45or 48 rear Sprocket Question

[Tony Wohlers]

Hello Sandcast Fellows.
I am not quite shure about too fit a 45 or 48 tooth rear sprocket on the back. I know that Honda changed this sprocket to 48 teth after sandcast and K0. My question goes can I fit a 48 tooth rear sprocket instead off a 45 tooth witouth damaging my short chain guard.

Thank's Tony.
Denmark

[Steve Swan]

Hi Tony,

I am not aware of any reason why you could not use a 48t sprocket with the short chain guard, the only difference i am aware of is the length of the guard which would still clear the larger sprocket. i suppose you could always install the chain, rotate the wheel to make certain there is no fouling.

[imabass]

Tony. Here is a sprocket/gears calculator that I put together for these hondas. All you do is select the stock gears and tire size and the gears and tire szes that you currently have and it will tell you the % variance from the stock. if you go with a larger rear sprocket the bike will be a little more sluggish (less acceleration power). This could be remediated by putting a smaller front sprocket on as well.

http://www.sohc750.net/users/imabass/Honda%20Files/Honda750Gears.xls

[hondasan]

The only problem I encountered when fitting a 48T rear sprocket to a K0 (same chainguard and rear fork as a sandcast) was that if the rear wheel is all the way forward in the fork the sprocket fouls the metal bracket which the chainguard mounts to, preventing the wheel from turning. Just a matter of getting the chain length "right" so that the wheel is not fully forward in the fork.
I would also suggest that if running a 48T rear, you may want to fit an 18T front, unless traffic light drag starts are your thing (in which case go all the way way and fit a 16T front too)!

I believe Yamiya do the 45T sprockets if originality is key here.

Cheers - Chris R

[jaka]

Hi!
The 1969 bikes  (K0) had the 45 teeth rear sprocket and 17 teeth front sprocket.
If you change to a 48 teeth sprocket and keep the original 17 front, the bike will rew more at the same speed and will accelerate better.
But...my opinion is that the original is better as I do not wont a bike that rews as much. Less rpm at a given speed is better!

[hondasan]

My rider sandcast runs with an 18T front, 45T rear. Keeps the revs well down and still pulls okay even two up.
140,000 miles now and still on the original rear 45T sprocket. New 18T front fitted a couple of thousand miles ago.

Chris R.