Topic: Chain length

[MCRider]

Are you sure the bike is a K6?? The chain length and rear sprocket teeth sound like K7/K8, with 630 chain. These had 15 teeth on the front sprocket. You can verify the chain size by measuring the center-to-center distance on the chain rivets. 530=5/8", 630=3/4".

That's a good question, need to confirm what LongShanks has with VIN # etc.

Then I goofed on the chain length. If stock is 100L, then a smaller front sprocket would call for LESS chain not more. So a 98 could be used. However as Spanner says, he used a 100L on a 17/48 combo. That's what i would do. You'll start with your rearwheel a little further back in the dropouts. But with limited chainwear not calling for the full use of the dropouts, you'll appreciate the extra wheelbase I think.

[scottly]

The K7 630 chain has 88 links, but also has a longer swing-arm. You might have a K7/8 motor in a K6 frame?
Does anyone know off the top of their head if any of the F models used 630 chain?

[MCRider]

The K7 630 chain has 88 links, but also has a longer swing-arm. You might have a K7/8 motor in a K6 frame?
Does anyone know off the top of their head if any of the F models used 630 chain?

The Fs were unified with the Ks. 75/76 = 530. 77/78 = 630

[longshanks]

Ok, so it is definitely a K6. I know I've checked before but I made sure by taking the numbers as follows:

Engine - CB750E-2437857
Frame - CB750-2548729

The VIN badge also says manufactured 9/75 so I assume a K6.

Chain is indeed a 630. Spacing on rivets is 3/4" on center. The wheel as I've mentioned before is a 120/90-18 so is it possible the PO cannibalized a hub from a K7/8 and laced it to my 18" wheel? Or perhaps just switched sprockets? I thought it strange when I found out that one of the spare wheels he gave me turned out to be a 17" with the sprocket side of the hub missing and exposing rubber boots inside the hub(don't know what they're called :/   )

[MCRider]

Ok, so it is definitely a K6. I know I've checked before but I made sure by taking the numbers as follows:

Engine - CB750E-2437857
Frame - CB750-2548729

The VIN badge also says manufactured 9/75 so I assume a K6.

Chain is indeed a 630. Spacing on rivets is 3/4" on center. The wheel as I've mentioned before is a 120/90-18 so is it possible the PO cannibalized a hub from a K7/8 and laced it to my 18" wheel? Or perhaps just switched sprockets? I thought it strange when I found out that one of the spare wheels he gave me turned out to be a 17" with the sprocket side of the hub missing and exposing rubber boots inside the hub(don't know what they're called :/   )

Yikes! At this point anything is possible. had to switch the drive sprocket too, I think.  Could have switched the sprocket carrier from late to early. I don't know all the nuances to the conversion. Usually you see the later bikes being converted to a 530.

[scottly]

Hmm. Please post a pic of the front sprocket, and pics of the rear, from directly behind, showing the relationship of the sprocket carrier to the swing arm and wheel hub.

[longshanks]

Ok,

I'll have to pop off the front sprocket cover to get a look for pictures. I have an impact wrench so the screws should come off ok. Pray I don't strip them! 

[longshanks]

Ok so I took pictures real quick of the rear hub. Let me know if it helps. Also, do I have to pull both covers off to get a look at the front sprocket? Looks like an inner and outer one.
Thanks

[scottly]

Rear carrier looks like an early one with ribs. That's good. The front sprocket cover is the rear-most cover held on with 3 screws; often cut down with only 2 screws remaining because they were such a PITA to remove/replace. I don't bother with it, so I can't help with removal.

[longshanks]

So it looks like the rear hub is a K6? with a K7/8 sprocket on it? Does any of this matter if I'm getting new sprockets and a 530 chain?

[scottly]

So far it looks like you just need to get the proper 530 stuff. Still curious about how the PO fit a 630 front sprocket on a K6 counter-shaft; they mount differently.

[longshanks]

Anyone else want to weigh in here?

[dhall57]

Anyone else want to weigh in here?

Our vin's are very close on our K6's. That's neat. Im not much on changing things up from how they came off the assemble line so I kept the 18/48 sprocket set up when I replaced them in 2010. And went with #530 non o-ring Diamond chain. A lot of members here say going with a 17t frt sprocket gives you a little more pep and tad better acceleration and not has much down shifting, but on the negative side you will be turn slightly higher RPM's on the hwy. I didn't want that so I stayed with the 18 frt.
Here's what my K6 is turning running down the hwy at 60mph

 

[longshanks]

So far it looks like you just need to get the proper 530 stuff. Still curious about how the PO fit a 630 front sprocket on a K6 counter-shaft; they mount differently.

So am I, do I need to measure the chain again to make sure its 630? what about other ways of confirming if its a K6 sprocket carrier?(or hub for that matter) I really want to order the parts (530 chain and sprockets) as it really needs to be changed. Should I just order since it should be 530 anyway and whatever modifications I need to make it revert to stock should justify that, right?

[MCRider]

In my opinion, you want the 530.

http://www.z1enterprises.com/reference/chain630to530.aspx

In my experience, the chains would have 530 or 630 stamped on the side, may have to clean off some gunk.

The 530 carrier had the ribs flaring into the sprocket studs, as you have.

[andy750]

Id definitely get the 17/48 setup - the difference in rpms on the highway is negligible and having a peppier motorcycle from a standing stop is definitely worth it. 

[Hinomaru]

So far it looks like you just need to get the proper 530 stuff.

That would be my vote as well.

Still curious about how the PO fit a 630 front sprocket on a K6 counter-shaft; they mount differently.

I would bet that the OP has one of those aftermarket “conversion kits” on his K6 that were popular back in the day. The old timers will remember these kits since the CB750 suffered a bad rap about breaking the OEM chains and destroying engine cases. The OP has 3/4” pitch chain and a 40T rear sprocket which provides the clue.

[MCRider]

Wow, Hino, that is really cool! Not that i would use or want it. Just that it was there. Probably solves the mystery, too.

[Dave K]

You are right, they did have a bad rap on chain breakage/case damage, that came from the original K0's that had different cushions in the rear wheel. Once that got straightened out, I never heard about anymore problems.

[scottly]

Wow, Hino, that is really cool! Not that i would use or want it. Just that it was there. Probably solves the mystery, too.

1+ Man, where to you find this stuff? Do you live in a motorcycle museum?

[longshanks]

now i just have to pull off the front sprocket cover and determine if its 15tooth. crazy!

what might be the process in converting it back to 530? i have no idea how to pull the front sprocket or change out the rear either(although that seems easier) is there a FAQ i should be looking at?

[scottly]

The front sprocket is easy to replace. There should be a retainer plate fastened to the sprocket with two bolts. Remove the bolts, rotate the plate until it lines up with the splines on the counter-shaft, and it pull it off. Then the sprocket slides off. (does the K6 still have the auto chain oiler?)

[MCRider]

If what you have is the kit Hinomaru referenced, it should be a straightforward swap. I think.

[MCRider]

The front sprocket is easy to replace. There should be a retainer plate fastened to the sprocket with two bolts. Remove the bolts, rotate the plate until it lines up with the splines on the counter-shaft, and it pull it off. Then the sprocket slides off. (does the K6 still have the auto chain oiler?)

No the K6 does not have the oiler, so its just the 2 bolts and the splined plate/holder.

[longshanks]

And for the rear sprocket? Break the nuts loose while the wheel is still in the frame?