I just worked it out from my petrol bills over the past few months.
Over 1744 kms the usage was 5.2 liter/100 kms
Equivalent to 55 miles/gallon
Type of riding: mostly A-roads and mostly 60 mph, some town riding.
My bike is a CB400 NC36 1998, front sprocket 15 and rear sprocket 40 teeth. Factory was 42 teeth on the rear. It would be interesting to see the effects of a further reduction of the rear sprocket to 37 teeth. Hopefully that gives a better economy for cruising.
Cheers, Mansie

that is pretty sweet. I'm only getting about 47mpg on average these days. I ride a 97 race. I've got over 70,000 on the clock and I kind of abuse it. I ride every day, rain, snow or sunshine. I ride in pretty rough urban traffic, but I get out between towns on my daily commute. So I have a mixed bag of riding, from city traffic lights to screaming along at 140km/h on some highway stretches. So I do a bit of stop and go.

Out of curiousity though, I thought if you used a bigger sprocket on the back you would increase efficiency?

a smaller rear sprocket increases efficiency, same goes for a larger front sprocket.
For example: 15 teeth front 45 teeth rear. This means that for every rotation of the front sprocket the rear rotates 120 degrees. If you change the 45 teeth for a 30 teeth sprocket : every rotation of the front sprocket will cause the rear to rotate 180 degrees. (a full rotation of the rear wheel is 360 degrees) So a larger rear sprocket gives less efficiency

Nampus

right, the larger rear sprocket with small front sprocket lets you get off the line quicker....dislexic moment.

dislexic moment.

ROFLMAO can't believe you spelled it wrong!

for the 2 months that i've owned my cb, a recent tank, 2-up on A-roads, with a 14t front sprocket-returned me 59mpg!!!

not bad, but my best on my gull arm before it got pinched was 80mpg.hull to london on 12litres. beat that!

my best on my gull arm before it got pinched was 80mpg.hull to london on 12litres. beat that!

Nope, can't beat that!

My Super Four Version R regularly returns 55mpg, no matter how I ride it seems!

Any more CB400 owners who have calculated their fuel consumption in MPG or litre/100 kms?

I am still not decided whether reducing the rear sprocket size will change MPG a lot. You basically get less Oempf at your rear wheel so in riding style you could compensate with higher revs which defeats the purpose. For same-speed riding in top gear there should be a gain because you ride the same speed at lower revs.

I re-geared my diversion from -3 rear to standard, and lost about 3 mpg from 57 down to 54 (over a pretty long sample). I don't mind losing that, since it made the bike a fair bit more responsive.

I've been keeping regular records for my 1995 Version R with standard gearing / sprockets.

When I bought it, fuel economy was between 45-50mpg, but once I'd run a few tankfuls of Shell Optimax through it to un-bung the carbs/valves etc, there was a marked improvement. I use regular unleaded now, and the economy seems to be staying constant at about 55mpg.

The only modifications to the bike are a Scorpion can and a K&N air filter, which may have an effect but I've no idea how much.