HOW many teeth? 15/38 or 15/48?

[Ooldskuul]

On a '79 750k, I would like to change to a 530 series chain.  Currently I'm running a heavy 630 chain.  I like the idea of an Aluminum rear sprocket & a steel front.  Sounds totally logical.  My question is about number of teeth.  The Honda shop manual clearly states 18 tooth front, 48 tooth rear.  But when I check several web sites, all I see is 15/38?  very confused  I'm making the assumption that the shop manual is based on the #630 chain..Yes?

The real question is for a 530 chain on a '79 CB750K , what is the best tooth combination for touring.  I am not interested in high torque from stoplights around town.  Just a good combination for around 65 mph cruising.

Any info very appreciated...Thank you

[shinyribs]

18-48 teeth will run you right at 5,000 rpm at 70 mph. 65 mph will put you at 4800 -ish rpm. I run 18-48 on both of my bikes and like it. It doesn't feel like it is geared extremely low like you might think.Your bike is not gonna pop wheelies and rocket away from stops with that gearing.Though it would be nice! My cafe bike regularly get 40-43mpg with that gearing,and I have gotten 50 mpg a handful of times when riding strictly highway.

A 15 tooth front sprocket,on a 530 pitch chain,is very small in diameter. I've never run one,but the general consensus is that it causes the chain to bind too tight going around such a small sprocket and can wear the chain out quickly. Like I said,no personal experience on that,just what I've read on the interwebs...if you can trust that sort of thing

[Piute]

   On my Bike 77 F2 I've tryed these with stk.43 rear teeth 14 stk r.p.m.'s way to high at standard 65-75m.p.h. ,BUT the 15T seemed great for keeping it tight and rpm's (4th gear)up for thoughs nice long 40-50 curves on a bagged / loaded down bike,Now 16T seemed O.K. if were to stick to interstate and mostly hwy speeds of 70+ (witch is not me) county hwys were 60 speed limit N hitting 70 once in while enjoying my ride, ALSO the cover would not scew back on the bottom hole was covered by the gear I can not see any way anything larger could be put on with a 630 chain like 17T n up. Just finished my report on this subject.

[Ooldskuul]

Thank you Shinyribs.  Man I've been thru so many different gear charts I'm going blind.  It's amazing to me how the retailers that we depend on for correct parts are so careless about doing their homework for bike parts.  Sprockets are a great example.  Every Chart I look at is different.  The shop manual that came with my '79 750 is one from 1974.  Accurate...NOT!
I think that the sprkts I will use will be 18 t. front & 36 t. rear with a 530 chain.  Apparently the original '79 had a 630 chain with 18 t.front & 38 t Rear.
Sure hope I'm right

Once again...Thank you

[Ooldskuul]

Thanks Piute.  First...I'm 110% with you..I hate freeways.  Nuthin there but diesel smoke, gusty winds and NO curves or scenery  YUK!  I just finished a short run over the Beartooth (Both directions) & the Chief Joseph Highway (both ways too).
Been draggin' my butt around with just two wheels for well over 40 years.  All two lane asphalt (if no surprises), and tons of curvy scenery.  

I've read everything I can find on sprockets & I think I may know where I'm at. Apparently the '79 model had a
630 chain, 18t. front with a 38T. rear sprocket.  I'm going to try a 530 chain with 18t. front and 36 rear.  Maybe a 37 rear.  Cycle X has a new 19 tooth sprocket out, but I don't know yet if it will fit my '79 or not.  A 19 /37 might be interesting.
Thank you for your timely response.  For a newbie it means a lot.

[Rodgil]

My 82 CB750FZ had 18/46 sprockets and a 530 chain. I went to a 40 rear sprocket, it dropped the revs at 100km from 5000 to 4100 in 5th gear, and still has plenty of power. 1st gear is now like second, 4th gear like 5th. If you find you can start off in second gear ok, you can go to a 40 tooth rear.

[rich]

I converted my 79K from 630 to 530 also.

I used this handy online catalog to determine the stock sizes for an 80 750K - http://www.jtsprockets.com/catalogue/model/4841. They also have a gear ratio chart at http://www.jtsprockets.com/fileadmin/files/jtgearratio.pdf 

What I like is that it also gives the chain length. I went with 18/46 (same as stock 80) and my RPMs seem about the same as they were with the 630 chain with 15/38 sprockets. Due to the chain pitch, the sprockets are almost exactly the same size (e.g a 15 tooth 630 sprocket is the about the same diameter as an 18 tooth 530). Also, keep in mind if you're going with an o-ring chain that they are a little wider and you could run into interference problems if you go larger on the counter-shaft sprocket.

The DOHC has wide power-band. If you want to be "on the pipe" in the twistys, just drop her down to 4th. That way you can keep your 5th gear RPM low (relatively) for the occasional 70MPH freeway runs.

With the stock set-up (1980-82 18/16 630 pitch) and an o-ring chain, everything fit perfectly and installation was a breeze. The only issue I ran into was the chain I ended up came with a riveted master-link so I had to hunt down a standard clip link for it because I didn't want to drop another $80 for a riveting tool.  

[SoonerRon]

From the Factory Service Manual:





I just bought a new 630, 90 link chain and 15 tooth front/ 38 tooth rear sprockets. Got a great price on old-new stock items on ebay... couldn't turn it down.

[Ooldskuul]

rich wrote

I converted my 79K from 630 to 530 also.

I used this handy online catalog to determine the stock sizes for an 80 750K - http://www.jtsprockets.com/catalogue/model/4841. They also have a gear ratio chart at http://www.jtsprockets.com/fileadmin/files/jtgearratio.pdf 

What I like is that it also gives the chain length. I went with 18/46 (same as stock 80) and my RPMs seem about the same as they were with the 630 chain with 15/38 sprockets. Due to the chain pitch, the sprockets are almost exactly the same size (e.g a 15 tooth 630 sprocket is the about the same diameter as an 18 tooth 530). Also, keep in mind if you're going with an o-ring chain that they are a little wider and you could run into interference problems if you go larger on the counter-shaft sprocket.

The DOHC has wide power-band. If you want to be "on the pipe" in the twistys, just drop her down to 4th. That way you can keep your 5th gear RPM low (relatively) for the occasional 70MPH freeway runs.

With the stock set-up (1980-82 18/16 630 pitch) and an o-ring chain, everything fit perfectly and installation was a breeze. The only issue I ran into was the chain I ended up came with a riveted master-link so I had to hunt down a standard clip link for it because I didn't want to drop another $80 for a riveting tool.

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Sorry to be so long getting back to you Rich.  Both of those websites are good.  One of the few that have the numbers correct.  On the '79 model  the JI gear ratio chart says if I convert to a 530 chain, I should use an 18/38 to maintain stock RPM.   currently...I would still like to try a different ratio.  If I try the 19 tooth from Cycle X (Yes-I will check fit first) that would be quite a change.  I like that.  Or...If I dropped to a 36 rear...I Also like ....But NOT both of course.  If I don't like the ratio's, all I have to do is change a sprocket & I'm off and running.
What's a 70MPH freeway run?

[Ooldskuul]

Rodgil wrote

My 82 CB750FZ had 18/46 sprockets and a 530 chain. I went to a 40 rear sprocket, it dropped the revs at 100km from 5000 to 4100 in 5th gear, and still has plenty of power. 1st gear is now like second, 4th gear like 5th. If you find you can start off in second gear ok, you can go to a 40 tooth rear.

Thank you for the good info.  My 79 gearing is different, but the same rules certainly apply.  I will try your test....soon.
Right now our weather has decided to go COLD for a week or so.  Tonight it's about 21deg. outside & not a hell of a lot better in the daylight.  Awright, awright...I'm a sissy!  In a few days the temp will jump back up into the low 70's & awaaay we go.
That's life in Idaho.

[Ooldskuul]

Hy Shinyribs.  I must have been drunk when I wrote 15 teeth for front.  No way ...just as you say.  It would have to be an 18.
I still want to call Cycle X & check on that new 19 tooth front sprocket.  I spent all day today cussing at my computer over a screwed up download.  Exhausting work. Hopefully tomorrow I'll get a chance.  Too damn cold to ride right now anyway.
Thank you for your input...Greatly appreciated.