High fuel Consumption and low power with my R 80 GS Basic

[Samy]

Hi all,

My R 80 GS Basic '97 has very high fuel consumption and it has very low power.
I spend 7.8-8.5 litres fuel / 100 km (urban). I know it is too much.
Head of the cylinders upgraded to 1000 cc from 800 and standart Bing carbs stays same.
Bike goes up to 120 km/H, difficultly up to 140 km/H and no more and it has so much fuel consumption.

One said I must adjust the air/fuel income with bing carbs by adjusting the large screw.

OK, I try to do that but clockwise or anticlockwise will increase the fuel intake? Whicj one is for air and which one is for fuel?

Anybody can explain me please.

Thanks a lot for any help...

Sami

[Old fart]

Diaphragm with a hole?

[hogmolly]

Too high a fuel level in the bowls can do this. How do the plugs look?

[AntonLargiader]

It may not be a carb issue at all. I would measure the leakdown in each cylinder, check valve clearances, and check ignition timing before digging into the carbs.

In the carbs, the mixture screws are unlikely to affect full-speed fuel economy that much. I'd check the needle position first, and in the course of that you will see if the diaphragms are placed properly and intact.

2.66 needle jet, 135 main jet, 45 idle jet, needle in 3rd clip position from the end.

If worst comes to worst, buy new needles and needle jets. They do wear out over time.

[Samy]

Thank you very much for replying.
My bike is only 43 K kms (I thin 30 K miles equal).
Measures you have given are inches or..?

Thanks,
Sami

Originally Posted by AntonLargiader

It may not be a carb issue at all. I would measure the leakdown in each cylinder, check valve clearances, and check ignition timing before digging into the carbs.

In the carbs, the mixture screws are unlikely to affect full-speed fuel economy that much. I'd check the needle position first, and in the course of that you will see if the diaphragms are placed properly and intact.

2.66 needle jet, 135 main jet, 45 idle jet, needle in 3rd clip position from the end.

If worst comes to worst, buy new needles and needle jets. They do wear out over time.

[Samy]

PART NUMBERS....

Originally Posted by Samy

Thank you very much for replying.
My bike is only 43 K kms (I thin 30 K miles equal).
Measures you have given are inches or..?

Thanks,
Sami

[Grider Pirate]

How long has it been using too much fuel? How long have you had the bike?
When I got my GSPD (used) it used way too much fuel (29 mpg) and wouln't go over 85 mph. The former owner had a Harley background, so he put big jets in. Once I put the correct jets in, it got 42-44 mpg, and will pull redline in top gear.

[charliemik]

I'm betting on valve clearance. Try doing a valve adjustment. They tend to get tight over time and once they do these bikes run like crap. Low power and increased fuel consumption are typical.

[Kokopelli]

Just wondering if there has been any update on the fuel consumption issue. I've just done a search and found this thread, it is asking the exact same question on the same bike I was going to ask. Was there an easy fix? With fuel prices this high it's impossible to ignore.

[opposedcyljunkie]

Originally Posted by AntonLargiader

It may not be a carb issue at all. I would measure the leakdown in each cylinder, check valve clearances, and check ignition timing before digging into the carbs.

agree. timing prolly doesn't reach full advance... easy to check with a strobe light.

[Wirespokes]

The needle and needle jet wear, causing high consumption. The floats get heavy with age and the fuel level goes high causing low mileage.

As with the previous poster - there was some data left out, such as:

Was this a sudden change?

Was there some change made to the bike just before this problem?

How long has this been going on?

And any other data that could pertain.

(I edited this posting to change incorrect data I'd posted previously)

[Kokopelli]

Originally Posted by tvrla

Except for the needle and needle jet wearing causing high consumption, every fault with the carbs makes them run lean. It's possible the float can be set too high, but that took some sort of outside influence. Just naturally, floats get heavy and the fuel level goes low, not the other way around.

As with the previous poster - there was some data left out, such as:

Was this a sudden change?

Was there some change made to the bike just before this problem?

How long has this been going on?

And any other data that could pertain.

This was the first time the bike had been ridden any real distance (1400km) by me. Consumption had been around the 7l/100km mark and I've seen a max of 8l/100km. Not really a sudden change. The bike is on knobblies and had some luggage strapped to it, but not heavy stuff. It was riddenin hilly country at a speed of 100 to 130 km/h.

At home I checked the air filter and it didn't look so good. It has now been replaced. This morning I washed the bike (the adventure ride was yesterday) and have just tried to start it. The battery is now dead, well the relay is ticking, but that' about it. Another mystery, as it is only a few month old and thankfully started the bike every time during some tricky situations.

I may look into getting a carb rebuilt kit and see if that makes any difference.

[Wirespokes]

Sorry about giving you incorrect data in my last post (now corrected). But if your floats are yellow or yellowish brown, they probably need to be changed. They get heavy and don't turn off the fuel flow correctly and allow the level to stay higher than it should.

I don't think well with Kilometers and Liters. I know four liters is roughly a gallon, and a kilometer is about .6 mile but that's about it. I've got a bike right now that reads in kilometers and it's always kind of fun, being different as it is.

Anyway, you've got poor mileage. I got that. Are you using the same 32mm bings that were with the 800cc cylinders. Were they rejetted?

Was the fuel consumption high when it was 800cc?

I'd expect the consumption to go up the faster it's ridden, so that could be part of it. And of course, the dirty filter contributed, I'm sure.

Let us know what you turn up on the electrical problem - nice that it let you down at home and not on the road somewhere.

[Kokopelli]

I've just had a look at the floats, they looked good, not yellow at all. There was a little bit of crud in one of the float bowls.

The picture below shows one of the o-rings. I am a bit concerned about how it is seated. I wonder if that could have an impact.




I couldn't test the result due to absolutely no power, even though the charge seems to think the battery is charged. Not even the neutral light cam on. I got a single "clack" out of the relay. Hope it's not welded itself now.

I wish I new more about this sort of stuff, but I am more into the riding side of things and can do only simple mechanical repairs.

[Eddieb]

Originally Posted by AntonLargiader

2.66 needle jet, 135 main jet, 45 idle jet, needle in 3rd clip position from the end.

Do those figures apply to all Basics or just US spec ones with all the emmisions cr*p in them?

When I got my G/S it had 135 jets in it and only did about 28mpg, it also wouldn't run beyond 60mph.
However it was a UK spec bike and after putting 140 jets in it now runs smoothly to redline and returns ~36mpg.