New Juki 1342 problem - breaking thread!? Plz help

[RasberryD]

hi all, got myself a new juki 1342 cylinder arm machine. When i tried it in store it all worked well, when the engineer brought it home, it all worked well. An you guessed it the min i'm on my own the dam stupid ***************! thing doesnt want to work. It keeps breaking the thread (135/138 or 20) bonded nylon, it is heavy thread! and i'm getting birds nests underneath. I have some experience, but mostly a newbie to industrial machines. I have a suspicion there's an "issue" with the bobbin thread loosening up / overwinding on the bobbin. Anyway i'm attaching pics for u to see. The birds nest on the red rubber is me trying to sew from the wrong side. I do have a video but the site wont upload it because of the size. I'm so pissed off and sad right now i dnt know if i shud cry or break something uuuuuuh!

[twotrees]

Firstly, recheck your thread path, this is often the cause of the majority of sewing problems.

Thread breakage often occurs when the needle is too small for the thread - try using a large needle or a smaller thread.

Bird's nests on the underside are often a sign of a lack of top tension, try increasing the top tension half a turn at a time.

Try to keep your bobbin filled to a maximum of about 3/4 full, and check your bobbin winding tension too.  Also worth worth checking bobbin tension - if you've made a drastic change to the thread size on your bobbin you may need to adjust the spring tension down there too.