i decided to take the bike out yesterday, it was about 45 deg. outside. i noticed the bike acted much leaner even after a 20-30min ride on the highway and back roads, even got a couple of carb farts cruising at 60 mph. the bike has always ran smooth during the warmer temps is this the norm or do i need to adj. the carb?

carb has 45/180 jets 1.5 turns out on mixture plug, bike is stock sept for slipons.

what do you think?

 

Sounds lean alright, you might change the needle for the '88 sportster version?

 

I would turn the mixture screw out to a full 2 1/2 turns. Maybe 3 if it still popped in the cold air.

 

Try turning the screw first but the Sportser needle is a addition to a stock CV carb.

 

ok will do thanks for all your help.

 

A 46 low jet may make the difference in your case. The mixture screw should always be adjusted with the bike fully warmed up and to obtain the highest and steadiest engine idle and not a pre determined amount of turns open. The size of the low jet will determine how many turns open the screw will be for optimum performance. The larger the jet to a degree, the less turns open the mixture screw will be. With the proper jetting the mixture screw will be open about 2 1/2 turns from lightly seated. All the jetting and adjustments should be the proper size for a smooth fuel transition throughout the entire range.
If your slide vacuum port is drilled it could be giving you a drivability problem from the slide opening too fast and causing a momentary lean condition which would result in a pop back.

 

funny thing is that the bike came with a 185 main, which i thought was too rich.

it would just smell rich and it would start up with no choke, now it seems like maybe the p.o. had a reason for the 185 main jet. the original plugs were a nice chocolate color so now im thinking it was a mistake to goto a 180 main.

 

Here's a quick and easy way of testing the main jet size.

Run the bike through the gears into third gear and run third up to 60-70 MPH full throttle, then chop the throttle about 1/8 to 1/4 back and see if the bike either surges ahead or stumbles then recovers.

If it surges ahead, your jetting is lean.
If it stumbles and recovers , your jetting is rich.
If it makes no difference, you're pretty close

It should tell you something about the main jet size.

 

ya i did that already. at high speed its smooth, it just suprised me the other day in the cold 45 deg i got a couple of carb farts at 60 mph. 75 and 80 mph was fine. i think its just the cold air leaning the carb out. the bike ran just fine at 55 deg and higher.

 

It could also be the transition between the circuits doing it too.

Have you tried to raise the needle with 2-#4 washers which brings in the fuel a bit sooner.