Early 1952 J.D. G model- runs very rough, vibrates. runs good on pull, vibrates. Tried good different carb and dist. This tractor apparently was built of many other tractors. The flywheel was out of t

Check the spark if it has a module it could be getting hot,check coil and leads.

i would suspect a carb issue first

Just a thought,pull the dist.cap and make sure the rotor has
no side to side play ,thinking maybe a bad upper bushing in
the dist.Also,if the EGR valve has carbon and soot built up
on the piston it will make it idle really poor ,but run ok.
Might pull the EGR and clean it with intake cleaner.
Hope this helps.

87 has no ECU. so must be an engine swap to a 89 or newer tracker
or last sammi that did have EFI.
you said EFI and Carb in same paragraph and that is a contradiction.
post to my bbs for more help.
http://www.fixkick.com/bbs/

post a link to a photo of your engine, many sammy cars have a newer engine and EFI added. no matter we can fix it, but you need to learn whats under the hood first, photos rule in this word.

your truck is running too rich with fuel if you have a carburator have it check

Have you checked fuel pressure?
Vac leaks ?
Restriction in the air intake ? Faulty EGR valve ?

have the intake gasket checked. spray carb/choke cleaner around intake gasket and if rpms change then you have a bad gasket which causes rough idle bad fuel econ

It would appear that the Black smoke is unburnt fuel, meaning Spark or timing could also be out. Check you plug and point gaps. If you rebuilt the carby, float level is crucial also check the needle and set to ensure it is shutting off the fuel, if it is not shutting off, it will just flood the engine. Not sure what carby you have but I woud pull out the jets/power valve and replace them. Some carbys have a small ball bearing to control fuel, if that was lost that could be it. Pull up an exploded diagram of the carby and do it again. I know its time consuming, but it will be peace of mind. Good luck

check your timing. might be to far retarded