LOL :thumbup::thumbup::thumbup:

Yes, threads changed, top and bottom (and always the same for top as bottom), needle bar shaft clean and oiled, tension assembly pulled apart and checked...all clean and hunky dory there....I put a spot of texta colour on my thread at the base of the thread guide before it goes through the final guide just above the eye of the needle. When I have sewn the black stuff starts before the texta marked point gets to be sewn so the problem isn't "upstairs" methinks....must be happening somewhere under the needle plate but blowed if I can figure it. Shuttle and cradle are clean, needle groove under the plate is clean.......and it's now 2.00am and I'm giving up. I've also got uneven and missed stitches appearing on the underside as well just to make me even more delighted...and once again, only when I am treadling, not when I am hand turning! Might just check that my needle is in correctly before I turn in for the night....errrr morning! sigh.

I've been fighting with a 401 with tension problems. I even took the tension off that machine and put a different one one. I pulled out the bobbin holder and replaced it - I'm thinking there might be some other adjustment. It will be in the last place you look. LOL

I suggest just sewing scrap material with cotton thread and it will eventually clear itself. perhaps spraying some of the thread with alcohol.

Love it! hahaha Gave me a good chuckle! :D

So I have managed to find a speed with the treadle where all goes well. I have marked the needle thread with texta at all my thread guide points and have found that the black marking starts before the texta marks start to come through with my stitches. This means it's happening at the needle and bobbin area, not before. Now, could this be as simple as my treadling so fast as to make my thread spool unsteady and foul the thread delivery for a second or two during which time the needle and stitch formation is stressed and momentarily "jamming/fouling"? Then, after a second or two, the thread is released and normal thread pay out from the spool continues? Is this feasible? If so, how can I secure my spool better or should I just compromise and treadle at my nice sedate "nana pace?". Any advice happily gobbled up. Have attached a photo of the cushion cover I was working on......a cushion cover made for my granddaughter on her great great grandma's treadle WITH old lace found in the cabinet drawers....feeling all warm and fuzzy inside!

I was going to suggest switching to your 99k but you just explained why not. I'd love to have a look at your machine but I suspect you live nowhere near Northcote. BTW lovely cushion cover: Looks very nana :thumbup:
Now, there *must* be oil somewhere along that path. I'd treadle normally for a bit and inspect the thread to see where the blackness starts. Alternatively you could just wipe it all with a white cotton cloth.

Shame I am not closer to Northcote Mike...I'm out at Lilydale...other side of town but thanks, I appreciate the sentiment and yes, I agree, something is amiss, somewhere! At least for the moment I have found a compromise and have been able to finish the cover. I'm sure I am probly missing something screamingly obvious :o so will keep puddling with it over the next few weeks giving it a good run as often as I can to see if that eventually "rubs off" the problem.
The blackness happens randomly, sometimes immediately on starting sewing, sometimes not for a few inches, sometimes lasting only a few stitches, and sometimes lasting for as long as 1/2" or so.

Thankyou everyone for all your suggestions....

This is what I would do. I would take some scape material and just keep sewing till your thread come out clean.

Excess oil is spraying from somewhere. I had oiled my 1941 and noticed spots on the scrap fabric when sewing at speed. It was coming from inside onto the take up arm. I took the faceplate off and wiped the parts, problem solved.

Alright then...took the janome in for a service today and spoke to the tech about the treadle. He reckons the timing needs adjusting. Ooooo, haven't done that before......should I let the tech do it for about $120.00 or is it something I can do? I'd rather do it myself but what does it involve...have had a quick scoot about the net tonight and not found anything specific to a 127 so am none the wiser but am really keen to learn. Will have another look on the net tomorrow....eyes are weary but any advice as always gratefully gobbled up.