Gearing change

Hey folks I've got a question for those of you who have changed your gearing on a CSR 750. So I changed my tires and replaced a spoke the other day and noticed my chain and sprockets are getting pretty gnarly looking so they'll be needing replaced. Idk what the front sprocket is but id assume it's the stock 16t and the rear is stock 38t. I figure while I'm gonna replace them, I'd like to lower my rpms at 65-70 mph as its kinda buzzy at those speeds. Anyone have a part number or suggestions for a lower tooth rear sprocket or even a larger front sprocket if thats a better option? It's an 82 CSR750 twin. 

Here's a couple of quotes by steell. he's kind of knowledgeable on the 750 Twins:

I used a 17 tooth countershaft sprocket on all the 750 twins I have had, but they have all had 16" rear wheels, either Morris Mags or the G rear wheel. And Morris Mags use a 37 tooth rear sprocket stock. end.

17 is a fairly tight fit, to use an 18 you'd probably have to remove the guard in front of the sprocket.
75 mph has been the "sweet spot" (the speed at which everything just feels right) on my 750 twins with the 17/38 or 17/37 sprockets and 16" rear tires. end.

And here's a reply in the same topic by bountyhunter. he's also a Big KZ Twin guy:

Easy to calculate the RPM drop: if you start with a 16T front and go up 1T, the RPM will drop by 1/16 or the final RPM will be 15/16 of the original.
If you start with a rear of 38T and go to 32T (like I did), the RMP will drop by 6/38, or final RPM will be 32/38 of original.
BTW, mine cranked 5000 @ 70MPH stock, so it dropped to about 4200 RPM @ 70MPH after changing the rear sprocket from 38T to 32T.
I don't think an 18T will fit on the front, I know a 32T fits on the back because I am running one now. end.

32 tooth sounds about right then. Any clues for a part number? I don't really want to squeeze a 17 tooth in there if It's very close. 

wrote:

32 tooth sounds about right then. Any clues for a part number? I don't really want to squeeze a 17 tooth in there if It's very close. 

Go to JT Sprockets and look up your bike.  You can get the sprockets off Amazon, or maybe Z1.

www.jtsprockets.com/catalogue/model/s1409/

 

It looks like they list 38 as the lowest tooth rear. They do list a 17 and 18 front though. Maybe ill have to try a 17 then as long as it'll fit without rubbing. 

Moving up one tooth on the front sprocket will make a noticeable difference.  These bikes are designed to spin, so don't nuter the beast.  

Going up one tooth on the countershaft is equivalent to going down 2-3 teeth on the rear sprocket. You can do one or the other and be fine.

Found this. Very interesting. Not sure how exact it is.

www.gearingcommander.com/

I've used gearing commander before and im also familiar with gearing swaps in general. I swapped the rear sprocket on my other bike a couple times for different rides and I used gearing commander to determine which rear sprocket I wanted to try. I guess I'm just surprised about the limited number of options for the rear sprocket on this thing. 

JT isn't the only sprocket company.  You might want to look around for others.

Here’s another option

sprocketspecialists.com/product/rear-sprocket/