1981 CB750C Rear Sprocket Change?

[Rider 2022]

I have an 81 CB750 custom. I am thinking of changing the rear sprocket to lower the engine rpms on the highway. (it runs about 5500 at 60 mph). It currently has an 18 tooth front sprocket and 43 tooth rear. Would going to a 39 tooth rear sprocket kill the low end torque? Any advise would be greatly appreciated.
Thanks,

 

[Scootch]

I am not familiar with your bike. I have a '70 K0 750. I changed my front sprocket to 19T and rear sprocket to 43T and changed my speed and RPM by 25%. Of course the torque changes as well. I bought the 19T front sprocket from Cycle X and the rear sprocket from Summit Racing JTSprockets. You can find sprocket calculator on the net. I attempted to attach an Excel sprocket calculator but am not able to. I did attach a screenshot of a calculator that I used when I made the last jump on my bike from 19 teeth on the front sprocket and 48 teeth on the back to 19 teeth on the front and 43 teeth on the back.

 

[BAHNST]

It sometimes takes some testing....post 2 is a good guide...I will say the Dohc do like to rev....its not a harley...500 or even 750rpm wont affect engine longevity by much IMHO.....

 

[Scootch]

Here is a link to a sprocket calculator
https://sprocketcalculator.com/bike-honda-cb750-1970-1982