wd smoking

• Hobby farm

• Hobby farm

If you had it running without smoke before, you should be able to get back there again. Regarding cylinder compression, the last time that I tested it on my '51 WD, it was around 100 psi on all cylinders, as I recall. Do you know what operating temperature your WD reaches? Multi-viscosity oils don't thicken until they get to a high temperature, and my WD doesn't get to 170F unless it is working quite hard, or the shutters are closed.
Did you change sparkplugs when you changed oil? Are they a hot or cold plug? Have you looked at their condition since the smoking began?
It takes a little effort if you have the original hose from the air cleaner to the carb, but have you disconnected the hose from the carb to make sure that the air cleaner has no impact? This also allows you to visually confirm that the choke plate is fully open, as well.
Is all the smoke coming out of the exhaust pipe? You mention oil on the carb; this would likely be coming from the valve cover gasket, especially if it is original, as mine was until recently. It means that you're getting good oil flow to the rocker arm assembly anyway, but lighter oil will leak easier.
Have you checked the adjustment of the main jet screw on the carb? If it's a Zenith it is at the front bottom of the carb. It should be 2-3 turns out. I have actually had the jet itself back out with the screw. This creates a lot of black smoke, but the tractor does not run well.
Have you used the tractor enough to determine whether it is actually using much oil? Does the tractor smoke under load as well as at idle?
What about cleaning & gapping your spark plugs (brand & ID number?) and changing the oil again to something like straight 30?
All of this would be easier than replacing valve guides. These old tractors can tolerate a heavier oil in the hot weather.

Does your oil pressure gauge still work? If so, is it reading in the normal operating range?

The heat range on the RJ12C is quite hot. If this was deliberate, the previous owner may have had a problem with plugs fouling. You should ditch those plugs and start with fresh ones, preferably the Autolites or NGK unless Champion are all that you can easily get.

If you do still have the mag on the tractor, it is important that it is in good shape and that you use solid copper plug wires (not carbon centered wires) and that the end connections be clean. This is another common cause of plugs misfiring & fouling up.

Put good plugs in and then pull each wire one at a time with the tractor running. Each pulled wire should drop the engine RPM's a similar amount. If one doesn't have the same effect as the others, trace the ignition system back to the magneto to make sure whether it is bad spark, or not.

Chalmersbob has recommended Champion J11C, which is a hotter plug than J8C, but should be OK if you do not work the tractor hard; for example really making her bark when heavy brush hogging or mutifurrow plowing. I can't find J11C around here, so I use Autolite 295 or NGK B4 as hotter plugs in the winter; but JC8 works for me in the summer.

With a distributor, you should have less problem with weak spark. Check to see that the points are not burned, and that the gap is 0.020". Put new plugs in and then pull each plug wire in turn (wear gloves!) to see that each cylinder is firing evenly. If they are, just run her and check the plugs occasionally to see what they look like.

If you find that the cylinder with the fouled plug is weak with the new plug, you will have to look back to the wire & distributor for any possible problem. The next step would be to check compression and manifold gasket.

But usually it is just fouled plugs and that happens when these old tractors are not out plowing every day.

• Champion Heat Range

Is it worth a try with heavier oil such as straight 30 if not already doing so?