I wanted to run by you guys what I was planning on doing to my bike before I got it all put back together.  My primary concern is highway performance.  I ride about 30 mile a day on the highway at about 70 mph and I am usually OK unless there is a headwind or I need to accelerate at more than a snails pace.  Then I sometimes end up in uncomfortable situations.  I believe my bike is running a little lean like most, but I don’t get really frequent backfire.  I get consistently 45-50 mpg.  OK, but I wouldn’t mind better.  55-60 and I could put of refueling a whole day.  Is this going to drop even lower while seeking more power or is my bike just poorly tuned right now.

My recent add-ons are a K&N drop in and I am still looking for a Sportster muffler.  Additionally I took out the snorkel and drilled some holes in the airbox door.  I have the carb out right now.  I was going to remove the white spacer but it seems you guys have had better luck just shaving it down.  What is the easiest way to go about that.  I plan on then replacing the main jet with either a 152.5 or 155.  Should I go even bigger?  How do I know the better option, or should I just get both and see which way it runs better.  Last turn the idle mixture screw out about ½ turn.  

I was going to replace the spark plug while I had everything out.  Is there a preferred brand?    

Thanks, love the site.

Sounds like you have the same setup I'm running except for the sporty muffler. I'm using a 152.5 main and am happy with it, either a 152.5 or a 155 main would work. If you are tuning for gas milage use the 152.5 main and install a small windshield, at highway speeds aerodynamics affect gas economy more than anything else. Stay away from WOT when running through the gears, that's the easiest way to drop your mpg. I changed out the white spacer for two #4 washers, about 1/2 the thickness of the orignal spacer. Had to spin them with a drill against a file to reduce the outside diameter to the same as the white spacer. If you are planning to use a sportster muffler you won't need to go much richer than this. Luck on the mods.

All of the above is good.  I would personally suggest using the 152.5 until you change the exhaust, then go to the 155 (and possibly bigger but you'll have to experiment).  I am personally running the K&N drop in though I blew cash needlessly on a rejetting kit that gave me a graduated needle (multiple notches) so I didn't have to shave my spacer.  The net effect is that of a spacer half the thickness of the original.  I have the MAC muffler, the 152.5 jet and the iridium plug.  I can see a big difference in power but will be increasing my jet to a 155 or 157.5 and I'll stick with whichever is the "best fit".

Hey WD

What make is this 45mm carb ?
I have a 41mm Keihin FCR slide carb on my KLX.

Clive W  

Mikuni HSR45. Yeah, it's big, but jetting one of them down is easier for me than adding monster jets to the BS40. To be brutally honest, if I could find an M74 or similar, that's what I'd run. M74 was designed for 61 inch engines, the HSR45 is for 100 inch or larger engines. Even better would be an old Schebler or similar, but I haven't seen one of those worth rebuilding in about 15 years.
-WD

Also went out to my carb box and found a 210 jet, same threads and thread diameter as the original 145 that my Savage had.  It orta fit.

I got it from a local bike shop, when we were tuning my neighbor's Sportster.  They thought it was for an HD Mikuni but they wuz wrong...

You want it, send me your address.

HSR 45

A very good carb but at 45mm is sized more for full race use than road use, a 40 would be better but even then I think you'll come up against that notorius exhaust port restricting power,even more than the standard pipe does.

Clive W