81 GS750L: **** poor fuel efficiency

[Guest]

Bottom line: I'm getting only about 75 - 80 miles a tank.

There are no obvious fuel leaks anywhere. My engine oil level is not rising and does not smell like gas. I'm just trying to find out where to start looking.

My first thoughts are piston rings and then valve adjustment. Does anyone concur with that? My carbs are all at stock settings. I use pods but closed them off until I reached stock performance with them on. The bike seems to run fine all around except for the bad mileage!

[Rijko]

agreed, valve adjustment first, compression check next, are a good starting point.
Carbs rebuild.
Intake o-rings need replacing if not done already.

If more or less at stock performance anyway, using the stock airbox would probably be a big improvement and would take the pods out of the equation.

[gullywhumper]

agreed, compression check and valve adjustment are a good starting point.
Carbs rebuild.
Intake o-rings need replacing if not done already.

If more or less at stock performance anyway, using the stock airbox would probably be a big improvement and would take the pods out of the equation.

I know about the pods. I just have to work myself up to paying 80 bucks for 4 pieces of rubber. It hurts.

[Rijko]

o-rings are real cheap : http://www.cycleorings.com/intake.html

[glib]

...80 bucks for 4 pieces of rubber. It hurts.

Agreed. If I understand how you blocked of your pods, I would think that it would be nearly impossible to get the fuel/air mixture close. Sounds like you are either going to pay for the rubber, a jet kit or extra fuel--the 'ol "pay me now or pay me later."

[Rijko]

intake boots, even when hardened, usually seal well.
It's just the o-rings i was talking about.

Air filter box may not be that expensive.

[Rijko]

check this guy http://www.thegsresources.com/_forum...50-Reboot-2016

or ask in the parts wanted section

[Steve]

Intake o-rings need replacing if not done already.

o-rings are real cheap : http://www.cycleorings.com/intake.html

Even at that "real cheap" price, it would be a total waste, in his case. His bike does not use them.

Gullywhumper, I have to ask one other question. What is your typical riding speed?

OK, another question or three:
Besides your terminal velocity, how hard do you accelerate?
Do you carry a passenger?
Is your 'gravitational attraction' sufficient that it seems that you are carrying a passenger all the time?
Do you have a windshield on the bike?

All of these are simply physics-related questions. It takes more energy (gasoline) to accelerate a given mass at a given rate. Even more energy is required to accelerate that mass at a greater rate.

As far as speed is concerned, it's simply a matter of how much air you are pushing out of your way, and how hard you are doing it, because aerodynamic drag increases with the square of the increase in speed. I have a fully-loaded touring verson of an '80 850G that you can see by clicking the link in my signature (assuming my Photobucket account still works ). When riding 'normally', with speeds in the 55-65 mph range, my mileage is typically in the low 40s. A couple of weekends ago, I rode home quickly from an event. Not going to brag about top speed, but let's just say that I was seldom under 80 mph, unless I was in town or approaching a controlled intersection (stop sign or light). According to my GPS tracks, I covered 75.4 miles in 1 hour, 4 minutes, 35 seconds from the time I started the bike until I parked it at home. That was an average of 70 mph for just over an hour. When I filled the tank, mileage was a whopping 26.6 mpg. Speed has a LOT to do with mileage.

I have also related our experience a few years ago with my wife's 850L (also seen in my signature). We were with our Goldwing chapter on a ride to West Virginia. They were trying to get to a restaurant before the lunch menu prices expired, but got a late start, so they were riding about 70-75 mph. Not so bad, but we were going into a headwind of about 20 mph. The first two tanks were 28 and 29 mpg on her bike. Later on the trip, coming back through Kentucky on the way home from Virginia, she got three consecutive tanks over 55 mpg, with no adjustments to the bike, just lowering the speed from an apparent 90 (counting the headwind) to a more-reasonable 55-60.

Valve adjustments and clean carbs will help ensure your ability to reach those numbers.

.

[Rijko]

Even at that "real cheap" price, it would be a total waste, in his case. His bike does not use them.

ugh .. good catch Steve, my bad