D15 - diagnosing engine smoke

So had the D15 (series II) out a few times the past week....raking and tedding hay.

So as usual, one bump of the starter and she starts and runs. A bit of black smoke but moments later, seems to clear up. From my perspective when sitting on the seat while running, I seldom see or notice any visible smoke. At least nothing excessive. But......neighbor was running her the other day....tedder and later rake, and from a distance, as she passed a treeline with dark background, I could notice a plume of dark colored smoke.....and now and then a hint of blue.

On the blue smoke, she does not seem to use a lot of oil. After 10 hours, she may be a half quart low.

She does seem to use a lot of gas. About 1/4 tank per hour.....and that is at no more than half throttle under a light load.

Source of the smoke? My guesses are......

Rings for the blue smoke and if there is any blow by......which there may be.

Carb adjustment for the dark smoke.....too rich?

Corroded valves?

Valve lash?

So what are the causes and what are the remedies?

Well if the main jet adjustment process works doing it your way (knowing the source, I know it is), it is doable. The shop manual version was going to be a problem. Wrote that after you had posted before.....without seeing your first post.

I try to operate under the premise of "first do no harm"......don't break something that isn't. But sounds like this is something that can be tinkered with and not do lasting harm.

Good learning opportunity.

A D15 with a healthy engine and properly set carb will not emit any visible smoke when working hard.  With that amount of oil consumption, I think you've got problems.

In response to a thread a while back that I seem to recall asking for resolution to problems posed.......here goes:

Tractor was put on a dyno to see what the smoke problem might be, and a knocking noise was detected. That pretty much ended the test, and source of the pops and sputtering engine never discovered. We decided to pull the engine for an overhaul.

What we discovered was one of the clips holding the wrist pin in #1 cylinder had fell out at some point. Clip would have been captured inside the cavity of the piston, but was free to pound around until it was eaten into metalic dust......and scored the sleeve in the process. If memory serves, with clip missing wrist pin was free to float and was doing damage on the other side.  Found deep grooves cut in the sleeve that would have allowed oil to bypass rings and was probably the source of the blue oil. Compression on that piston about 115. Others were closer to 150. So that was also the likely source of the blow by I was seeing.

Rod bearing on #1 cylinder was badly worn and about to let go.

All other bearings and seals worn but still OK. Valve guides and valves worn but were not yet causing problems.

But put in a rebuild kit from Reliance.

So.....new pistons, sleeves, rings and wrist pins and cam and crankshaft bearings.  Rods OK. Valve guides replaced. Valves ground and seats lapped. Crankshaft and cams ground. Reliance Kit was complete except for rod bearings, and when we finally found those, crankshaft had to be ground a 2nd time for the different size rod bearings. (If memory serves, went from 10 thou to 20 thou under as that was all we could find).

Put a rebuild kit in the oil pump, which upped oil pressure on the gauge about 2X. Didn't look worn, but apparently was.

Head gasket supplied by Reliance failed out of the gate. Wouldn't hold coolant at all.  Found a replacement Victor (NOS) that worked well.

Took opportunity to have radiator checked and wound up replacing the core. Also needed new radiator cap.

Installed new plugs (Autolite 303......US made NOS), Blue Point points and condenser.

Made switch to 10w-30 oil for diesel engines.

Put her all back together and she fired right up! Had a few minor oil leaks around governor lines and seals, but otherwise all good, including the front crankshaft seal, which is a bear to get back on. Shop manual calls for a special install tool that doesn't exist, so I wound up making my own.

Parts alone for the rebuild probably exceeded value of the tractor and with hired labor to help, far exceeds value of tractor. Probably not a good financial decision, but she runs like a top now. Used her again for raking and tedding and engine sounds different and responds different to a load. Hard to describe but you guys familiar with the sound of that engine will know what I'm talking about.

She has gone from something on her last legs and life support to workhorse.

PaulB wrote: Tractors, unlike cars (with automatic chokes) Need to warm up before using when the carb is properly set. When your D15 was using too much gas it would start and take right off. Now it needs to be warmed up.  No big deal use it as it's intended

That is exactly how she is now. Needs to warm up a bit or will stall out. Good to know.