Loss of power and fuel economy

[Guest]

For the last year or so I have only used my '80 GS 1100L to drive around the city and for short trips. This past weekend I drove ~500 miles though. I immediately noticed a major drop in power and fuel economy. In the past I was averaging around 40-42 mpg freeway, this weekend I averaged 30 tops. There also seemed to be very little power at high speeds. When I open the throttle, the RPMs would rise but she really wouldn't pull.

I have since checked the valve clearances and did a compression check. Clearances were good and there was between 140 and 150 psi across all four cylinders. What would be my next test to narrow down the problem? Any help would be greatly appreciated.

(I have a decent set of tools as well as the Clymer manual, so most basic maintenace/tests I should be able to run)

[SqDancerLynn1]

Carbs need cleaning. You could try some SeaFoam in the gas tank

[grantcrose]

Could it be a deeper issue than a simple cleaning? I ask because I thoroughly cleaned the carbs about 6 months ago. Took em off, removed float bowls, jets, etc. and cleaned with carb cleaner.

[lemonshindig]

I would also guess the carbs. If you cleaned the carbs out but didn't address a dirty gas tank, the problem would just come back.

It *could* be something else, but it would honestly be a waste of time to start checking other systems on a whim when it's most likely the carburetors. Tear the carbs down, soak them, put them back together, and if the problem isn't fixed, then we'll think about other options.

Good luck
-Matt

[trickyasafox]

I'm no expert, but that describes my bike exactly pre and post carb cleaning. Not sure if its recommended, but I also installed an inline fuel filter from my tank to carbs - won't help you with a rusted out tank, but won't hurt for most applications either.

[yoshisakan]

Hm, sounds like an ignition problem to me. Check out your points/signal generator. I installed a Dyna S and this fixed the problem for me.

[chef1366]

Check the voltage at the battery with the ignition off and then on.

[chuck hahn]

Air filters getting restricted ( dirty ) can cause weird symptoms..such a running rich, fuel economy, sluggishness to a degree. Just sayin.

[Gregory]

I'm no expert, but that describes my bike exactly pre and post carb cleaning. Not sure if its recommended, but I also installed an inline fuel filter from my tank to carbs - won't help you with a rusted out tank, but won't hurt for most applications either.

Wow I never realized that. I went through several inline filters before I got around to caswell coating my tank. My bike gets poor mileage also.... re-cleaning the carbs.... something to think about this winter.

[matt1100]

What MPG should a GS1100 get?

[trickyasafox]

my 78 gs1000 gets 40-43 if I shift at low RPM. If I rag on it, less.

[Gregory]

My 78 1000e gets around 25-30 mpg. I do have a one tooth larger rear sprocket than stock, but still think I should get better mileage. I haven't been able to monitor myself to drive an entire 100 miles without "ragging on it less"

[chuck hahn]

Greg...Ive rode with you so take this as a compliment please. The way you jack that bike around, 30 IS a good number!!! LMAO.

[trickyasafox]

I should point out too most of my mileage numbers are from highway commuting, so it works in my favor.

[grantcrose]

Here is what I've done in the past two weeks since posting:
-Removed carbs and cleaned again
-Ran an entire can of seafoam through (split across two full tanks)
-Checked the fuel filter, it appears to be clean enough but I don't know exactly how it should look. There doesn't appear to be any large particles or anything.
-Air box... the clymer manual lists that all gs850-1100s, with the exception of the 1000GL models, should have an air filter element. My air box is empty. There is a flat duct for sucking in air that is connected to the box, then the box connects directly to the carbs, no air filter. Is it missing or is this a mistake in the Clymer manual. (I have a '80 1100L)

What is my next step?

Also, can anyone recommend a good place to pick up plugs? I ordered a set of ngk B8ES plugs online but when they arrived I realized that they have a solid terminal, I need a stud type. All of the websites that I have checked don't seem to list the terminal type.