My girlfriend's '81 GL500 Silverwing is bogging down at idle in neutral and dying in first gear due to low idle speed. Very new to motorcycles but thinking this has to be some kind of fuel issue. Is this a carb issue or does it have something do to with the what I believe is an aftermarket fuel filter or something I should check in the tank? Thanks in advance. Getting my '82 GL500 Silverwing Interstate later this week!