Topic: '77 CB750A sprockets & chain

[chickenman_26]

Front 15T sprocket for the '77 and '78 model not available from anyone, but there's a 530 conversion kit from Sunstar to convert to the '76 sprockets. Has anyone gone this route? The '76 uses 17 tooth front and 48 tooth rear, but I'm a bit concerned about chain guard clearance. Original rear was 42 teeth with a 630 chain.

Stu

[bollingball]

Don't know if the shaft is different on the (auto) but I got my 15T for my K8 from DSS. Mine has the one larg bolt through the center.

[raymond10078]

Just checked BikeBandit - they have a 630 front sprocket (aftermarket JT Steel) for less than $20.

UPDATE:  I ordered the sprocket - and as stated later in this thread, it is NOT the right sprocket.  BikeBandit clearly states that the sprocket that they are selling is for my bike (78 CB750A), but it is not.  Will be returning it.

[raymond10078]

Also - FYI specific to your original question/issue.  A 48 tooth 530 sprocket is smaller in diameter than a 42 tooth 630 sprocket, so your concern about your chain guard is not relevant.

I may also move to 530 chains/sprockets some day (due to cost, not arts availability), but . . . I kind of like the look (as in MEATY) of the big chain.

[chickenman_26]

Also - FYI specific to your original question/issue.  A 48 tooth 530 sprocket is smaller in diameter than a 42 tooth 630 sprocket, so your concern about your chain guard is not relevant.

I may also move to 530 chains/sprockets some day (due to cost, not arts availability), but . . . I kind of like the look (as in MEATY) of the big chain.

Thanks. I'm aware of the size difference. But I won't have the answer for sure till I bolt it up. The swingarm and chain guard for the '76 are different part # than the later models. Someone above said Bike Bandit has the JT sprocket, but that's not true. JT doesn't make a front sprocket for the automatic after '76. Never did. Western Powersports (wholesaler) has a catalog error, and all the dealers I spoke with think they can get it. So I let one try. What arrived was a sprocket that fit a '77 CB750F that needed to be held on with a nut on the shaft - it had no threaded holes for the retaining tab. It was also 2mm too thin with a raised boss on one side only.

BTW, the Sunstar 530 "conversion" is using a front sprocket that has the boss thicker on one side. It's supposed to be for '76 through '78, and they say to mount with the shorter side toward the engine on '77 and '78 models. This made me reject their kit. So I've ordered a set of standard sprockets for a '76, and I'll shim the rear as necessary. I'll let you know how it turns out w/pics. Thanks to all for the replies.

Stu

[chickenman_26]

BUMP

It was a plug & play proposition. The 530 sprockets are exactly the same width as the 630 ones, so no shimming required. The only drama was with the JT front sprocket not fitting the counter shaft properly. It would go maybe 2/3 of the way on with the logo facing out. Flipped it over, and it wouldn't go on at all. Cycle Gear here in Phoenix told me they've had so many complaints like this lately with JT sprockets that they've switched to recommending Sunstar instead.

Stu

[Danno]

i did a sunstar conversion on my 76 a to a 530 chain and i know what you are saying about the boss on the front sprocket is true but the harder sprocket will work just fine I was iffy too but it really did work well and that bike has seen 105mph several times