Trying to get the wifes little 250 running in top shape for sale, its having throttle issues.
Its been ridden every week but just around the neighborhood to keep oil on parts, never tried to open it up top speed till this past weekend.
Dang thing is bogging mid throttle, happened once or twice on the wife couple  months back but I couldn't get it to reproduce the problem, ....until this past weekend.
I've checked the petcock flow (clean and fast), the carb bowl (clean and fast), I am looking dumbfounded at a rubber tube that runs across the top of the carb and ends under tank...cut off at a 45% angle, i'm thinking it is supposed to be a crank vac since it goes all the way to the bottom back of the engine and I can't see it going into the case ( I plugged it just for kicks)
After removing the air box cover, the air filter, and plugging the unknown tube, dang thing runs better! filter smells kinda fuel soaked but is dry, and has a vac tube attached to it.
Well anyway with everything attached stock it won't accelerate very well at all, matter of fact I could outrun it with my busted back! but when I plug the mysterious line and remove air filter and cover it will go up to 76mph! and fairly quickly with minimal mid range bog.
Thanks fer helpin' or hagglin' ....i'm just lost and throwin' it all out there.

OldRider

That tube wouldn't be the vent for the top of the carb bowl  would it ?  It probley should go to the breather box instead of venting to the outside .    As in ; "let air out , so gas can come in" ?
Just guessing ...

I just sold my Suzuki GN125 to a young feller for his first street bike ... he'll be ready for a bigger machine shortly.     You ready to pay somebody to take that "truble making machine" off your hands yet !