I've added drag pipes and am now running slightly lean.
I'm not the original owner and am unsure of the current jet size but I do know she is jetted for slip on’s and a mild cam.
I live at sea level and am wondering what size main jet I should use as base line.

Any help is appreciated, Thanks!

 

Take a look at the numbers on the jet, pilot and main. You didn't say if its running lean at off idle, midrange or WFO. Take some plug readings and post the results. Generally if its cold blooded go up a step on the Pilot and depending on the carb fatten the midrange by moving the needle jet clip down a notch. To check the main jet you need a nice stretch of road where you can get it up on the main, give it at least a quarter mile on the main side use the kill switch and kill it. Stop, pull both plugs and see what color ya got. Sould be a nice tan color. Too white fatten it up with a jet two steps up and do it again. two might be too much but most of the time that will get you in the ball park.
BTW the type of carb will make a difference in what needs done but this will get you in the ballpark if its a Mikuni or CV.

 

Thanks for the reply!
She has the stock CV carb with a jet kit in it for slip on's and a k&n filter. I have already been doing plug readings, its lean on the mid and WOT.

 

Does the needle have a notches with a c-clip in it, if so it is an after market needle. Or doese it have a needle with what looks like the head of a nail, if so it is prbably a stock needle. Get the number off of the jets and needle if it is stock, also how many turns out is the idle air bleed and post them then we can do some suggestions. If the needle is stock type then go to your dealer and get a needle out of a 1988 sportster. This will fatten up the mid range and top end. Shimming a needle or moving the clip doesn't affect the mixture until about 3500 RPM as most needles are straight until you get to the very end, then they taper and richen the mixture. Also what are you getting for mileage when the bike is ridden normally (conservatively)??? Hope this helps

 

When I got my 99 FXSTC it already had drag pipes on it. I am guessing the carb had already been modified as the idle mixture screw plug had been removed. I thought it was running a little on the lean side but the plugs looked good although a little on the white side. I added thumb screws to the end of both pipes about 3" in from the end to add some back pressure. This seems to have helped as my pipes are now running darker and low end torque has gone up. Before the thumb screws the pipes were almost white. Did not change the sound at all.

 

ok thanks guys,
miacycles I'll pull the carb apart on sunday to find out whats in there.
Jim Kraft tell me more about these thumb screws.

 

There is a thread on this in Harley Davidson Tech Forums here. Go to engine/fuel/ intake/ exhaust, and then go down to Drag pipe how to. Very interesting. Works for me. I used 1/4" by 1" thumb screws and ended up with the thumb screw part turned straight with the pipe after running it in several different positions. I think a 1/4" bolt about 2 thirds into the pipe would probably work just fine, but the thumb screw does let you change back pressure to whatever you want by turning it different degrees in the pipe.