RPM's

[oldbayman]

I've got an 1981 CB 750 F and I'm wondering what's a good range of rpms for each of the gears. What should my rpm be when I'm comfortably in 4th gear? In 5th gear? If I were to try and cruise at a speed of 100 km (55 mph) in 5th gear I think that the rpms would be between 5000 and 6000. Does this seem right? The bike red lines at 9000. What's a comfortable rpm to be using? I ask this because I'm thinking of changing the front sprocket so I can cruise at a lower rpm. Comments please.

[blackhawkrider]

that rpm 5000-6000 rpm is where the motor is the happiest for cruising. It may seem high but that is where the motor produces an ideal amount of hp and torque. If you change the gearing so that it will cruise with a lower rpm you might risk lugging the motor slightly at the worst, or you will find that if you roll on the throttle in top gear at 55mph you are dead in the water with no power to outrun meandering cagers. Slight changes won't hurt anything though but when you say lower I would not change the gearing more than 1 or 2 teath on the rear or 1 tooth up front and not both. Also gearing up can make 1st gear more difficult to use. Just my two cents

[oldbayman]

Hey. thanks for your two cents worth. I figured that if I lowered the front sprocket that it would make first gear harder to use. Maybe I'll "leave well enough alone". You're right about the torque that's available once you're up around 3500 - 4000. I guess I'm just not used to the sound because I'm new to bike riding. Thanks.

[Ruffles]

I'm in the same boat.  My '80 CB750F turns ~6000 rpm on the freeway at about 65 mph.  I'm only getting 39 mpg.  I've got a 60 mile round trip commute to work (mostly highway) and I bought this bike to help save money on gas so I'm looking to add a tooth in front or drop 2 in back to see if I can lower the revs a bit.