I have the HPD pipe on my 500 scram and a K&N filter so I put the 160 mainjet in like HPD stated I should and turned the air fuel screw out 3 turns from lightly seated when Idleing everything seems fine but give it a few shoots of the throttle and you can smell the raw fuel should I drop down to my stock size mainjet a 155
I should not get a lean problem with doing this do ya think were this is a 4 stroke andthey are more tolerate to jetting right ???????????

 

A 160 sounds about right for your setup. If I'm not mistaken there is a 157.5 main available for the 40mm carb. You might want to try that before going back to the stock 155.