Chain And Sproket Inquiry

Hey Guys, I need some of your vast knowledge and advice. Its been a while since I posted! I've had my 78 KZ650 for almost 10 years now, and its been my most prized possession. Its been a point of pride that I've performed all the maintenance and repairs myself, (except mounting/balancing tires). However now i'm finally due for new chain and sprockets. Now my bike is far from stock, the previous owner/owners have modified it extensively, and as far as I can tell its likely made out of several bikes. The chain and sprockets on it now are as follows: 33 tooth rear sprocket, 14 tooth front sprocket. The problem I'm having is, I've only come across 1 properly spaced 33 tooth 530 pitch sprocket for sale, and its pretty dumb looking ( www.orientexpress.com/p-14555-vortex-rear-sprocket.aspx ). Another option i'm considering is just either going back to stock sprocket sizes, or maybe just selecting the smallest rear sprocket I can find. The gearing setup that is on the bike has seemed fine to me all these years, and i'm really in no hurry to change it. I'm also probably just used to it by now! I'm also considering the possibility that my sprockets were sourced from a 1981-1983 kz650 CSR with the 630 type chain. Ok, so even after I get all that figured out, I still cant decide to go with an X or O ring type chain .. I'm also considering just dropping it off at the shop and being done with it! What do you guys think? What would you do?

Thanks - Alex

Stock is a 530 chain w 16T Fr & 42T Rr. JT Sprockets has those sizes, plus a few others. Z1Enterprises.com should have them.
JT lists the ratios in a handy chart right there on the page for your motorcycle. see link below for the KZ650B.
Assuming a 78 KZ650 revs about the same as my 81 KZ650-CSR, I would probably go with a 16T/40T setup to lower the revs a tad.
To extend the drive chain life it's best to install the largest Fr sprocket that will fit. I don't know if a 17 or larger Fr will fit, but a 17/42
would lower the revs as well.

www.jtsprockets.com/catalogue/model/s1398/

Assuming that your bike is a 1978 KZ650-B2 the front sprocket would have originally had 16 teeth and the rear sprocket would have had 42 teeth. The correct chain size for a KZ650-B model is 530. The original chain was an endless link type EX50MV-0X102L that had 102 links. The rear tire would be an 18” one.

If the previous owner installed a different swing arm, rear tire, chain, sprockets, or who knows what all bets are off. However, if I was planning to return the bike to a somewhat original condition I would install the original size chain and sprockets and if it had been changed I would install the correct rear wheel. Ed

I ended up getting a 16 tooth Sun star off Ebay as the JT sprocket has no hole for the retaining lock washer. Edit...... after looking at the Jt catolog I see they added the hole. The one I got from Z1 around 6-7 years ago didn't.

Sprockets and chain are easy to replace. I've done mine since forever.

Your current ratio is 33/14, or 2.357. According to other posters the stock ratio is 42/16, or 2.625. To keep your current gear ratio you will need a rear sprocket with 38 teeth. This would give you a bit lower rpm at highway speed compared to stock. If you want to go back to stock you will need one with 42 teeth. You should be looking at 530 chain and sprockets.