Introduction and fuel consumption
Posted: Wed Nov 04, 2015 4:29 am
Hello there, Chris from Sydney signing in...
Have just bought a 1983 R100RS in Alaska Blue. 98,000 kms extremely original except for Staintune exhaust and Ikon shocks plus some hideous green fuel hose and awful cheap fuel filters. This is my third airhead in 29 years of riding (previously R65LS 1991-93 and R90S 2000-2002). Very pleased with the bike and am working through the small niggles you always get when buying an old bike (front brake hydraulic lamp switch inoperative, new rear tyre, brakes need servicing, fixing wiring to the illumination bulb on voltmeter) but engine has strong performance, seems to use negligible oil, box shifts very nicely (for an airhead). Compared to my other bikes (all Italian super sport stuff) it is supremely comfortable and serene (which is exactly why I bought it).
However, I did a round trip to Newcastle (400km) last week which highlighted very poor fuel consumption (I think). On the freeway I was travelling at 130-140 or 80-85 in the imperial. Of the 400 km, about 250 was freeway the rest was town riding. I achieved 38mpg. IMPERIAL. My 1970s Italian bikes 850cc and 750cc achieve 45-50 mpg ridden in a similar manner, so I'm not happy with 38mpg.
I think there is a fault and a clue may be that the bike starts easily. WITHOUT CHOKE. It won't start if any enrichment is applied. I have ordered a carb rebuild kit including diaphragms but would appreciate any comments. I have checked the float levels and they shut off the fuel when the floats are parallel to the carb base, so I think they are OK. The bikes pulls strongly and revs all the way to the redline freely. When my R65 suffered a split diaphragm it just would not rev so I am not suspecting split diaphragms in this case. Exhaust tips covered in hard black residue. Looks like running rich, however plugs nice brown/grey colour....
I do suspect the enrichment devices in each carb, but any advice from this group would be much appreciated.
Have just bought a 1983 R100RS in Alaska Blue. 98,000 kms extremely original except for Staintune exhaust and Ikon shocks plus some hideous green fuel hose and awful cheap fuel filters. This is my third airhead in 29 years of riding (previously R65LS 1991-93 and R90S 2000-2002). Very pleased with the bike and am working through the small niggles you always get when buying an old bike (front brake hydraulic lamp switch inoperative, new rear tyre, brakes need servicing, fixing wiring to the illumination bulb on voltmeter) but engine has strong performance, seems to use negligible oil, box shifts very nicely (for an airhead). Compared to my other bikes (all Italian super sport stuff) it is supremely comfortable and serene (which is exactly why I bought it).
However, I did a round trip to Newcastle (400km) last week which highlighted very poor fuel consumption (I think). On the freeway I was travelling at 130-140 or 80-85 in the imperial. Of the 400 km, about 250 was freeway the rest was town riding. I achieved 38mpg. IMPERIAL. My 1970s Italian bikes 850cc and 750cc achieve 45-50 mpg ridden in a similar manner, so I'm not happy with 38mpg.
I think there is a fault and a clue may be that the bike starts easily. WITHOUT CHOKE. It won't start if any enrichment is applied. I have ordered a carb rebuild kit including diaphragms but would appreciate any comments. I have checked the float levels and they shut off the fuel when the floats are parallel to the carb base, so I think they are OK. The bikes pulls strongly and revs all the way to the redline freely. When my R65 suffered a split diaphragm it just would not rev so I am not suspecting split diaphragms in this case. Exhaust tips covered in hard black residue. Looks like running rich, however plugs nice brown/grey colour....
I do suspect the enrichment devices in each carb, but any advice from this group would be much appreciated.
