I completed the rib and set the machine for stocking stitch. However when I returned and knitted this it seemed to be taking more rows to get to the armhole! Had I not reset the row counter correctly? The Knitleader sheet certainly appeared to be moving as I knitted each row.
Well as I got to the armhole I noticed the row counter was double the number I expected! This told me that the Knitleader was only moving forward as the carriage moved in one direction.
( This had happened to me previously, so having done a temporary fix I bought a replacement Knitleader from eBay. The Knitleaders are probably 30 years old so is it surprising they are now failing? )
So how I solved this problem - knitting with no yarn was needed. I marked the length of 60 rows (14.7cm) on the Knitleader and knitted 60 rows with no yarn - yes only 7.4cm was actually knitted which confirmed why the sleeve was too long. I added my custom modification to one arm on the Knitleader & repeated knitting the 60 rows, the distance knitted was still 7.4cm.
So, I swapped the modification to the other arm and knitted the 60 rows again and this time I got the full 14.7 cm.
So the immediate problem is solved & as long as I check this modification is not slipping every 20 or so rows it should function.
Longer term I have to decide whether to have the Knitleader professionally mended or just work out shapings from my schematic pattern diagrams.
These vintage knitting machines ( in general) work very well, once the sponge bar is replaced, and they have been thoroughly cleaned and oiled. My experience is that whether it is a Knit radar/contour from a knitmaster ( which tends to get gummed up) or a Brother Knitleader ( in which the triggering mechanism seems to get worn) these devices need more TLC than the actual knitting machine to get functioning well.
So fingers crossed all will work well now and I can finish this jumper for DH.
** The modification works as it provides sufficient extra leverage when the carriage passes to 'trip' the knitleader to register a row.