Topic: what does the sprocket size affect

[Xander^]

so... im kind of a newbie to the whole motorcycle world but ive been learning very quickly thanks to alot of you guys.. which brings me to my next few questions in my rebuild.

With needing to put a cb750 1972k bottom end on my 77 top end, some sprocket ideas came up to make sure this swap will work. so i wanted to make sure i got the right stuff.

i wanted to know what the stock sprocket sizes were for the rear wheel and the small inner sprocket?

and, what is the difference switching from the stock to a 630 sprocket? (which is what i learned was needed for my engine swap)

and, if i switch the sprocket on the rear wheel to 630, do i have to change out the inner small one also? and to what size?

lastly, a couple months ago i bought an O-Ring chain athat was 630 -90 links. will this work still if i switch stuff up?

sorry for all the questions, but im losing my mind lol!

[HondaMan]

The 630 chain will require the 630 size sprockets, and vice-versa for the 530 chains/sprockets.
The 72 bottom end uses the 530 sprocket, so the rear sprocket would have to match that, too.

The 72 engine used the 18T front sprocket (17T will also work if you mostly ride in town), and the rear sprocket for this one is 48 teeth (which is likely what you have, if it is a K2).

If you change to the 630 chain/sprocket setup, you'll have some work cut out for you to find a 630 rear sprocket that will fit the '72 (K2) rear hub. I'd suggest staying with the 530 setup, if possible, if for no other reason(s) than the sprockets are cheaper, the chain is, too, and the K2 bottom end started out that way (so did the chassis). If you use the 530 chains from Diamond you will get the longest life per $ spent.

[Xander^]

The 630 chain will require the 630 size sprockets, and vice-versa for the 530 chains/sprockets.
The 72 bottom end uses the 530 sprocket, so the rear sprocket would have to match that, too.

The 72 engine used the 18T front sprocket (17T will also work if you mostly ride in town), and the rear sprocket for this one is 48 teeth (which is likely what you have, if it is a K2).

If you change to the 630 chain/sprocket setup, you'll have some work cut out for you to find a 630 rear sprocket that will fit the '72 (K2) rear hub. I'd suggest staying with the 530 setup, if possible, if for no other reason(s) than the sprockets are cheaper, the chain is, too, and the K2 bottom end started out that way (so did the chassis). If you use the 530 chains from Diamond you will get the longest life per $ spent.

interesting,

well kind of confusing sorry, but ill only be using the bottom end motor of a 72k .. rest of the bike if 77k

[754]

 Hondaman why would the 630 rear sprocket not fit the carrier.?
You can run  530 or 630 on any year from 69 thru and including 78.
 If your question is actually referring to 630 vs 530. That is called pitch, not sprocket size.

[Jerry Rxman Griffin aka MuthaF'er]

There is a 10mm offset at the output shaft between the 77 (+10mm) and the 72 (-10mm) you will have to deal with front to back.

[MoMo]

do I understand you to be saying you are using a 72 bottom end and a 77 top end? ...Larry

[Xander^]

There is a 10mm offset at the output shaft between the 77 (+10mm) and the 72 (-10mm) you will have to deal with front to back.

interesting, ok so what will i have to do to account for that to make sure this swap will work?

[Jerry Rxman Griffin aka MuthaF'er]

Depends on which parts you are using on which bike. I used a late engine in an early frame. I changed everything behind the front sprocket by that 10mm offset. Late Swingarm, sprocket carrier, chain guard. The upper shock mount needed attention too. I went with 530 instead of 630. The front sprocket mounts differently on the 77/78 engine too which is OK but the 630 sprocket on the late engine does not have the two shoulders the 530 sprocket does. If you used a 530 sprocket it would push it more out by the width of that shoulder. I found that the CB650 530 sprocket to work without the shoulder.

Soooooo, you haven't provided enough info on your plans for us to do more than speculate.     

[754]

First off decide which chai  you want to run.
 I can't find many reasons to run 630 anymore.
 I would run 530 myself .
 
I re read first post..see that you have most of the 630, May as well use it up..

[MikeSimon]

Although it is a little hard to read I agree with 754. I would not use a 630 set-up. It is outdated and just eats power. Even for the CBxes, where the 79 came stock with a 630, everybody changes to a 530.

[Xander^]

Depends on which parts you are using on which bike. I used a late engine in an early frame. I changed everything behind the front sprocket by that 10mm offset. Late Swingarm, sprocket carrier, chain guard. The upper shock mount needed attention too. I went with 530 instead of 630. The front sprocket mounts differently on the 77/78 engine too which is OK but the 630 sprocket on the late engine does not have the two shoulders the 530 sprocket does. If you used a 530 sprocket it would push it more out by the width of that shoulder. I found that the CB650 530 sprocket to work without the shoulder.

Soooooo, you haven't provided enough info on your plans for us to do more than speculate.   

ok i see what youre saying.. well this is kind of getting confusing. lets just restart a bit.... my bike is a 77k, except for the bottom end of the motor, i had to get a 72k bottom end because the 77 had a few issues... so i needed to know what will this do to my bike and what i need to do to make the 72 bottom end work with my 77 top end (motor only)... rest of the bike is original 77.

[754]

Son you need to offset front sprocket..
 Or move rear in 10mmm using the earlier carrier and inner spacer  plus add an axle spacer.
 Not sure if the 77 chainguard will work.

[HondaMan]

.. rest of the bike is original 77.

What he ^^^ said (754)...the rest of the '77 bike will make conversion to the 530 chain size somewhat tricky unless you're well-versed in the details.

[MoMo]

Cases are matched so using a 77 top end with a 72 bottom end will be quite difficult to make work...Larry