Replace the jet needle and the needle jet . it is the one in the center of the carb .the hole in jet gets enlarged by all this crap gas they are forcing on us WHEN THE NEEDLE COMES DOWN IT IS SUPPOSED TO CUT OFF THE FUEL FLOW ,WITH A WORN JET IT ALLOWS TOO MUCH FUEL TO BYPASS THE NEEDLE FOWLING THE SPARKPLUGS .
Adjusted too close to the floor.
Are they drum? If so they need to be cleaned and adjusted. Ensure there are no leaks.
My sons did the same thing until I cleaned the carb out and adjusted it properly.
That this used phone has been repaired, adjusted and cleaned to look and work as new but is not a new phone.
The fuel filter is clogged or the carburetor needs to be cleaned and/or adjusted.
Keep all the parts of the drivetrain properly cleaned, lubed and adjusted.
first thing to do is check the spark plug. if its fouled, clean it or get a new one.
Possibly fix the vaccuum leak !!
If the carburetor is cleaned on the Yamaha Bruin 350 and it will idle but stall when given gas, it could be that the float is sticking. The carburetor may also need to be adjusted by turning the adjustment screw so that it is not getting too much gas when revved.
Sounds like the previous owner did not do the required maintenance, it sounds reasonable to me.
If you are having a low pedal feel, chances are you do not to bleed you brakes. I beleave you have shoe and drum set up in the rear. Have your brakes cleaned & adjusted. This will firm up your brake pedal.
You should never need to replace a carb. Cleaned yes, rebuilt yes, but not replaced. If the car is being driven then at most you need to have it adjusted and tuned up. The only time you will ever need to replace a carb is when it is so gummed up from sitting that it can't be cleaned properly.