Gentlemen,

With fuel prices rising higher each day i decided to come up with something to make my gs even more fuel efficient.

I came up with two wayes: smaller jets or improve (tune) the cylinder head.

For the "smaller jets" theory i thought about using smaller jets in combination with partially blocking the air filter (so carburetion won't be too lean). Downside is that top speed will be decreased but i never go over 140 km/h anyway...

Second, the modification to the cylinderhead. Modifying intake track and combustionchamber could lead to a more efficient burn.

Besides these two options i understand that a well designed fairing will make a difference. Can't think of a lot of other ways to decrease wind resistance.

Anyway, so much for my brainfart. What do you guys think? Any input would be appreciated.

Walk? or make a Electric Bike , or a Diesal Bike

Smaller jets and blocking the air flow will cause engine damage.It will cause detonation,burnt valves and burn holes in the pistons.The GS is all ready jetted dangerously lean from the factory.Many people have head problems because of the factory jetting.If you would like more mpg install a 17 tooth front sprocket.Many have had great results with that modification.Stock should get you close to 65mpg,hyper mileing may get you closer to 75 to 80 mpg with the 17 tooth sprocket.The addition of fairings to an E model will help a little with fuel milage.Just remember that the charging system doesn't start charging till 3500rpm.So you'll need a minimum cruise rpm of between 3500 and 4000 rpm.Only draw back to running low rpm is passing or pulling up hills.You may have to drop down 1 or 2 gears to get enough power.I have used this technique succsessfully for commuting,but I am a sport rider by nature.I was getting 65 to 68mpg on my stock 89GS.Head work would increase the need for more fuel.That's a pure performance modification.I'm not trying to shoot down your ideas.I just don't want you to go into this blind and blow your engine.Plus what I mentioed above is cheap and easier.

QuoteI just don't want you to go into this blind and blow your engine

I won't, that's why i posted the topic.

I now see that the smaller jets/partially blocked air filter won't work. The head mod was a long shot anyway.
The 17t sprocket sounds like a good idea although i have 2 smaller carbs (28mm) somewere. 

Hmmm. I'm not done thinking, yet

PS. a diesel sounds nice but i doubt if the conrods and bearings can stand up to the high forces involved.

Quote from: ben2go on June 27, 2008, 12:54:36 PM
The GS is all ready jetted dangerously lean from the factory.

Maybe in the USA with your stock O1D00 or O1D10 carbs but Holland gets the O1D30 carbs same as us here in the UK. Our stock main jets, needles and pilot jets are different sizes to yours and lean running is not an issue.

A little better flowing exhaust is always a good start on a Naturally aspirated engine.  Not too much though.
A little more advanced timing will improve efficiency, but again a marginal payback.

I would convert to LED lighting for the rear and looks at the possibility of adding LED daytime running lights and only run the high watt bulb at night to ensure proper charging of the battery, thereby allowing you to keep revs down some for cruising along.

Aerodynamics start to really be a problem just above 40 mph. 

The last thing is weight.  Not much to shed on a GS other than cutting back on the double cheeseburgers.

The final word is no WOT and keep the revs down as much as possible.

r

+1 on the shedding weight, aerodynamics and rider input.

if you really want to gain mpg, ride a little slower than the speed limit, be mindful of your acceleration (pace with cars ?) and I'd bet on seeing 10-25% gains. remember, we're already in the 40's and 50's, so 10-25% is a good deal of improvement !

no, you prolly don't want to lean out the mixture more. it's already been pointed out. keep your air filter clean and changed, change your oil, check tire pressures, and mindful of acceleration

good luck !

I can't remember who it was, But someone on here put an 18 tooth counter sprocket on.

From what I remember, the mileage was around 75 MPG on the interstate.

I'm planning on doing the same thing.

The RPM's were still above 5k on the highway so charging wouldn't be a problem.

Be safe.
PJ

If I was trying to save money, I wouldn't have a bike at all. I'm happy to pay for my acceleration, it's why I enjoy riding.

What kind of chain changes would have to be made for a 17t front sprocket?  More links?

Quote from: lewismug on June 28, 2008, 05:30:30 AM
What kind of chain changes would have to be made for a 17t front sprocket?  More links?

I got an 08 GS500F an i swaped the stock 16T to the 17T  the Chain is still stock 520. Just had to loosen the back wheel an retighten with the proper chain deflection it is the easiest swap on our girls.... IMHO.
although after a few other mods my MPG is not as good as it was before . K&N lb an the Yosh RS-3 with the jet kit ...but then agian i am heavy on the throttle ... God how i love to twist it up..almost better than sex!

Quote from: lewismug on June 28, 2008, 05:30:30 AM
What kind of chain changes would have to be made for a 17t front sprocket?  More links?

The stock chain (110 link) would work with a 17 T front and 39 T rear combination.

• required chain length is 110 pitches
• ideal centre distance is 25.531 inches

You can use the following procedure to determine the required chain
http://cgi.stanford.edu/~sanjayd/gs500/Upgrades/Sprocket

(scroll to the bottom of that page for "Calculating Required Chain Length"