I have a 1948 D6 9U serial#:2087 that I purchased in January. I've never owned a dozer before, but have always wanted one and now have 3 (I'm really making up for all the years of not having one and lost time lol). I've never been around or worked on one until now and it's definitely been a learning experience as it's different than working on tractors.

I haven't gotten to push the first tree or pile of dirt with it because it's been very neglected over its life and it's very sad, so I've spent the past 10 months working on getting back up to snuff (you wouldn't believe some of the shade tree patches I've uncovered ie: a homemade rocker arm under the valve cover lol).

My question is this: it's always had a spur rat tic pop/miss and smokes like a freight train (don't have to worry about skeeters or much other insect life the smoke is so bad 😅😂) and slobbers out the exhaust since the day I went and looked at it. I changed fuel filters, injectors, air filter, both thermostats, and all the other maintenance. It doesn't seem to have bad blow by out the oil filler hole, it has great fuel pressure, starts up very easily with electric starter, and pegs the oil pressure needle. What is wrong with this thing? I'm at my witts end and I would like to use it 😅.

Any help would be greatly appreciated.

Put the tractor to work The slobbering sounds like the cylinders are glazed. A couple of good hours working the tractor hard might clear up the problem.
Chuck C.

Even with the popping? I don't really have anything I can do with it at the moment as the CCU and blade are off it currently for repair.

Is it possible that it has a broke ring(s)?

Hi Team,
as said above work the machine hard for a few hours---the popping is due to oil that has passed up past the piston rings due to the bores being glazed from light work and/or idling.
I was once told that over time as the oil builds up and some of it gets hot enough to burn off in the exhaust and that is the pop you hear.
Many engines have cleaned up after some work.
In the 1960's at The Dealer we used to get a D17000 in every Christmas Break for slobbering, just as your engine is, as this engine was not laden enough running a face shovel at a local quarry.

This is usually the first step in a process of elimination. See how it goes and report back.
Back in the 1960" we used to put stickers on the dash of new machines with words to the effect of :- WORK IT DON"T BABY IT due to slobbering issues of people lightly running in new machines--Diesels of the day need to be worked to stay clean.

Cheers,
Eddie B.

agree with all the above...work it hard to create some heat....

you didn't say if you checked or adjusted valve lash....that can point to some other possible problems within valvetrain etc...if the popping doesn't clear up or lessen...

Bad valve guides and seats will make it pop and smoke too. You said it was very neglected, most likely needs overhauled if the hours are high.

Thank you for all the help!

Rome, it cranks over easy and fires right up with little blow by (or atleast in my opinion its little) and it pegs the needle on the oil pressure gauge; could I get by with just rebuilding the head?

It also seems like it's getting air in the injector lines, but I haven't done much in depth work on the injector pump/govenor, how would it be getting air in the #2 and #4 injector lines?

my ancient but beautiful d6 4r behaves similarly so all the posts are timely for me. I've been babying her.
just out of curiosity, when you say yours has electric start, is that direct electric or pony electric?
also I just noticed that the new website no longer identifies the location of posters in the post (this one is in Montana).