HarleyTechTalk

Friend just bought a 06 Roadking,4kmi.It's carbed and stock with stage I (a/c & slipons). He's not an aggressive rider.We put on 600mi or so in the past couple of days and his bike only gets just over 35mpg.I ride an 06 FXST Springer with a hot rod 98" build,and ride hard,my mpg was just under 44.Is there that much difference? Or does he need jetting work? Just curious.The other 2 bikes I ride with are 07 FXST's,1 stock 96 and the other a 107 with 255s and their mpg are close to mine.      Coff 06

when he went to stage 1 they probably jetted it too rich. I had a carbed 04 egc mild build and it would do low 40's at normal highway speeds.  Many times they put dynojet kits in when going to stage 1 and they drink gas if not tuned right.

Thanks,Jeffd,that's what I was wondering.He got NO info when he bought it,other than the obvious.     Coff 06

I did a stage 1 on a 2000 SuperGlide with a DynoJet kit. Changed the jets as recommended and gas mileage dropped from aeound 42 mpg to 37 or 38. Then I made it a 95" with SE 204 cams also had some porting done on the heads. I spent some time talking with the smartest tech at the dealer for a while in the middle of the work and tuning. He suggested the stock jets would be fine rather than the richer ones that DynoJet recommended. When it was all done I had him check it out. The dyno run settled in at 13.5/1 so he didn't mess with it any. My mileage went back up to 42 and the bike had a lot more pep.

Check my sig....I'm getting 47 mpg.  Bike is fast.  Ride about 50/50 city/hwy.

Not worried about mine,just wondered why his is so low.     Coff 06
Mine is a 11.0/1 build and runs very well.

Back in 1999, a friend of mine and I rode to Sturgis. My bike was a 1997 Road King, carburetor, and his was a 1996 with FI (a rather unusual bike at the time). We ran a steady 70 to 75 mph, and both bikes were loaded similarly. To make it even better, we're about the same size, so it was a true side by side comparison.

He averaged about 48 mpg, and I averaged slightly less, around 45 to 46.

If I had to guess, sounds like you're friend would benefit from a proper jetting. I would swap out to the stock main jet, stock needle, and probably a 44 idle jet, and see where that takes it.

You can try tuning it on a dyno, but with a carburetor, you're only going to get it so close to optimal. That's the shortcoming of carburetors, you just can't tune them down to individual rpm and load ranges at certain throttle positions. It's okay, you just need to get it closer than it is now. He should be getting in the mid-forties at some reasonable speed.

Most dynojet type kits have you jet it rich for a starting point, and most shops won't go any further than that.

Thanks,Princess Butt,trying to get all the info I can on this as I'll probably be the one to work on it.    Coff 06

His bike isn't jetted correctly.  I often get over 50 MPG with a 95" and mikuni HSR42.  The mileage doesn't come from the main jet.  It comes from properly tuning the pilot jet, idle mixture, and accelerator pump timing and volume.  Have your buddy download the Mikuni tuning manual off their site and read it.