If it has a BTH twin spark mag then it will definitely be difficult to start no matter what you do on the kick start, this is because their advance curve is the same as for a single spark mag........At any rate using a the AMC gearbox the kick start to engine turn ratio is different, you are best off to get engine up to compression with the kickstart lever pointing to the rear, then using the valve lifter rotate the crank down to the bottom of the kicking stoke, then come up fully and kick it normally. The Mikuni carbs tend to run quite lean, so you may need to richen the idle mixture, either go larger in the jet size or, ream the existing one out with a jet drill if you have one....... I have just been through all of this with a 600 Norvin, changed the BTH mag which failed completely to a Tri spark single output ignition system, this now starts easily and goes like a cut cat.