Rear chain size to use, KZ750/4 H LTD

I'm bringing back a kind of nice 1980 Kawi 750/4 LTD, and am wondering about the size of NEW drive chain to fit, with sprockets of course..

1. It has 90K-plus km on it, so she's a bit worn.
2. I think the original chain size was 630? Correct me if I'm wrong. That size does seem to have fallen by the wayside.
3. New chains are O-ring sealed, which looks to have advantages for me. Riding is to be generally cruising type riding. I'm retired, so no long rides - but ya never know.
4. What size chain would be good to use? 520?
5. I'm assuming I'd use a steel rear sprocket. While there are aluminum ones, I don' think I'd need them.

Any advice most appreciated.


 

I think 530 is the most common upgrade. For a street bike, I would stick with steel sprockets. 

530 all the way...

Assuming you want to keep the stock ratio
16 tooth front sprocket - JT Sprocket JTF513 series
39 tooth rear sprocket - JT Sprocket JTR488 series
530 chain 102 links long

Z1 Enterprises sells parts like these.

I'd stay with the 630 O ring chain. They are not going away and last longer.
Steve

wrote:

I'd stay with the 630 O ring chain. They are not going away and last longer.
Steve

I'm not sure why you'd say they last longer Steve, for a start there are different tensile strength 630 chains, as there are with all chain sizes,  there are 520, 525, 530 chains that are just as strong or even stronger than any 630. I'm doing a 520 conversion on my bike and the chain i'm using is stronger than most 630's, and about half the weight. Chain technology has come a long way since 630's were used, virtually nothing wears them now days and most modern bikes have far more power than our old bikes.... For example, the 2021 CBR1000RR has a 530 chain and 183 BHP, the Ducati Panagale has 214 HP and uses a 525 chain....

I got 30,000 miles out of the 530 on my ZRX.

I've got a 630 on my 750. It's fine, but pretty noisy - not that I hear it when I'm riding, just when I'm working on the bike. I may swap it for a 530 when it's done, but as it only has 5000km on it that'll be a few years down the track.

Definitely steel sprockets if you want decent mileage.

wrote:

wrote:

I'd stay with the 630 O ring chain. They are not going away and last longer.
Steve

I'm not sure why you'd say they last longer Steve, for a start there are different tensile strength 630 chains, as there are with all chain sizes,  there are 520, 525, 530 chains that are just as strong or even stronger than any 630. I'm doing a 520 conversion on my bike and the chain i'm using is stronger than most 630's, and about half the weight. Chain technology has come a long way since 630's were used, virtually nothing wears them now days and most modern bikes have far more power than our old bikes.... For example, the 2021 CBR1000RR has a 530 chain and 183 BHP, the Ducati Panagale has 214 HP and uses a 525 chain....

530 chains & sprockets use more links/sprocket teeth for the same application so that means the wear in the system is distributed throughout more area so to speak which increases durability over 630.  

Chains don't fail in tension, blown drag bikes possibly excepted, so tensile strength isn't really a thing to concern yourself with.  Tensile rating within a manufacturers family of say 530 chains does go hand and hand with overall quality though, with the more expensive chains being made of stronger material which leads to slower wear.  And speaking of wear, chains don't actually stretch they elongate due to internal wear on the pins.  That's why sealed chains are such a big deal; they come pre lubed so to speak with O-rings/X-rings to keep the lube inside.  

1980 KZ750-H1 Ltd. stock sprockets w 630 chain are 13T Fr & 32T Rr. sprocket ratio = 2.46 (32/13).  
Probably the closest 530 match would be 16,39 or 16,40. 
For longer chain life, you'd want to use the largest Fr sprocket that will fit. not sure if a 17 can be used.
The 39T Rr would lower the rpms a little. not sure how much smaller you can go without lugging the engine, but maybe a 38T.

Most if not all KZ650/750-4 models have the same output shaft, so you can use whatever fits any of those models, such as the KZ650-C1.  At JT Sprockets look up the 650C to see what 530 stuff is available. You could then click the JT part numbers to see what other models used the same sprockets.  Z1Enterprises.com should have the JT stuff or using the model application you can try EB to find other sprockets, such as OEM or Sunstar.  Simplest thing would be to go with JT Sprockets & a quality chain.

wrote:

530 chains & sprockets use more links/sprocket teeth for the same application so that means the wear in the system is distributed throughout more area so to speak which increases durability over 630.  


 

This assumes the pin diameter and the depth of the teeth on the sprockets are the same. AFAIK the 630 sprockets have deeper teeth as the chains have fatter pins. Probably means that there's not much in it when you look at contact area. 
All in all, I don't think this is going to make any difference on modern chains - they will all last long enough if you buy quality. I only have the 630 cause that was what the guy who I get my chains from recommended - didn't think it really deserved much thought for the LTD

A few years back when I went 630 -> 530 the main reason was limited availability of 630 sprockets.  That may have changed but back then I felt manufacturers were phasing out 630 stuff. 

Anyway, 530 was a good choice for me

The 630 has worked well for me. The things I did to it in my Terrible 20's would have broken a smaller chain. 
I bought a gold O ring chain from eBay that didn't make it past 1000 miles. 
It was MADE IN CHINA 
I only buy known quality chains now.
Steve