BMW R80 Carb Rebuild
 

To effectively rebuild the carbs I always replace the following if I do not know the history of the bike:
1 - Diaphragms
2 - Floats
3 - Float needles
4 - Float gaskets
5 - Choke gaskets
6 - Nozzle needles
7 - Needle jets
8 - Four small O-rings / Two on primary jet and two on idle mixture screws.
9 - Two Larger O-rings on the venturi

I also like to add two cables to attach the float bowls on the main housing to prevent them from being lost if they do come loose.
I will shoot a few pics and show you how to do this next time you replace the fuel cables as the old Bowen cable make the perfect cable for the float bowl savers.

When I changed the needles and needle jets on my bike ( 1985 r80rt) it made abig difference to the mpg. from 280 km per tank to 320. ( before needing reserve).

Carb Rebuild. Cost effective?
 

I'm in the process of preparing my 1979 Police R80/7 for the road after a two year lay of. Its done 20 miles in that time, mostly round our communal parking area so has been kept running. However, since there was one or two small issues which were present when the bike was on the road, I decided to do a decent job , short of a complete rebuild.
I started with the obvious de-rust and paint jobs and gradually worked round the bike over several weeks, replacing split rubbers, rusty and tatty fittings, old cables that were really OK anyway, fluids, oils...usual stuff. Generally speaking she was in pretty good shape so not much to do mechanically. Electrically, I tidied up the wiring, new battery, diode board, umteen relays and bulbs and some auxilliary wiring and fuses for external charger and top box running lights.
At this point, it was evident there was a slight problem with the carbs. She was running lumpy and the revs wouldn't drop when trying to change gear making for some crunchy down changes. I swithered and dithered about tinkering with this and tinkering with that until , one day, I got sent a BMW parts catalogue from a seller on ebay. I had previously bought a battery box rubber mount from his ebay shop , not realising he was from devonbmw. (who I had never heard of before) Upshot was, I suddenly became aware of how inexpensive many BMW airhead parts are. Yeh! OK! some bits are a bit over the top but they tend to be bits you would hardly ever, if at all, need to replace. Being the owner of a Yamaha sports tourer. I can assure you that keeping an old airhead on the road is cheaper BY FAR than any Japanese rocket ship I ever owned. Point is, I replaced oodles of little bits and pieces on the old beamer. All those little bits that split, fall off, get destroyed but are not vital so never get replaced. So I did all that and it was still cheaper than two forks seals, a couple of dust caps and a foot peg rubber for the Yamaha. So, having done all that and armed now with a reliable ( and very reasonable cost) source for bits, I set about the carbs with renewed vigour in the knowledge that it was not going to cost a fortune and , even if I mess up and break something, I can get a replacement in the post next day. In the event, I didn't need most of the repair kit I ordered (but good for spares or future rebuild) since the slight petrol dripped ceased after I took the air intake off and tickled the float. I also cleaned out the float chambers and any petrol filters while I was at it. The linkages were cleaned and lubed when I fitted new cables. I also decided to fit new air hoses and inlet rubbers and I'm glad I did because when I changed the inlets, I discovered that one was split. That accounted for the rough running and why ( on this ocassion) I didn't have to rebuild the carbs. I might do it anyway if I run out of other things to do.
Anyway, the whole point of this was from a cost effective point of view and it strikes me that for very little money and a few hours work, you can transform your old airhead. They really run nice when they're running nice if you get what I mean. It doesn't really cost much to get it there either. On the assumption of course that everything else is running OK!
Airhead carb problems seem to feature a lot in travel forums. Most times it is something that a little care and very little money could have avoided. Getting the carbs right on an airhead is really important for smooth runing and good economy. My experience as a newbie is that the 20 quid spent on the carb rebuild kit and little bits and bobs to go with it gave more of an instant payback in terms of improved running than a £300 service on the rice burner. Thats what I call value for money. Now with the money I saved on servicing and wasted petrol, I can go on ebay and buy a set of vacuum gauges so I can balance the carbs more accurately. While I'm there, I'll look out for some shiny engine bars and maybe some nice spot lamps, a tank bag would be nice...perfect for holding the laptop and gps gear, not to mention the mobile phone and pda. maybe even get the mp3 player in there too, I can just squeez it in between the 35mm and the camcorder..
Jeez...motorcycling is really expensive innit!
Glad I own an airhead!
Ian.