New TW200 owner, need help!

Hi team,



I recently bought a glorious import TW200 (been looking for years!) and I was wondering whether you could offer some advice on a few things.



The electric start has ceased to work, it just clicks as if there is not enough power. I know that the battery was replaced to a larger size just before I collected it. I thought that after riding it consistently for a few days that it may charge it, but it still gives 1-2 turns then click, click, click.



The air filter has started to corrode (see attached photos). What is the BEST air filter for a TW200? and what is the normal SIZE I would be after?



Also, what is the red button for next to the choke pin?



Am I able to clean the air filter to get this white, corrosion like dust off it?



Thanks guys, I have attached links to the pictures below because I wasnt sure if the pictures would display within the forum post.



Happy riding team, stay upright!







one of the hoses connecting my air filter pod







Old air filter I want to change out







To find the correct air filter size, do I measure the carby at this point?







What is this red pin/button for?







What would be causing this white dust/corrosion on my pod filter? Can it be cleaned off?