A chain roller is the go like the modern bikes , new can get after market ones through your local bike shop (all balls etc )
you need to remove the rear shocks,
push the swing arm up so the centre of the front cog ,center swing arm axle and rear axle is in a straight line this is the tightest part of the chain.
then you need to make a bracket for the chain roller if needed and make the chain roller so its just makes contact with the chain.
when the swing arms moves up and down on its stroke it takes up the chain slack.
but you will have to set the chain roller back about 40mm or so from the swing arm axle , so its takes the chain slack well , but you will have to do some dummy runs first. ( for the right spot measurements )
if you set it in the right spot the chain will have the same slack from the tightest spot to the longest spot. ( so when the bike is on its stand there will be 10mm - 15mm or so of slack.
