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  #1  
Old 22 Oct 2007
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Exclamation R 80 GS power problem
Hi friends,

My R 80 GS Basic (1997) which I am second owner is upgraded by former owner from 800 cc to 1000 cc by changing cylinder heads only.

Nothing has been changed other than cylinder heads. Carbureateur and the spatk plugs stayed same as original.

The result is: on the highway I reach to 140 km/h difficultly and after reaching normal workin temperature. At the beginningi when engine is cold I can't reach over 110 - 120 ks/h easliy. When climbing a hill, I can't get more speed than 100km/h.

I think this is not normal.

I am not complaining and not looking for more speed but when I need speed for overtaking or to reach somewehere or in the highway, it bothers me.

I really don't know what is the normal speed of R 80 GSs with 800 cubic engine? Can they reach a top speed of 180 km/h and ride at speeds 150/160 km/h normally without any problem?

* Should I change carbs for better power (I don't want it to spend more gas, which it is already spend a lot)
* Should I go back to 800 CC (why spending extra money to go back?)

Any advice and experience pls.

Wishing the best,

Sami
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  #2  
Old 22 Oct 2007
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I guess you mean you have change cylinders and not heads?
Unless you have Siebenrock cylinders and pistons it’s not advisable to keep the old cylinder-heads.
Siebenrock is identified by a “S” on the cylinders (upper side, close to engineblock). They are also marked “100” but that also goes for the standard BMW-cylinders.

When my Basic had a standard engine I once managed to get a top speed of 177 km/h (GPS) but it takes time… Up to 150 it accelerates pretty well.

If you have BMW-cylinders I would have changed the heads (or got them modified). The cheapest option might be to get some new heads on Ebay.

When it comes to carbs it depends on what you are looking for, if you want max-speed then bigger carbs are nice, if you want low end torque then keep the carbs you have.

I have ridden an original basic in 150-160 km/h for hours and it’s not a problem, but if you don’t have a good fairing you get tired and there is a lot of noise (wind-related).
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  #3  
Old 24 Oct 2007
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It sounds like the bike is heavy on fuel and looses power at higher speeds.

Before doing anything radical first check the carbs, one diaphragm might have a hole and you might as well replace the nozzle needles and the nozzle jets (needle jets) When these are worn they can cause a lack of power above 4000rpm. Something else to check is the nozzle needles position and, keeping in mind that it might need to be at a different position than the handbooks recommendation because the carbs is now used in a different configuration.

The smaller carbs will produce less power but will be better for fuel economy and will run smoother than the 40mm Bings. I have met some riders that sworn by this configuration so I would not change the carbs.
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Old 25 Oct 2007
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Quote:
Originally Posted by Samy View Post
I really don't know what is the normal speed of R 80 GSs with 800 cubic engine? Can they reach a top speed of 180 km/h and ride at speeds 150/160 km/h normally without any problem?
My 1981 R80G/S would reach 160km/h ...
I'd run at 120km/h all day .. the bike might go faster but that is what I did.


Possibly you have oil in the air cleaning box that is going to the carbys - blocking some small paths .. leading to poor fuel consumption .. look for oil/dirt at the bottom of the inlet to the carby.

What fuel consumption are you getting? That is what I'd be complaining about!
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Old 25 Oct 2007
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Hi Frank
My R 80 GS Basic '97 is 1000 cubic (1 liter engine) with original bing carbs of 800 cc.

I make 450 kms with 35 liter. Sometimes it goes down to 430 (urban) and goesd up to 470 (inter city). Consumption is 12.5 - 13 L/100 kms.

I find it a bit high, but it is 1000 cubic engine.

Best,

Sami
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Old 26 Oct 2007
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Talking Consumption
Frank may be I've written wrong, it is like that:

Consumption is 7.8 litre / 100 km

I think my math is so bad so I am a biker, otherwise would be a professor

sami
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  #7  
Old 26 Oct 2007
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The worst I ever got was something like 13km/l (in sand) .. you're getting 12.8 to 13.4km/l

The best is about 20km/l at 80km/h .. on hard packed dirt.


You have something wrong!
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  #8  
Old 26 Oct 2007
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Have you checked the diaphragms jet?
You can have a look at them without removing the carbs or disturbing the cable settings.
Read the post I added in the ALTITUDE thread about adjusting the needle position, there I explain how to remove the carb tops to remove the piston to witch the diaphragm is attached.
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