Thursday, November 5, 2009

Gravely 812 Tractor

I mentioned the Gravely 812 that I just bought. At first glance, it looks much like the 430 I traded in for it, but mechanically it is substantially different.

There have been several distinct generations of "real" Gravely riders, plus a couple of dead evolutionary branches. Just a few words about the ones that seem most relevant, here. The first Gravely rider was a very pragmatic response from a smallish industrial company watching its market for small farming equipment disappear and the market for large residential and commercial mowers emerge. It was really more of a camouflaged Model L walk-behind tractor and sulky combination (complete with center articulation) than a rider in the tractor/car/go-cart sense. From what I can tell, few of these were made, and fewer still survive. I think it was called the Suburban or something like that. It was clever, but not what the market needed.

The second generation Gravely rider was the 400 series, of which my 430 was part. This was essentially a 500-series walk behind tractor transmission (itself an evolution of the L gearbox design), bolted into the back end of a tractor, with elaborate and stiff linkages to relocate control levers from a handlebar position to a panel between the operator's knees. The number designated an engine spec. A 424, for example, was a 12-hp Kohler. The 430 was an Onan 12. There were others, too.

Again, the 400 series was a very practical response from Gravely to the new market -- they took what they had and repurposed it, but this time in a more conventional and compelling way. The result was not particularly refined, but quite effective, in my experience. The big bronze drive gear and independent brakes pretty much made my 430 unstoppable, even when towing heavy loads of leaves around the yard -- a great choice for leafing duty in that regard. The rear tires pretty much churned away no matter the load (no belts or fluid drive to slip, and I never had a clutch give out), and if tire traction was low (say, on wet grass), I could lightly apply the appropriate rear brake for the slipping wheel, just like an ABS-based traction control system, forcing the differential to put the torque to the other wheel, which might have better traction. A little fancy footwork and it always made it up. You'll have to grant me just slightly slower response times than an ABS controller.

Anyway, it was a great tractor, and a complete beast, but the engine was let down by a bum fuel pump and a lax owner/operator, and it needs a heart transplant, now. The guy I traded it to seemed interested in slapping a Kohler on the back to replace the Onan, and selling it back to me. And maybe I'll need it back at some point. I'm actually pretty pleased that it went to the guy it did, in the manner it did. He's a guy who finds old tractors, fixes them up for short money, then sells them. With a new Delco starter solenoid, a new right axle seal, a new throttle cable and a replacement engine (which he's in a good position to find), it could readily serve someone else perfectly well. And he could make some money in the process. For my part, I got $50 off the 812 for it, and it's out of my way. All in all, something I'm content with.

But in the mean time I'm eager to figure out this new-fangled 812 model, which is a third-generation Gravely rider, and probably only 30 years or so old, vs. more like 40 for my 430. The 800 series looks all the world like a 400 series until you lift the engine cover (to which the seat bolts) and notice the entirely different gearbox sitting there. This one is a 4-speed hydrostatic transmission that I really don't know much about, other than that when you have one fool pushing a dead 400 and another fool pushing a dead 800, the fool that drew the hydrostatic transmission will easily win that race.

I really need to get out and about on this "new" 812 to see how it works, but here's what I'm hoping for:

  1. That the gearing will offer greater flexibility for picking up leaves than the 430 offered. With the 430, I had to essentially crawl around the yard in low range and high gear, spinning the blades at high speed but moving at a walking pace, to give the mower and sucker combo enough time to actually pick up all the leaves that passed under the deck each lap.
  2. That the rear hitch will be strong enough to support the trailer tongue. It looks stout, but overleveraged and undersupported. I doubt the ball that's on there is a 2", so need to check that out, too.
  3. That the transmission will be sufficiently oxen-like to pull the trailer up hills, and that the shift to a hydro didn't sissify the whole thing
  4. That the lack of independent/steering brakes won't be a problem when it comes to slick grassy hills
  5. That the whole thing will hold up long enough to do what I need it to this year with the leaves

Time will tell.

In the mean time, though, I got it running. And with a few words of wisdom and reassurance from the tractor's seller, I learned probably enough about small engine ignition systems to be dangerous. It's not what you'd call an easy starter. And neither is it what you'd call smokeless. But it runs, and if I can get the ignition points gap set a little more precisely (can't find my gap gauge), I'm sure both will improve.

Ignition points are essentially a little switch that tell the coil when to fire the spark plug, and for how long. The points gap is important because it essentially determines the precise ignition timing. Since the switch is opened and closed by the camshaft, a tighter gap will close earlier and stay closed longer than a wider gap, meaning the spark will come earlier in the ignition stroke and last longer. But too narrow a gap will make for too long a spark, and you can cook the points. I think mine are slightly wide right now, so the spark is essentially too late and short. Even so, it runs.

To get it working, I pulled off and reattached the connector to the ignition switch, installed a complete tune-up kit (points and gasket, condenser and plug -- I think I mentioned this last week), fiddled with the trigger wire from the points to the coil, messed with the choke, and ultimately resorted to starter fluid, once I had a spark. Making it run well should be relatively simple. Hopefully.

More as I learn more about how this generation of Gravely rider delivers the goods.

All for now,


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