What motor oil does the 1979 Husqvarna 390 OR, take?

what weight oil are you using , I have found that the new saws work best with a thinner oil , the old(r) guys work even with straight motor oil ,but the newer ones have to use 20 -30w bar chain oil

a dab of kerosene can be added to filtered used motor oil to make a very fine chain oil for less cost

There are two different units used on there garden tractors, Hydro gear which uses a sae 20-50 motor oil, or a Tuff Torq unit that uses a sae 10-40 motor oil, they do not use hydraulic oil.

Hydro gear box takes a sae 20w 50 motor oil, Tuff Torq takes a sae 10w 30 motor oil

try a fresh batch of fuel mix

Remove the motor mount bolts and raise the engine slowly. Don't dent the oil pan when raising the engine! After the engine is raised, you should have enough clearance to remove the pan.

Personally, I use H-D oil for the engine and tranny. I use 60wt engine oil and the H-D semi-synthetic transmission oil. Now, there are many other brands of oil that you can use. Golden Spectro, Royal Purple, RevTech, Amsoil, Mobil, Motor Factory, and many others. You need to go to their websites to find out what is recommended. H-D oil is close to me and priced about the same as the others.

Good Luck
Steve

lift hood you will specks usually under hood or around in that area I usually use a good brand 30w oil

It is a 2 stroke motor there is no oil you put in the motor only 2 stroke oil in the tank so it will mix with the gas.

the ford fe motor 390 heads should be torque to 90 foot pounds

are you sure the tranny is not leaking gear oil?