sprocket/chain ID and advice needed

Hi guys,

I'm putting a '93 CB750 wheel onto an '83 CB750 (nighthawk). I notice that the rear sprockets are different and i need a little help.

The 83 sprocket is about 9mm thick and the 93 is about 7mm.
The bolt holes line up, so i can just put on the 83 sprocket on the 93 wheel if i wanted to. However, the front sprocket will need to be offset about 3/8 or 10mm so i have to get one that matches whichever rear sprocket i want to use.

The 83 sprocket is bigger, but the tire i plan to put on there will be only 0.6" smaller in diameter than the original 83 tire
(140/90/16 VS 150/70/17).

Since i have to get a new front sprocket anyways, i want to make sure i get the proper kind that matches with whatever rear sprocket i choose to keep.

1. Does this mean the 83 is a 630 chain and the 93 a 530 chain?
2. With the smaller rear sprocket it enough to just get a front sprocket with the proper tooth count so that the ratio remains the same as original? I would prefer this option if possible since the 93 is a bit smaller and lower profile so helps with clearance in the rear.
3. What chain type and store would you recommend that I go with?

Thank you so much!

Just in case you didn’t know and as I’ve seen some people getting surprised by this, I wanted to mention that the same tooth count in 530 and 630 doesn’t equal the same ratio.


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briandk said:

Just in case you didn’t know and as I’ve seen some people getting surprised by this, I wanted to mention that the same tooth count in 530 and 630 doesn’t equal the same ratio.


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Click to expand...

Not sure I get what you mean? Ratio is just a number. A constant. so if the sprockets are both 530 or both 630 with same tooth counts how would it not match?

Would appreciate clarification

chickenStripCharlie said:

Not sure I get what you mean? Ratio is just a number. A constant. so if the sprockets are both 530 or both 630 with same tooth counts how would it not match?

Would appreciate clarification

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You're correct. If you change both sprockets, the ratio stays the same and I should have said diameter instead of ratio.
What I've seen is people trying to go from a 16/35 630 gearing to the same in 530 and ending up with a setup where the chain wont clear the swingarm because of the smaller diameter sprockets.

I had a similar issue when I did my 82 hawk.I swapped to the newer nighthawk rims. The 82 had 530 chain, the 96 had 525. The JT sprockets website helped a lot . The catalog has dimensions,drawings and ratios.

It was there I found the correct offset front sprocket from a different bike. It took some time, but it and a swingarm from another honda allowed everything to come together.

I'd suggest looking up both donor bikes and comparing tooth count, thickness, etc.

530 and 630 chain sprockets have the same width (9.53mm).

I suspect that what people are trying to say is that a 530 chain link is 5 x 1/8ths of an inch ie 5/8" long and 630 is 6/8" or 3/4" so a 30 tooth sprocket for 530 is much smaller that a 30 tooth sprocket for a 630 chain.

Hence a 530 with the same number of teeth may cause the chain to drag on the swingarm. You need sprockets that are close to the same diameter as stock - not the same number of teeth.

Chamberlincraigp said:

I had a similar issue when I did my 82 hawk.I swapped to the newer nighthawk rims. The 82 had 530 chain, the 96 had 525. The JT sprockets website helped a lot . The catalog has dimensions,drawings and ratios.

It was there I found the correct offset front sprocket from a different bike. It took some time, but it and a swingarm from another honda allowed everything to come together.

I'd suggest looking up both donor bikes and comparing tooth count, thickness, etc.

Click to expand...

Thanks! It looks like your rim is exactly the same as mine. So the 96 rim was a 525 chain then?

What did you do for your ratios? Keep the stock ratio but in hr 525 sprocket configuration?

Was the new swing arm because the chain was dragging on it as someone mentioned? Or some other reason?

Thanks!

teazer said:

I suspect that what people are trying to say is that a 530 chain link is 5 x 1/8ths of an inch ie 5/8" long and 630 is 6/8" or 3/4" so a 30 tooth sprocket for 530 is much smaller that a 30 tooth sprocket for a 630 chain.

Hence a 530 with the same number of teeth may cause the chain to drag on the swingarm. You need sprockets that are close to the same diameter as stock - not the same number of teeth.

Click to expand...

Yes but the front would be smaller too, so the ratio should be maintained.

Regardless, your point about the clearance is valid. I will have to look into this as I hadn't thought of it before. Thanks!

In a practical example, on my TR1 I went from 630 16/35 to 19/38 in 530 and still had to shave a mounting tap off the swing arm that would otherwise be hit.

I know 19/38 is not the same ratio as the original, but I changed from 18 to 17 inch rear wheel and had to compensate for that also.


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chickenStripCharlie said:

Yes but the front would be smaller too, so the ratio should be maintained.

Regardless, your point about the clearance is valid. I will have to look into this as I hadn't thought of it before. Thanks!

Click to expand...

Yes. Both sprockets have to change to maintain the ratio.

Let's say the front is 16teeth so that's 16 x 6/8" or 12" nominal circumference. 12/ (5/8) = approx 19 teeth on a 530 chain

At the rear, say stock was 40 teeth of 630, so that's the equivalent of 40*6/5 or 48 teeth of 530. Those are just for example to help you get you brain around it.

Looked at a different way: Original ratio 40:16 =2.50 revised ratio 48:19 = 2.53:1

Go up or down from there, but using the real numbers for your bike.

And if teh rolling diameter of teh new wheel is different to stock, you may want to change the overall ration to suit.

Looks like I'll be putting the old sprocket on the new wheel and sticking to the 530 chain not the later 525. Just to be safe with potential clearance issues.

Old tire is 140/90/16 and new will be 150/70/17.
So about 0.6" smaller. Should be fine with the old sprockets.

Thanks for all the advice. Definitely learned a few things from this thread!

Sorry for the delay in responding to your question, I do not check in often enough...swing arm replacement was do to new tire/rim width, a cb450sc ( small nighthawk) bolted right in, and then I found a 525 offset front sprocket that was close to same diameter to keep things centered. Axle was from the 96, spacers were custom.

Sounds like you are well on your way!