I have an `04 FLHTC that coughs and spits just off idle.
I plan to change the needle jet to an `88 sporty jet and bump
the slow(pilot jet) up one size. Can some one tell me what size
slow jet comes in the carb from the factory?

Thanks..................

 

Not sure but likely a 42 or 45
when you say 88 Sporty jet did you mean the needle ? as in the N65C

 

It should be a 45 and you do not need to change it unless you put cams in or changed the C/R. Jus adjust the air bleed out two turns to start and when it is warmed up readjust it to where it idles the best. Hope this helps.