Hi, I had low compression on my 73 750 and it would not start properly, 55psi & 95 psi which is far too low.
The bore could have been worn, so on the recomendation of the guys at RGM motors in UK I put a set of Cord (or is it Chord, I cant remember).
You put 2 thin rings in each grove & they are sprung steel & not cast as usual rings. They give you better compression if your bores are a bit worn, but I belive they wear the bores quicker than conventional rings.
Mine has now got good compression & start 1st or 2nd kick.
They are a real bugger to fit in the barrels even with ring clamps so I had to put the pistons in the bores on the bench then fit the barrels afterwards & fit the pistons to the con rods while my mate held the barrels in place, this worked on our 2nd attempt.
Maybe the bores will wear a bit quicker but I dont do that many miles each year.
Maybe not the best rings but it was a cheap fix for me (lets face it I do live in yorkshire), & it now works perfectly without burning oil & I cant stand on the kickstart for a while before it goes down.
Best of luck
Cheers Don