lost gas

[ramo]

A couple of months ago i could get about 200 miles on about three and a half gallons of gas. Right when winter hit and took it to a dealer ship to get an oil change it  got 88 miles on three and a half gallons. After i did my first oil change to it, it now gets 96 to 100 miles on three and a half gallons. whats wrong and what should i do? this is my first motorcycle and i would like to do the work myself, i dont trust dealerships now.

[Jasco]

Does it smell like gas?

Is it leaking gas?

How does it run, idle?

We need more info to diagnose the problem.  Hard to do over the internet anyway.

My thoughts are:

running to rich, but running that rich I don't think it would run.
Gas leak
Carb issues

[ramo]

after riding it  sometimes it does smell like theres oil burning could be gas, but no leakage, it runs smooth, accelerates well.