Suzuki gs500 gets bad mileage

[bombloader]

My Suzuki GS500 gets 44-45 mpg around town. According to Suzuki, it gets 59 Mpg. Best I've got recently on the highway was 47, and I got 45 the very last trip on the freeway. Now I know that factory mileage estimates are shall we say, optimistic, but I really don't know what is "normal" for this bike. I was wondering does anyone out here have experience with this model. BTW, after the last road trip, I performed a tune-up(plugs and air filter), and haven't done serious highway mileage. Very last fillup, around town, was 44 mpg. I make an effort to improve fuel mileage, but I don't EOC very often, but I do use as little braking as possible around town when I can.

[theycallmeebryan]

Has the jetting in the carbs ever been messed with? The bike could be running rich. Do you need to use choke to start the bike when its cold?

Also, how hard are you accelerating from a stop? Try not to accelerate any faster than cars around you do. Try short shifting to keep the rpms as low as possible.

How fast are you going on the highway? Are you tucking down to make things more aerodynamic?

Whats your tire pressure at?

Just to give you an idea.... my ducati 900ss/sp gets around 47mpg if i baby it. My Ninja 250 has averaged 72mpg since i've owned it.

[bombloader]

I haven't done anything to the carbs. When I pulled the plugs, they were light brown, not black, so I don't think its too rich, but I could be wrong. It requires choke to start if its been sitting for a while even in the summer. I usually shift about 4-5,000 rpm(redline is 12,000). I wouldn't say I baby it away from stoplights, but I usually stick with the flow of traffic. I tuck down as much is as comfortable, I think I'd need to switch to lower bars to tuck lower. Last time on the freeway, I did 75-80, I could have slowed down but I had a deadline.

[theycallmeebryan]

I usually shift no higher than 4000 rpms on my Ninja 250 around town, and i have my bike geared down to 2.60 final drive from the stock 3.21, plus i have taller than stock tires... I accelerate a little faster than 18 wheelers normally do.

I think you should address the carbs if you are really worried about it. I dont know how the gs500's are, but the ninja250 comes rich from the factory. I changed the jetting a bit and it runs a bit leaner now, and performs a little better to boot.

The ducati on the other hand, its a little on the rich side .... because its a play bike

Heres a little write up about your carbs...

http://www.iwt.com.au/mikunicarb.htm

[bombloader]

hanks for the carb info I'll look over it. I also run a K&N filter wouldn't that have the same effect as setting the bike leaner. I've told that you should jet +1 richer if you run a K&N. BTW, you mentioned tire pressure, and I usually run it by the sticker on the bike. My Jeep, I run the sidewall max. Would that have a detrimental effect on a bike, I know there generally more sensitive to tire pressure? The regear sounds like a good idea, my bike screams on the freeway. Engines at roughly 7,000 at 70 with stock gearing. Its difficult to get more options in sprockets, or I would change the gearing.

[theycallmeebryan]

Generally aftermarket filters have more airflow than the stock units, so more air without changing jets will make the bike a little more lean.

(This is mentioned in that link i showed you) You mentioned before that you changed your plugs and saw the coloring on them.....looking at plug color to diagnose how the engine is running only works if you hold the engine at a constant rpm for 10-15 seconds and then kill the engine and immediately pull the plug. If your engine was idling for 10-15 seconds prior to you shutting the engine down before you pulled the plug, all you were diagnosing was idle fuel mixture.

About tire pressures on a bike, it really depends on what you primarily use the bike for. Lower pressures will give you more cornering grip, but more resistance. Also, the steering wont be responsive. With higher pressures, the steering will feel light and snappy, but cornering grip is reduced slightly (this only matters really if you are on a track....racing....)

On my ninja 250, since i primarily use it as a commuting bike, i have the pressure set on the most the tire can handle (i think its 44psi, around there).

Changing the gearing will help. On my ninja im at about 6800rpm at 70mph, and thats after i geared it down! Stock, the bike runs at about 8500rpm at 70mph.... Your bike's acceleration will decrease if you gear the bike down, so you need to consider what you want to use the bike for (fun, economy, or both )

Here are some sprocket options for your bike. Try going up 1 tooth in the front and see how you like it. Its cheaper and easier to change the front sprocket than the rear.

JT Front Steel Sprocket at BikeBandit.com

[bombloader]

Thanks I'll definitely check the plugs like you said. If its too rich, I might just start by removing the restrictor from the air filter. That's easier than taking the carbs apart I use the bike for a mix of commuting and fun, so it probably wouldn't hurt to mess with tire pressure. If I have the money, I'll try the sprocket change after I've fixed everything else I can. Thought about fairings for aerodynamics too, but the ones I've seen cost more than half of what I paid for the bike

[beatr911]

According to GSTwins.com or .org or whatever the GS500's are jetted very lean from the factory to begin with. Installation of a K&N filter can adversely affect on these bikes significantly. It is entirely possible that your jetting has fallen off the too lean end of the acceptable ratio. Along with the other suggestions given, try going back to the stock paper filter and track a few tanks.

Please report your findings so we can learn the effects of all your changes.

Also, the GS can stand taller gearing (like most bikes) for an additional gain. You should be able to go from the stock 15 tooth front to a 17 tooth front and see a good gain.

[Christ]

My friend's brother has a 2000-something GS500-S... he gets around 51-60 MPG, depending on how much he gets on it. I don't think he rides over 75MPH though, except on rare occasion.

[bombloader]

I changed to larger(richer) jets recently after coming to a similar conclusion as beatr911. Posted 64 mpg on an all highway ride shortly after that. Probably an outlier, but hopefully I've got the highway mileage into the 50s again. Haven't got much around town mileage since the change, however, so would like to see what happened to that soon.