Serious trouble

In the morning, riding on a Honda Super Cub, never maintanined well, it suddenly went slow down. Before it happened, it runs around sixties or seventies with comfort. After that, maximum speed went down to fourty, then twenty five.
I checked the air intake filter at twenty five thousand kilometers, now it has run over eighty thousand kilometers, without cleaning air filter!
In the afternoon, still away from home, got a plus shaped driver and removed the air filter from carburator. Still it runs up to fourty kilo per hour. OK, pull the choke at some point, then it run well. Easy temporary solution.Yes, later I will cleanse the filter.
By the way, intake sound is so beautiful, not so loud, not so noisy, it's surely comfortable. So I open and close the throttle very often, much more than moto demands.