Installed HD 09 FXD Calif muffler ( sounds great )  Installed K&N air filter. Left air box door off. Adjusted air screw. Had to come out 3 1/2 turns to get smooth idle. Additional turns out had no effect. Eliminated most of the after fire. Bike ran smooth before replacing OEM air filter but had excessive after fire. Have tried to find the next larger air screw or pilot jet but can't find anything but rebuild sets of original size.   Can you change the pilot jet without removing the carburetor? Bike seems to run a little smoother after 4 or 5 miles when it is really heated up but still has noticeable loping. Our one good honest repair shop is closing and my only other option is Rideout the Suzuki dealer and they are very expensive. I bought my first motorcycle four months ago at 86 years old and have put 550 miles on a 2016 s40 that only had 381 miles when I bought it. Any advice, expert help or guidance would be greatly appreciated. I live at sea level 25 miles south of Jacksonville Fla.

I am one of the guys that differs in jet sizes....maybe the fuel in the US is different than BC.

This area has riding between 500 - 800 msl.  My "go to" jetting has been the #50 pilot and #150 main, and three #4 machine screw washers instead of the white spacer on the slide needle.

Each bike can be a bit different, and my personal bike still had a lean surge at low throttle settings.  Changing the pilot jet to a #52 didn't help, the smoothest jetting was obtained by removing one of the washers from the slide needle and using 2 washers (#50 pilot #150 main).

I just did a bike that had sat for 2 years and it needed a complete fuel system cleaning.  I tried drinking the "cool aid" and I installed a #52.5 pilot jet.....along with the #150 main.  When I tried adjusting the fuel mixture I could turn the screw all the way in and the bike was still running rich!  I put the stock #47.5 pilot jet back in and the bike ran great (#47.5 pilot, #150 main, 3 washers on needle).

Each bike is just a bit different.  You want the pilot jet sized so that the when the screw is adjusted for the smoothest idle - the screw is around 1.5 - 2 turns out (at a very low idle speed for adjustment).  If you need to turn the screw in farther the jet is too big......if you need to turn the screw out farther the jet is too small.

I am starting to believe that the pilot jet has very little to do with how the bike runs - as most riding is done with the throttle open and the needle or main jet have the most affect.  The pilot jet does affect how the bike runs when the throttle is closed.  I do believe that installing a larger pilot jet can reduce the backfires and afterfire - at the expense of a bit of fuel MPG.

Start with 3 washers on the needle.  If you have a lean surge at low throttle settings.....remove a washer and the lean surge should go away.  Don't worry if there is a little bit of a surge when the bike is first started and has not fully warmed up yet - that is a sign that the mixture is good and not overly rich.

And a #150 main has always been adequate for this area.....sea level may prefer a #152.5.....mountains may require smaller.

All my jetting has been done with the stock paper air filter.  If you install different filter you may need to go up on the main jet.....I don't believe that there is much of an affect on the pilot jet as there is so little air moving through the filter at idle speeds.

When you adjust the idle mixture you want the bike fully warmed up.  You need to go on a 10 -20 minute ride before making the final adjustment.  Turn the idle speed down to around 800 rpm, then quickly adjust the mixture screw for the smoothest idle.  Then turn the idle speed back up to 1,100 rpm.  I do this while setting on the bike and holding it upright - allowing the bike to idle on the side stand starves the exhaust rocker for oil.  As noted earlier - if you can turn the screw all the way in and the bike still idles....the pilot jet is too big.

Just one mans opinion.....your mileage may vary!

   

I did the 50/150 for a year and always felt the bike had more to offer. Without measurements (fuel/air) the 'seat of the pants' tells me 52.5/152.5 is my answer. I may be a bit rich, but ride 'feel' is terrific, on 87 octane. The bike I sold last year had the same jets, same effect. Both with 'white spacer mod', dyna muff . Before my tach broke I set the idle at 1300/1400.
The bike just 'gets up and goes'!
Cheers!  
ps: also K&N RC1250 cone filter !

My 2 cents:

I recently returned to riding and found a pretty good bike. It's supposed to be "fully stock" but it does have a Dyna muffler. Still had to OEM rubber tho.

On a good day, it surged pretty badly. Turned out to be the petcock. Added a K&N, then tried the airbox door off. No good without re-jetting and backfired like mad. Reinstalled the door, tuned the idle mix, and enjoyed 2100 miles+ over the rest of the summer.

My best advice is run pure gas first, then tune. Hands down.

Since re-installing the door, I've read a few articles about similar airbox mods to increase flow which are actually counterproductive as they interfere with proper A/F mixing.

My backfires aren't excessive, the bike pulls well, is a blast to ride, no surging, and I easily get 60+ MPG.

Welcome to the fold!

I know this is off topic, but, OHIOMOTO I sent you a PM about a week ago.  Please check your messages.  Thank you very much!!!  wiguzziman

Number two Phillips is not what fits the bike.
You can grind the tip and set it on down into the bolt.
Or buy JIS screwdrivers.