The hole in the case is 18 mm. The part , which I bought and used is 20 mm in dia. I can find no sources of the 18 mm dia condensors.
The work around is to file the hole larger and slice the yellow wire to the magenta wire from the old condensor to make a long enough wire to connect to the wiring block.
see email I just sent and picture.
FYI Mike Cornell was very helpful and initially offered a refund and return.
I sent him back the refund and used the part, seen in the picture.
That part by the way is new aftermarket and sold by many sellors for Vespa 6 v scooters, on ebay for instance 12 - 15 dollars?
Mr. Cornell, fyi for future information, on the 544 , which actually appears to be the after market condensor for the 6 v old vespa SCOOTERS. , I easily expanded the hole in the case to accept the 20 mm dia., with a round file in 4 minutes. It does make some
Aluminium filings which must be removed. The screw hole even lines up, but the fit is snug enough not to need it.
There is no source of new 18 mm dia condensors I could find.
I will paypal you back the money since I will keep the item and let you know if it
Solves my spark issues. (edited)