I ride a bantam that has a 428 chain fitted and have a cub with a 420 fitted. Whilst riding these in trials i have had people comment on 'you don't need a 428 they run better with a 420 and vice versa when running the cub with 420. I only use these sizes as that is what the bike come with.

I am now replacing the Bantam chain and sprockets, is there a noticeable difference n performance or chain/ sprocket life between 420 and 428?

I ride a bantam that has a 428 chain fitted and have a cub with a 420 fitted. Whilst riding these in trials i have had people comment on 'you don't need a 428 they run better with a 420 and vice versa when running the cub with 420. I only use these sizes as that is what the bike come with.

I am now replacing the Bantam chain and sprockets, is there a noticeable difference n performance or chain/ sprocket life between 420 and 428?

I have no experience of 420, but run 428 on my B40. I replace the chain regularly and have found the sprockets last really well. Some people run 520 on B40's, but no one has ever said there was any advantage to me. The only thing to be carefull of is heavy duty chains fouling the engine cases.

and that literally is the rub, my cub came originally with 520 its previous owner was famous for his wide chains. the chain wear / lifespan has been no different when changing down a size or two in the 5 years ive had the bike ive done over 150 trials and i'm only on my 3rd chain so its a non issue .. except for the engine case 'rub' which is too big a risk to take..