many of my older gas burners but I don't start them in the winter like this one.
An interesting note - Marvel Mystery Oil breaks down under exposure to UV! I had the tractor parked in the sun for a month without use, and the red oil had faded completely to dull yellow, and some sludge had separated out at the bottom.