Topic: Rear sprocket

[Mark K]

I have 2 sprockets off of 2 different '73 CB750s, one is from my current rebuild and one from a junk frame that I picked up for spare parts. I have purchased a new sprocket for my rebuild.

My question is are either of these two sprockets any good? Or should I take them to the scrap metal place?

Thanks!

[scunny]

The one on the right the teeth are hooked, the left looks ok from New Zealand.

[grcamna2]

Do you have a used chain to install:how's your front sprocket?
Chain and sprockets should be changed as a matched set,if not it will wear-out the chain quickly.

[newday777]

The left looks usable. Is it aluminum or steel?

The one on the right is definitely toast(pointed teeth).

[Tracksnblades1]

Left one looks like it was ran out of alignment.
Right one looks like it was ran with a chain out of pitch…

I’d measure the thickness of the right one and compare with left one..

[PeWe]

New chain with new sprockets is an ensurance of functionality.
Use a new chain on used sprockets can give chain a shorter life.

Another thing if assembly a bike to functional state before a sale.

The right hand sprocket look more like stock and not very worn.

A snapoed chain can cost a lot, expensive engine reoair with good cases.

My blue K6 snapped a chain once. Engine survived. Chain guard with its mounts not. Licence plate got almost sliced. Rear hub and sprocker carrier got ugly marks.

Chain had too much slack. I should have done that the gas station just before.

[Stev-o]

... the left looks ok from New Zealand.

... and the right one looks bad from Texas!

[Mark K]

Do you have a used chain to install:how's your front sprocket?
Chain and sprockets should be changed as a matched set,if not it will wear-out the chain quickly.

Brand new chain, front and rear sprockets for my current build ('73 CB750 Cafe)

Just asking for expert advice if these two 'extras' are worth keeping.

[Mark K]

The left looks usable. Is it aluminum or steel?

The one on the right is definitely toast(pointed teeth).

I believe it's steel, but would have to doublecheck.

Thanks!

[Mark K]

Thanks to all for your expert opinions. I'll trash the one on the right and hang onto the one on the left as a spare.

[PeWe]

I blame my small screen, phone.
Both sprockets look worse than mine when I replace the entire package due to chain.

[Mark K]

Noted, will keep that in mind if I ever have to use it.

[grcamna2]

Thanks to all for your expert opinions. I'll trash the one on the right and hang onto the one on the left as a spare.

Do both of those rear sprockets have the same tooth count?
I'm thinking you can save the one on the left just to try that tooth count to see if it feels like the best ratio,with an already used chain,before you purchase a new rear sprocket of the ratio/tooth count that you will choose;to figure out which ratio works best for you.

[Mark K]

Thanks to all for your expert opinions. I'll trash the one on the right and hang onto the one on the left as a spare.

Do both of those rear sprockets have the same tooth count?
I'm thinking you can save the one on the left just to try that tooth count to see if it feels like the best ratio,with an already used chain,before you purchase a new rear sprocket of the ratio/tooth count that you will choose;to figure out which ratio works best for you.

I'll have to check if they both have same number of teeth. Great idea about using it to get the feel. I've already bought and installed brand new sprockets and chain. Went with the tooth count from the FSM.

[ekpent]

 Did you do 18-48 or 17-48 ? I like the 18 on my bikes but a lot do the 17.

[Stev-o]

Did you do 18-48 or 17-48 ? I like the 18 on my bikes but a lot do the 17.

Hey Eric...I've never done a "tooth change" can you explain why you like the 18?

[ekpent]

Some people like the 17 tooth counter shaft sprocket for getting out of the hole a little quicker and maybe keep the bike up in the rev zone a little higher. I don't do much city or stop light racing so like to keep the revs a little lower in the 5th gear cruise. Think the difference might be around 300-500 rpms or so between the two at say 60 mph.
  Hopefully I got the rear 48 as stock and standard, you know the old memory is fading fast --- 
  If you can keep a secret  and not tell anyone Steve I have even slipped an 18 on the F model 750's which is one more tooth then stock.

[BenelliSEI]

I used to have a box full of “half OK” rear sprockets. Then one day I realized that was dumb and threw them on the scrap pile.

Except for #1250. It’s a low mileage original with a unique hole pattern and correct tooth count. Scrubbed it and reused it for the sake of “originality”. Bikes I plan ride, or sell, get new.

[Tracksnblades1]

Some people like the 17 tooth counter shaft sprocket for getting out of the hole a little quicker and maybe keep the bike up in the rev zone a little higher. I don't do much city or stop light racing so like to keep the revs a little lower in the 5th gear cruise. Think the difference might be around 300-500 rpms or so between the two at say 60 mph.
  Hopefully I got the rear 48 as stock and standard, you know the old memory is fading fast --- 
  If you can keep a secret  and not tell anyone Steve I have even slipped an 18 on the F model 750's which is one more tooth then stock.

Agree +1..

My 76f currently runs an 18/45  with a 130/17 rear tire.
I’ve been chasidized by some for the gearing. At 70mph interstate it’ll
all make since..back in the day I rode with my buddies running 16/48 with 5.10/16 rear tires.
I would be a gear lower in spirit riding, but always within a bike length of the stock Ks that I rode with..

+1 with pitching the 1/2 good sprockets

[Mark K]

Did you do 18-48 or 17-48 ? I like the 18 on my bikes but a lot do the 17.

18-48 is what I went with, based on the parts manual.

[Mark K]

The left looks usable. Is it aluminum or steel?

The one on the right is definitely toast(pointed teeth).

Steel.

[BenelliSEI]

In theory, the larger diameter drive sprocket puts less strain on the chain too...... infinitesimally.

[HondaMan]

A word of advice/experience:
All of the rear sprockets we see today are molded, not cut (if steel). This leaves a fine gritty surface in the teeth, which will wear off in 50 miles and then jam the new chain. This then wrecks the new sprockets, quickly.

To solve this: run the OLD chain on the NEW sprockets for 50-100 miles, first. Then install the new chain. You will get twice as much chain life from that chain if you do this simple 2-step dance.

[BenelliSEI]

A word of advice/experience:
All of the rear sprockets we see today are molded, not cut (if steel). This leaves a fine gritty surface in the teeth, which will wear off in 50 miles and then jam the new chain. This then wrecks the new sprockets, quickly.

To solve this: run the OLD chain on the NEW sprockets for 50-100 miles, first. Then install the new chain. You will get twice as much chain life from that chain if you do this simple 2-step dance.

Thanks for this! Never heard this before but will be trying it very soon!  I do a lot of miles on my 2008 KLR650 and it’s due another set of sprockets and chain this winter. Always surprised they don’t last any longer than they do. I keep them cleaned and lubricatored (most of the time).

Maybe this should be moved to a fresh post so more read it??

[grcamna2]

A word of advice/experience:
All of the rear sprockets we see today are molded, not cut (if steel). This leaves a fine gritty surface in the teeth, which will wear off in 50 miles and then jam the new chain. This then wrecks the new sprockets, quickly.

To solve this: run the OLD chain on the NEW sprockets for 50-100 miles, first. Then install the new chain. You will get twice as much chain life from that chain if you do this simple 2-step dance.

Thanks for this! Never heard this before but will be trying it very soon!  I do a lot of miles on my 2008 KLR650 and it’s due another set of sprockets and chain this winter. Always surprised they don’t last any longer than they do. I keep them cleaned and lubricatored (most of the time).

Maybe this should be moved to a fresh post so more read it??

John,the strong power pulses of Big Single cylinder engine bikes:Thumpers  are a bit rough on sprockets And chains;I'm sure chain and sprockets last longer on multi-cylinder engine bikes.

I hadn't considered what Mark said in his post before:about modern rear sprockets being manufactured "molded"..
I have some NOS rear sprockets from 30 years ago and I see there is a difference between the look of a sprocket being 'machined' compared to the new "molded" look of the rear sprocket teeth of replacements.
I have ordered quite a few rear sprockets from Sprocket Specialists for a few decades and I'm familiar with the look of machined teeth.