chain and sprockets

I have tried to work out from elsewhere on the forum replacement chain sizes, I have read that a 520 will fit the commando, mine is 1976 850 mk3 elec start. I would like to fit a DID x ring chain as I use these on my enduro bike and they are really good. is this over kill, the problem I am having is The Pitch, will this fit standard sprockets, mine are not hooked so I was not going to renew them. I know you are recommended new chain and sprockets together. so help and suggestions really required as I am going on a long mountain tour soon so would like to get sorted. what chain fits what sprockets? 520 525 530etc thanks Neil

Stock sprockets require a 530 chain. Just put an EK x-ring chain on mine. Stock sprockets can be obtained from a number of Norton parts suppliers. There are clearance issues with an o- or x-ring chain on older models (750) but the 850s have plenty of room between the gearbox and back of the primary case.

530 chain is 5/8"x3/8" (5/8" is the pitch) which is correct for Commando sprockets. 525 is 5/8x5/16" which requires the sprockets to be machined on width. 520 is 5/8"x1/4". If you choose this size you can use pre 1965 Dominator gearbox sprockets, but would still need to thin the rear unless your bike is an earlier model without the cushdrive. In this case a Domi rear should fit.

Some like me can fit wider sealed 530 chain directly but d/t Commando clearance variations some found this extra wide chain makes noise for a few miles as it chewed a non structural groove out bottom to AMC shell then smooth sailing. To simpliy 520 convertion an Atlas drive sprocket is direct slip on then just mill drum teeth outter sides down to .240" removing some the hard wear surface but plenty of time to keep eye out for next drum to convert. I think I could tell benefit of 520 topping Peel out in 1st 2nd lifting front a bit sooner and similar on my SV650 but so rarely got to appreciate that slight delight and fanning over drive teeth & turning rear teeth into non working rounded nubbins twice decided to forgo any more hot roding on 520 but still leaves 525 chain like my SuVee came with.

thanks everybody, will get on with the job now