Horrible MPG

[ceccorp]

I got a 78 gs1000, when I got it it barley ran, it was sitting for a long time. I cleaned and rebuilt the carbs, rinsed out the gas tank a little bit, and it has seemed to run alright. I have been driving the bike on the freeway, but having never driven a similar bike I don't really know what to expect, but it doesn't seem to have too much power. I have been getting about 18-20 mpg on the bike, I do drive aggressively and in lots of traffic but couldn't imagine it being that bad. I haven't been able to get the bike much past 80.

What do you think I should do to the bike to get it running strong, or do you think I shouldn't expect much more?

[BassCliff]

Greetings and Salutations!!

Hi Mr. ceccorp,

You should expect much more. You'll find a couple of maintenance lists and links to the proper procedures in your "mega-welcome" below. Let me share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", the Carb Rebuild Series, and the Stator Papers. Now let me roll out the welcome mat for you...

Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[kparkfan]

Welcome to the boards. I would start with a valve adjustment. Did you completely strip the carbs and soak them in carb dip? Just spraying them with carb cleaner wont do you much good. Also replace all the orings in there. Then do a good carb sync and that might take care of the problem.

[MissFabulous]

Yeah, valves come to mind for sure, assuming you did like kparkfan asked and totally pulled them apart, dipped, scrubbed and replaced the o-rings. Also, make sure your (new) plugs are correctly gapped. What color are they now that you've been riding it?

You might also want to do a compression check on the engine. I got a really cheap tester from Harbor Freight - under $10. If your compression is bad then you've got some work to do, but lots of people here to help you through it.

Yes, you should expect much, much more from a GS1000!!!

[Nessism]

For the engine to get such poor mileage it must be running super rich. If the bike has been modified with aftermarket goodies (exhaust and/or pod air filters) maybe someone went too rich on the jetting? Another possibility is the the floats in the carbs are sticking and the fuel level is too high, and/or the petcock could also be leaking down the vacuum line and into the engine.

Before attempting to put a 30+ year old vehicle on the road a little maintenance is in order. A full carb tear down with new O-rings is standard procedure, along with a valve adjustment, fluids change, new plugs/point, ect. Check the carb jets against the manual specs to see if they have been modified. Once you build up a solid base of good maintenance then you can start to hone in on those little problems that crop up (like poor mileage).

Good luck and welcome to the GSR.

[1_v8_merc]

Check the valves and syncronize the carbs.
But first... Is your idle okay? Does the bike vibrate a lot?
(it's going to vibrate pretty good, but I mean excessively)

Excessive vibration in the handle bars and loss of power usually means the valves need to be done.
(atleast it did in my bike)
Vibration in the bike itself usually means the carbs needa be synced.
Because the pistons are fighting each other.

It's also possible your just running really really lean.
I know my 650 gets really weak when it runs lean and dry

it's really hard to diagnose without looking at it.
If you look in the owners manual, there's like 20 different things that can all cause the same symptoms! Lol

sometimes the problem can be something stupid as a throttle cable problem or whatever.

[tkent02]

Just to give you some idea of what you should have, that bike should go 130 something mph and get 40 something MPG, although probably not at the same time. It should accelerate hard any time you open the throttle, especially above about 6,500 RPM.

[chuck hahn]

My 78 100 C has been up to 120 and doing around 65 i have been averaging 36.4 mpg..running above 75 drops it down to around 27. Not saying hes wrong or right, just relaying my findings on my bike..and at 120 i still had throttle left, just knew that back tire was bald and backed off it.

[tkent02]

My 78 100 C has been up to 120 and doing around 65 i have been averaging 36.4 mpg..running above 75 drops it down to around 27.

Tuning, tuning.

[gs11]

Also check the petcock if its the same as the petcocks in the gs1100's mine was leaking into cylinder two , since thats where the vacuum pulled from and caused horrible gas mileage along with number two cylinder not running under 3k rpm. Just something else to look at. I tested mine by pulling the vacuum tube from the carb and sucking on it (Lightly) to see if any gas came out. This would show a leak in the diaphram inside the petcock.

[chuck hahn]

Just did the valves and reset the pilots and air screws properly. Also put in new intake orings. Thing is i just cant help twisting the throttle past 80ish on the highway..no matter how well tuned, she is gonna drink gas faster than if your doing 60. Petcockm isfine and not leaking or functioning abnormally.

[BassCliff]

Hi,

I wonder of the original poster gave up on his bike?




Thank you for your indulgence,

BassCliff

[chuck hahn]

I hope not..too easy to fix once you understand it all.

[Octain]

I hope not too. Unless he's close to me.

[chuck hahn]

dont know his location..never added it.