This manual covers R80GS, R100GS and R100R.
It’s almost the same...
http://www.actiontouring.com/bmwtech/manual.pdf

This is a German partlist for R50-100 and has a lot of nice drawings/exploded views (it covers ”all” airheads from 1969)
http://www.actiontouring.com/bmwtech/parts.pdf

This one is also nice:
RealOEM.com Online BMW Parts Catalog

It’s a great bike, congratulations!

Cheers guys. The theiving ****** that stole my toolkit have been caught and they left me one screw driver and the two spanners mentioned. If I'm going to do the rebuild is it worth replacing all the gasket seals while I'm at it? Is there anything else that you would recommend renewing?

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Buy a carb overhaul kit, only use those gaskets that need replacing.. grease all paper gaskets first. It is worth removing the carbs and holding them in a vice. DO NOT try to replace the needle jets with the needles installed. Replace the jets first.

I reccomend teh Haynes manual, so far it has been accurate

Well I've finally got round to having a look at one of my carbs. I'll do a proper photo and description for the second carb but I thought I'd share this now as there are some issues that I'd appreciate your opinions on.

On disassembling the carb I found that :

1. The diaphram is burst (and looks like it's been that way for a while).

2. The Idle adjust screw broke off under very little pressure, fracturing the casing (but high up - see pics, I'm not certain it's a fatal thing as it's high enough up to not involve the thread). However this presents a problem now as I can't adjust the idle at all (the screw is well and truely bonded in it's original position).

3. It seems that the jet types are wrong (Needle jet 2.64 instead of 2.66, and Main jet is 148 instead of 150). All of this is according to the descriptions for the 1983 R80RT Clymer manual. My bike is registered in April 1984 so I am assuming it is an 1983 model (the first R80RT).

My big question for you is what to do about the Idle adjust screw. Does anyone know anything about the jet sizes also. How can I tell exactly what year my bike was manufactured?

Thanks.

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Also the dust fragments pictured with the main jet above seem to be the remnants of an O-ring. I take it this is a sign that the carb has not been maintained for a long long time or that it got very heated in there at some point? I noticed dark soot on the Air Valve/Slide. Also you can see a slight abrasion on the Air Valve top. Is that something to be concerned about? The Float Bowl also has some build up on it. Someone's obviously scoured around in there too with a screw driver. More pics attached.

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How did you postthe pictures ?

I would say that you need that idle screw to work properly, so one technique is to keep spraying it with WD40 or similar and gently "worrying" it until it frees up.

Also, that looks a lot of "dust" for one O-ring. Got to be muck collected over the years surely?

Dave

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Dave

Hi,
Bit of a newbie here myself and no expert but I managed to do a good job on my R80/7 carbs after reading all the tech tips in this forum, asking the questions you are asking and trawling the Internet for cost effective solutions.
I'm not sure if your carb will ever be 100% efficient in view of the physical damage, that is for one of the clued up fellas in this forum to advise you. However, I can tell you where you will find some of your solutions.

First.
Get the engine and frame number, visit this site, BMW Motorcycle Engine & Chassis Numbers , and you will find the exact model and year of manufacture of your bike. If you don't know where the numbers are on the bike, visit there anyway, then, using the links on the same page, you will be able to find out lots of information about the bike.

Second.
Log onto these sites:
BMW Motorcycle Parts // Welcome
Motorworks - BMW Spares - home
BMW Motorcycle Spares - Motobins Ltd - Hints & Tips
By the time you have waded through their parts list, catalogue, exploded diagrams etc. you will have found every part you need. ( and how much it is going to cost) Remember to check the head to carb inlet rubbers and clips, any ingress of air here will upset the running ( one of mine was split causing rough running and impossible down changes because the revs did not 'die down' when the throttle was closed causing me to suspect sticky linkage or cable). Also check the condition and smooth operation of the throttle and choke cables and linkages. Any fouling or 'stickiness' here can mess things up. Again, cables and ancillary fittings (rubbers, grommets etc) are readily available mail order or from ebay.

Third.
If your carb body is damaged beyond repair, fear not, Bing carbs for airheads appear regularily on ebay so it will not cost you a fortune if you want to replace the broken part. I believe that you can get 32mm Carbs and 40mm carbs. I think your R80 will have the 32mm. There are also domed top and flat top versions of this carb. I have the flat top, you may have different, its just a visual check! (The carbs have numbers on them)
There are at least two or three regulars on ebay who break airheads ( that is a sin in itself!) plus the occasional private seller so you should be able to get a reasonable cost replacement if the carb is broken.

Fourth.
Whether you have replaced the damaged carb or not, the next step ( Judging by the condition of the carbs in the pics) is to clean and overhaul both carbs. The basic overhaul kit is around £16 (pair) and this includes all gaskets, O rings and diaphrams ( Which you definitely have to replace). You can easilly get all the other bits you will need depending upon condition. Floats, jets, needles etc. Needless to say, this is best done by removing the carbs from the bike. (A very simple operation). Do the job methodically, use the proper tools, don't bodge and keep it clean.

Fifth.
When the carbs are overhauled and replaced, you will have to set them up approximately at first. I won't describe it ( I may get it wrong) but this operation has been described in one of these forums before. The bike is then started ( hopefully) and given a ten minute warm up. Then the carbs can be balanced. This is best done with the proper vacuum gauges but, again, various cheaper methods are available. It is very important to get the Carbs balanced properly on an Airhead for smooth running and economy ( etc etc). Before I did this, I filled the tank with fresh petrol of the correct grade and fitted a new air filter at the same time. ( Don't forget to clean any in line petrol filters too)
..
An obvious tip here, if you have removed the carbs from a working bike, don't be tempted to do other work or adjustments like points, timing etc until AFTER the carbs are back on and running. If you adjust too many things while the bike is immobile and it does not start again, it is more difficult to isolate the problem.

Hope some of this may be helpful, I'm sure some of the experts on this forum can fill in the fine detail about which screw to twiddle and by how much.
Just don't forget to visit the sites I have mentioned, especially the bm bikes techie site. All the info you will ever need is right here.

Regards
Ian.

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If you never make mistakes, you ain't trying..

It's an option at the bottom of where you add your message (a seperate box). you can only upload 3 images at a time.

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Thanks Ian most helpful.

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Just a thought but i had a simialar sluggishness above about 60mph on my R80RT which turned out to be petrol tank sealant that had dropped to the bottom of the tank and partially blocked the fuel pipe. A clue was that when going on to reserve it was often difficult to get fuel to flow until removing the petrol pipe from the tap. Hope this might help.
BMW MARTIN

Just returned from a great week's biking in the Outer Hebrides with the R80. I replaced the broken right carb with a second hand one off ebay. I cleaned it but didn't replace the jets, needle, O rings or diaphragm as these looked in good condition. I bought the left hand carb from the same bike also and fitted it to ensure no differences.

The bike now accelerates well through the range (and sits at 85mph on the motorway without any fuss). Previously it had great difficulty getting past 3750rpm. In setting the carbs up I stuck with the recommended mixture settings from the Clymer manual. I adjusted one carb by minus 1/8 of a turn after noticing a sight smoking on the left carb.

The only issue I have now is that between 4000 and 4400rpm it runs a little rough (like it's very slightly out of time on each piston). Above that and below that it's fine. Is this likely to be a needle jet problem? Also can anyone point me to the carb adjustment article I've heard reference to in various places but haven't been able to find. Cheers.

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