i've been long-arm quilting for 10 years now- and can not use YLI quilting threads either- it's not your machine- its the thread-
i've been very upset in the past to go to a show- spend $18+ on a cone of thread only to bring it home and find i can not use it for quilting-
but it happens.
try to find quilting threads that are 50-60 wt threads- they do not have to say quilting thread to be used- i use alot of different threads for quilting- just not yli threads-
i've had very good luck with the machine quilting threads from Connecting Threads- and also Superior threads *superior threads have wonderful free thread/needle charts that will help you choose the correct needle/thread combination for any project- a very good resource* i buy thread by wt/fiber content- not by company name
in my long-arm trying to use cotton thread is usually my nightmare-
and when choosing by weight- the higher the number the finer the thread---12 wt thread is like a string- very heavy/course---50 wt thread is quite fine---silk thread is often 60-100 wt.
the reason the numbers are how they are-is based on how many miles of thread it takes to get a pound---if it takes 20 miles of thread to = a pound--that is 20 wt thread---if it takes 40 miles to = a pound that is 40wt thread....ect.