I got my 98 GS500E at the beginning of the summer.  Previous owner paid for a lot of work on the bike, mostly to restore it to stock configuration.  Among other things, he removed an aftermarket muffler and went back to stock, and had the carb re-jetted at least twice, trying to cure a perceived stumble.  I have no idea what jets are there now, but the bike has stock air filter and exhaust.

My mileage is never better than 40mpg, whether I'm out for a highway cruise or a daily commute (35-70 mph, but only 3.5 miles).  It's also never worse than 40.  I have read reviews that suggested 60 mpg as a possibility.  I'm planning to do some long rides on this bike and a longer range (created by better mileage) would be cool.  I'm not concerned at all with increasing the power (or decreasing it slightly with stock jets).

Will the advanced timing mod help the mileage at all?  Would stock jets?  If I do the advanced timing mod, will I need to rejet?

Thanks in advance for any help!

Are the plugs new and gapped properly, and are you sure you are calculating the fuel mileage properly? Post how you are doing it  

I typically get about 45mpg on my '04 "F", but I do a lot of herky jerky off the line starts and lay into the throttle alot. If I ride it easier, I'm sure it would be more - and it is stock, except for the wileyco muffler, but it didn't seem to change my mileage that I'd notice (stock jetting w/ restrictor in the flange).

I don't think the ignition mod would do anything for your mileage, but then again I haven't done it but it does not seem it would. Have you tried carb cleaning or trying a different gas station? Maybe running a bit of fuel conditioner / dry gas?  :dunno:

My '04 is stock jetted and I usually get about 50-55 wringing it out on the back roads pretty hard. I'm sure if I babied her (which I don't) I could squeeze out 60s or so. Around town I wring my baby just as hard, just in lower gears .  

I think 40mpg is very poor for a gs500. You should get between 50-70mpg depending on how you ride. Maybe your bike needs a service, also check if the brakes are dragging by putting it on the centre stand and rotating the wheels.

Quote from: AlphaFire X5My '04 is stock jetted and I usually get about 50-55 wringing it out on the back roads pretty hard. I'm sure if I babied her (which I don't) I could squeeze out 60s or so. Around town I wring my baby just as hard, just in lower gears .  

thats exactly what I was getting on my 2001.

check your tire size as well-that may throw off your odometer. :dunno:

When reading mpg reviews and posts etc we need to be very careful about the country of origin which is not always clear, a US gallon is eight US pints, 128 fluid ounces. In UK and other places still using gallons it is eight imperial pints, 160 fluid ounces. A US Gallon is therefore 25% smaller than a Brit/Oz gallon or looked at the other way, a Brit Gallon is 20% larger.

Depending on certain factors I get 55/60 to a Brit gallon but I do a lot of short hops. When I bought it the dealer said, "You should get at least 50-55 mpg, a lot more if you obey the speed limit"

There have been a lot of posts interested in gas consumption, and I'm detecting a trend.  Most of the pre-2000 bikes seem to admit a lower fuel efficiency than newer bikes.

My 2001 is stock carbureted (no jet kit, no free-flowing air filter, no new exhaust can).  I get mid-50 Miles per USGallon mixed city/rural, and well into the 60's when touring at 50-60 miles per hour.

Consumption is radically worse when colder, as warmup idling and running with some choke on happen more frequently.  But I've never had less than mid-40's even in that instance.

Could be there was a drive to leaner jetting at the turn of the century.  For sure there seems to be a shift to better mileage in recent years.

Quote from: PhaedrusAre the plugs new and gapped properly, and are you sure you are calculating the fuel mileage properly? Post how you are doing it.

snip

I don't think the ignition mod would do anything for your mileage, but then again I haven't done it but it does not seem it would. Have you tried carb cleaning or trying a different gas station? Maybe running a bit of fuel conditioner / dry gas?  :dunno:

Thanks for all the ideas so far.

Plugs are less than a year old, but I personally have not changed them or gapped them.  I'll try that soon.  

I'm calculating mileage using the trip odometer and measuring gas by filling the tank to the same spot on the inlet (on level ground, usually at the same pump).  The milage is pretty consistent, as I mentioned.  If the ododmeter is off on the high side, like the speedometer, I'm really getting WORSE than 40-42 mpg.

I don't use the choke very long and I have checked to see that it completely disengages when the choke lever is returned.

Tires/wheels are stock sizes.

I do accelerate quickly at times, but not all the time.

Maybe I need to look into later stock jets.

My '96 used to get 60 mpg seemingly regardless of how I rode it.  I did a mild rejetting and added BobB's ignition advancer last winter, and the mileage dropped a tad to ~55 mpg.

jeff

My '92 usually got around 40MPG no matter how ridden.  

When was the last valve adjustment? Float level? Stock jetting is 37.5 non-bleed pilot jet, 122.5 main jets. Sprocket sizes? Clean airfilter? Compression test?(do the teaspoon of oil in the sparkplug hole trick first)

I have 40 pilots, otherwise stock. I get around 50-55 on most rides. That short commute might be hurting you, engine may not be warming up completely.

Don't have a leak anywhere do you?  :dunno:

Quote from: callmelennyI have 40 pilots, otherwise stock. I get around 50-55 on most rides. That short commute might be hurting you, engine may not be warming up completely.

Don't have a leak anywhere do you?  :dunno:

The mileage is the same on short commutes and long rides, though, so the warm-up issue shouln't be in play.  Also, when it's 105F (as it is here in August), it gets warmed up pretty quickly!  I usually don't even use the choke in the summer.

I'll look for a leak, and I'll check the float level.  I haven't been into the carbs myself yet.  The previous owner had the work done at a local bike shop -- I tend not to trust any work done by someone else.  They simply don't care about the machine the way I do!

I'm still thinking jetting -- the fact that it starts and runs without a choke in the summer may mean that it's jetted a little rich.  

I'd love to get 55-60 mpg.  That's a 75-100 mile increase in range from 40 mpg.  Thanks for posting your pilot jet size.

Quote from: scratchWhen was the last valve adjustment? Float level? Stock jetting is 37.5 non-bleed pilot jet, 122.5 main jets. Sprocket sizes? Clean airfilter? Compression test?(do the teaspoon of oil in the sparkplug hole trick first)

Are all the years the same in terms of jet size?

AFAIK, sprockets are stock.  Airfilter is clean.

I'll get to the float level and compression test later this winter.

Valve adjustment was looked at by a mechanic under the previous owner (who only owned the bike 1.5 yrs).  Again, I'd like to do it myself and be sure.

Thanks for the checklist!

Quote from: trumpetguyAre all the years the same in terms of jet size?

No.  '01+ had different carbs and bigger jets.  The rejet threads in the FAQ have the info.

I hate to be repetitive, but valve adjustments are to be performed every 4000miles.