Fuel efficiency: 55 mpg

[Mansie]

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

[earthbound14]

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?

[nampus]

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

[earthbound14]

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

[alexibrow]

dislexic moment.

ROFLMAO can't believe you spelled it wrong!

[Silva511]

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!

[alexibrow]

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!

[Mansie]

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.

[amorti]

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.

[alexibrow]

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.