being able to ride the bike after fixing it for the first time today, it seems that i do have a more sinister problem

still having this whirring sound in gears and alot mor noticable when the bike is gearing down, even get it when coasting with the clutch in so i think its definately transmission related

with this spare motor i have, whats the best thing to do before putting it in? should i just give it a good clean and whack it in? or should i check other things?

i will need to flush and fill the transmission fluid, going to crack open the heads and see if theres rust should i just wipe em off or just leave it there?

its a dry clutch, would i need to clean it to ensure good operation?

anything else? i cant seem to think of anything at this stage, any help appreciated