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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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  #4  
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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  #5  
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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  #6  
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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  #9  
Old 27 Oct 2007
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Question consumption !

When I asked my technician (who does maintenance) about lack of poer and too much consumption, he recommended to change the fuel nipples (which ejaculate fuel) with larger hole. He said I can have more power and speed but fuel consumption will be higher than this!

I said "please no!". It already spends lots of fuel. And I am really not sure how to look/arrange/fix this consumption problem!

Thank you for explaining how to do it but after having an awful accident wit F 650 in 2000, I started riding this bike just a few months ago. I think I need some time to learn how to do it by myself. Thanks god I have a maintenance book, now need some time. I know it is not difficult but after seeing how to do that

best of all,

Sami
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  #10  
Old 29 Oct 2007
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I want to disagree with your technician on this. Your bike is heavy on fuel because it is running an overly rich mixture meaning that the amount of fuel mixed with the air is to much.
We can rectify this problem two ways, 1st one by increasing the amount of air meaning a larger carburetter with a bigger throat. The next way will be cheaper but maybe slightly more difficult, this is to reduce the amount of fuel getting trough. (Making the mixture leaner.) This will not only decrease the fuel consumption but will also increase the performance.

Someone might have already changed the jet(nipple) to a larger one and in this I can already find one potential problem as the jet must be changed with the needle as well. If only the jet was made bigger then the needle being to thin now, will allow too much fuel through this jet at all rpm even though it is suppose to shut of the fuel supply through this jet below 4000rpm.

Jets and needles is not expensive and I would suggest to buy a few sets to experiment with or if your budged is small lets start with one set and if it does not give you the desired effect then move to the next one.
I hope you understand the problem here is that BMW supplied the carbs with many variations of needle and jet sizes but because they never fitted the 32mm carbs to the bigger bore there is no manual that will give you the correct setup.
I would also recommend a larger main jet 145 part 13 11 1 261 703
The jets fitted to the R80 basic should be: main 135, needle jet 2.68(you can read the sizes on the jet itself.)
To most R100's the needle jet was a 2.66 so I would think to start with this size.
The part numbers is, jet: 13 11 1 261 702 and needle: 13 11 1 338 522.
When installing the needle put it at the fourth notch from the top.
I would check what the carbs was fitted with and replace with the suggested parts to start with.

Last edited by gsworkshop; 29 Oct 2007 at 15:06.
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  #11  
Old 29 Oct 2007
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Exclamation Easier

My technician and any other service is not near than 320 kms.
I have to do everything myself.
Isn't it easier to try to adjust fuel/air mixture first?
Othervice I have to take the bike to service which is not good (350 kms) or technician and better service (700 kms)

Thanks a lot,

Sami

Quote:
Originally Posted by gsworkshop View Post
I want to disagree with your technician on this. Your bike is heavy on fuel because it is running an overly rich mixture meaning that the amount of fuel mixed with the air is to much.
We can rectify this problem two ways, 1st one by increasing the amount of air meaning a larger carburetter with a bigger throat. The next way will be cheaper but maybe slightly more difficult, this is to reduce the amount of fuel getting trough. (Making the mixture leaner.) This will not only decrease the fuel consumption but will also increase the performance.

Someone might have already changed the jet(nipple) to a larger one and in this I can already find one potential problem as the jet must be changed with the needle as well. If only the jet was made bigger then the needle being to thin now, will allow too much fuel through this jet at all rpm even though it is suppose to shut of the fuel supply through this jet below 4000rpm.

Jets and needles is not expensive and I would suggest to buy a few sets to experiment with or if your budged is small lets start with one set and if it does not give you the desired effect then move to the next one.
I hope you understand the problem here is that BMW supplied the carbs with many variations of needle and jet sizes but because they never fitted the 32mm carbs to the bigger bore there is no manual that will give you the correct setup.
I would also recommend a larger main jet 145 part 13 11 1 261 703
The jets fitted to the R80 basic should be: main 135, needle jet 2.68(you can read the sizes on the jet itself.)
To most R100's the needle jet was a 2.66 so I would think to start with this size.
The part numbers is, jet: 13 11 1 261 702 and needle: 13 11 1 338 522.
When installing the needle put it at the fourth notch from the top.
I would check what the carbs was fitted with and replace with the suggested parts to start with.
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  #12  
Old 30 Oct 2007
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The manual you have should give you a good description on how to remove the carbs.
This is very easy and will take about 5min aside, maybe more if it is the first time you do this.
With the carbs completely removed you can remove the tops and pull out the pistons.
To check the needle position you have to remove it. I always count the clicks as I remove the needle because this way I will know if it was incorrect.
There is only four positions on the needle and to remove it you must turn only a quarter turn and pull firmly. After moving for about 1mm it will come to a stop with a firm click.
Now turn it back or forward another quarter turn and pull again and repeating until it comes free from the piston.
To reinstall do the reverse but make sure you push the needle with the first notch parallel to the wire clips in the piston holding the needle. If you don't do this you might push it into the second position without realising.
Move the needle in till it gets to the fourth or last position.

Remove the float bowl and discard the fuel safely and remove the main jet noting the number on the jet.
remove the jet holder into witch the main jet was fastened and shake out the venturi and the needle jet note the small number on the needle jet. (the venturi is the one with the holes in the side and the needle jet is the one with the shoulder almost in the middle.)
The combination between the nozzle needle and needle jet control the fuel mixture between 4000 rpm and almost full throttle. The main jet only control the amount of fuel at full throttle and because you are hardly driving your bike at full throttle all the time it is less important than the needle and needle jet.

Once you have done this post the numbers on the two jets on here and we can see where to go from here.
On the R80GS Basic the main must be 135 and needle jet 2.68
Unfortunately you can do very little adjustment to the carb. the only real adjustment will be to replace these jets.
Dropping the needle one position will make a small difference and will not really solve the problem completely but will go some way to make things better if no parts is available to you.
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  #13  
Old 31 Oct 2007
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I suspect this "technician" has already worked on this bike .. and that is probably it is the way it is (bad)! Part of the joy of airhead ownership is working on the bike yourself. Take the time to learn and you'll be a lot happer with yourself and the bike. I've been getting BMW parts from motobins for way too long now. In most cases they are cheap and in all cases they are speedy. And they usually have a 10% off sale around September so you can buy your servicing parts cheaper then .. BMW Motorcycle Spares - Motobins Ltd - Welcome - there are other firms for bm parts in both the uk and USA too .. this is just the mob I use.

Before you start changing things .. make certian every thing is functioning the way it should be -

Valves (inlet and Exhaust) adjusted ok.

Ignition timing ok and advancing ok

Carbys are clean - no oil blocking the inlet passages - it comes out of the motor into the air box and is routed into the carbys .. can form a sludge that bolcks things up ..

Diaphrams are ok.

Afer that I'd buy two carby overhal kits to replace all the Orings and seals .. while you are doing that wrie down the jet numbers .. and check they are the correct ones .. Siebenrock will have a list.
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Last edited by Frank Warner; 31 Oct 2007 at 03:33.
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  #14  
Old 31 Oct 2007
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Thank You

Thank you very much friends

We will have a look what we can do or if we can do something.

Sami
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  #15  
Old 31 Oct 2007
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Quote:
Originally Posted by Frank Warner View Post
I
Afer that I'd buy two carby overhal kits to replace all the Orings and seals .. while you are doing that wrie down the jet numbers .. and check they are the correct ones .. Siebenrock will have a list.
If the bike has Siebenrock cylinders then the original jetting is fine (have tested this several times on a Basic). This is also what Siebenrock sugests.

But if you have BMW 1000-cylinders and heads it will need rejetting (depending on type of head), if you have BMW 1000-cylinders and BMW 800 heads you have problems which not can be solved by carbs/ignition/valves!

You can identify the cylinders:
-BMW logo and 80 = BMW 800
-BMW logo and 100 = BMW 1000
-S (in a circle) and 10 = Siebenrock 1000
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