Inconsistent tension- knots visible alternate top/bottom

[Gregg From Keystone Sewing]

Are you winding your own metal bobbins, or are you using a pre wound bobbin?  I've seen some pre wound bobbins that were so inconsistent that they would do this.  Wind a metal bobbin and see how it goes, if that's the case.

[Yetibelle]

Since I always forget I have this chart - Yours looks nice really, It can get much worse that that.  Sometimes I find a new needle helps, also let the machine pull the work.  It's very tempting to help it along as you guide it, that's when I find I miss a stitch or bend/break a needle. 

 

 

 

[Singermania]

I agree with the guys, the needle is too big, you've massive hole there.   A  140/22 should be heaps big enough.