low mpg

[speedlimit85]

been getting 31-34 instead of 36-39

just changed air filter and there is a wee bit of gas in there

is that okay?

[Radioguylogs]

I am guessing the bike was on the centerstand.

Leaking Petcocks(s) + Leaking floats. Needs to be fixed before it gets into the cylinders, then into the oil.

[speedlimit85]

bike was on centerstand

replaced float bowl assembly last year

[bikerphil]

Verify that your vacuum advance is working, without it the mileage will suffer.

[speedlimit85]

It was not gas. It was old oil from when the oil return pipe was leaking.

How do I verify the vacuum advance is working?

[DiverRay]

You can use a vacuum pump if you have one.
1. Pull the left side crank cover.
2. disconnect the vacuum line from the #3 intake boot.
3. hook up the pump, and watch the lever/plate for movement as you draw a vacuum.
4. once it has moved a bit. leave it and see if the vacuum drops or holds. It should hold.
You can also look at the system with the engine running. Rev it up a bit, and you should see things move.
If no to either, you have a problem.

[bikerphil]

Ray, I think you meant to say disconnect the hose from the #2 carb body.

[DiverRay]

YES! Phil, I did! Trying to write on less than one cup of coffee isn't a good thing for me.

[speedlimit85]

looks good- sucked on a hose to the pod- moved and held pick ups

started with cover off- moving well when revved up

vacuum hoses look good

[jetmechmarty]

I suffered very poor fuel economy a few short years ago. I’ve put over 100,000 miles on my SG. I was getting 25 to 30 miles per gallon. I went through all the obvious stuff. No joy. The fix for me was replacement of the emulsion tubes and the needles. That got me back up over 35 mpg. Reproduction needles and emulsion tubes are available from XJ4Ever.com if you should come to the same conclusion.

[bikerphil]

Yes, what Marty said. I've done this a few years ago too. If you take the diaphragms out of the top of the carbs and the needles have visible wear, this can cause loss of smooth acceleration and reduced fuel mileage. If you do end up replacing them, get the needles and emulation tubes from Len at XJ4ever like Marty stated. They will be exact and not cheap inferior quality which will never work correctly.

[bikerphil]

Hey Eric, did you switch types of fuel recently? The Rec 89 they sell down here gives lower mileage than the 87 ethanol it seems.
Maybe just need a set of spark plugs.

[speedlimit85]

I just changed the plugs and air filter. I try and always use non ethenal 89. I have changed kinds of oil could be a factor.

Before replacing those needles and tubes which are hard to find...I may try valve adjusting and carb sink

[jetmechmarty]

Hey Eric, did you switch types of fuel recently? The Rec 89 they sell down here gives lower mileage than the 87 ethanol it seems.
Maybe just need a set of spark plugs.

E0 is very common around here. I can buy it all over the place and it's mostly 87 octane. People are using it. On a recent road trip (XS650), I tanked up with E0 at a small grocery in a small town. Subsequently, my motorcycle would no longer run at idle. I ran out of gas in the middle of nowhere as the tank ran dry quite early. Yes, an adventure.
If you're buying ethanol free gas from a place that isn't selling much of it, it could be old and causing a fuel economy problem. When I tanked up at a busy Circle K with regular E10, my idle returned to normal and so did my fuel economy. The E0 is just fine at my regular fill-up stops.

[LAB3]

A couple of weeks back I had forgotten to fill my tank and put in one gallon of 93 octane E0 to get me into town since it's all that was available. Generally speaking I put the recommend amount of Seafoam on my tank every 1000-1500 miles just to keep things clean and in this case the 93 octane fuel made the bike bike quite well. At $4.75 a gallon it's not something I'll do very often but that day it really impressed me.