Motorcycle Repair: yamaha yz 125, yamaha yz 125, float valve

Question
i just bought this bike and it makes a rattling noise when running and i believe it is the crank bearings, i just need to know how to tell if it is this or what else it could be. also there is gas leaking from my carburetor

Answer
Vanesa,

-if it makes a knocking noise when you rev it up,
it might be a loose rod bearing.

-If it justs rattles, it is likely the piston
to cylinder clearance is large, the piston
slaps the cylinder walls. It may have a damaged
ring or piston.

-The top end of the engine may need to be rebuilt.
When the top end is off, the crankshaft and rod
can be checked.

-The gas leaking is likely a worn or dirty
float valve needle/seat.
This keeps the carb filled to the right level.

-The float level can be checked as well,
this is the level where the gas sits in the carb.
Sometimes the float valve doesn't shut the gas
off soon enough and the float level has to be
set lower by bending the float where it
touches the valve. When adjusted correctly
it will just fill the carb bowl but not
overflow it.