Fantasia Automatic 968 has now got top stitches with bird nest. I also cleaned out bobbins and oiled it. Further, I changed my needles and have changed the thread too. I am dreaming up about its tension.

I acknowledged anyone's opinion regarding this matter.  

It's appearing like old version of embroidery and I am bored with its name. I even had never heard of it. I tried to call local singer but they are not able to help me. 

Pop! It is quite old and made up metal and interestingly knobs are made of plastic. It is only having foot control and does not have on or off switch.  I would say, annoyingly, back to the age of industrialization. 

Just go through this website for manual help. It's free http://www.singerco.com/uploads/down...9b2969d86c.pdf

Thank you very much for your help

This is the issue probably associated with the bobbin. You should always make sure that the bobbin is going through the tension from left to right.  You just need to tight the screw of the bobbing housing via turn method. Old machines have stuff like 'U'. And, please carefully look that threading is passing through this U or not.  If you did not see, you have to look carefully it may have broken. 

I basically love in working with those old-fashioned machines. I am always ready to help and I would have been even overwhelmed if I was there to help you. My mom is also very much interested in this old type and she got kenmore from a shop on $20. Initially, it has stitching problem. But, after cleaning it is ok now. 

Upper tension guides are available in the singer dealer shop. I have to look on my Bill for buying this machine. Really, this machine drags me in the memory of 30 years ago but I am not mocking. I am using 35 years old machine and owning more than 20 years. It really had repair shop. I saw the one last year. 

You should figure out the piece of broken plastic and go for replacement. You probably get awesome machine after it. 

Hurray! You got the problem. I have old Singer but it is too loudly and I should take care while using it. I have to make sure that, my husband won't be disturbed.  My husband wants to buy new one for me but I love this creature. 

Great! Great! You got the problem