Topic: Sprocket alignment between K6 Engine and K7 rear

[Kaze]

I read an ancient post here somewhere, about a guy like me who put a K6 or older engine in his K7 / K8 frame.
There was discussion about alignement between the sprockets, because the K7 / K8 swing arm is 1cm wider (to line up with the K7's front sprocket...shaft, which Honda decided to stick out 1cm more). My take-away from the post was that in order for the guy's sprockets to line up correctly, he should go find himself a K6 or older rear sprocket carrier.

MY bike has a K6 engine in a K7 frame with a K7 swing arm.
Both sprockets and chain are K6 spec. (18-48, 530x100 chain)
Rear wheel (axle, etc.) is K7, tire is 130/90-17.

EDIT: My sprocket carrier is also K7.

1cm seems like a big deal, especially at highway speeds, and this has me concerned.

Is there a way I can check to make sure my sprockets are in line? (One that doesn't involve expensive laser-guided tools)

[bert96]

 

 Check this Lazer guide. Pretty cheap and it work!

  https://www.nc700.co.uk/index.php?/topic/12553-profi-laser-chain-alignment-tool/


 Bert

[Kaze]

Cat-toy laser, zip-tied to a chain alignment tool. Somebody is certainly clever. Thank you! Dollar Tree, here I come.

[scottly]

MY bike has a K6 engine in a K7 frame with a K7 swing arm.

Rear wheel (axle, etc.) is K7, tire is 130/90-17.

To use your K6 engine in a K7 frame, use a front sprocket with a 10mm offset.

[Kaze]

Is such a thing common for Hondas, or will I need to have one made?

[PeWe]

Change rear sprocket carrier to earlier will not help?

Chain will scratch something?

[Kaze]

Now the trick will be to find an 18T sprocket that matches my spline AND has the 2 holes for 76'.

EDIT: Bert found me one on Ebay. Thanks Bert.
https://www.cafr.ebay.ca/itm/325731417137?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=z4AFM0A4TyK&sssrc=4429486&ssuid=PMkiLDiKSkW&var=&widget_ver=artemis&media=COPY

[seanbarney41]

Now the trick will be to find an 18T sprocket that matches my spline AND has the 2 holes for 76'.

this is the standard sprocket for 71-76 cb750k1-k6

[Kaze]

Whether I bring the front sprocket out, or the rear sprocket in, the chain will hit something.

I've talked to a guy who put a 10mm offset front sprocket on his older model CB750K. He said that the chain rubbed on the inside of the front sprocket cover, so he had to remove material (all the way through it). I want to avoid cutting up parts if I can help it.

It turns out that I have a K7 hub, aka sprocket carrier. The K6 and older hubs are visibly shorter than K7's, though I don't know the exact measurement. If I buy a used hub from an older K model, there is a chance I might have to give up my chainguard. That sucks, but it's better than cutting up a front sprocket cover.

Q1. Does anybody know for sure whether my axle or spacers will need to change if I change the sprocket carrier?
Q2. I know there are old posts on putting F2 engines in old K frames, has nobody done it the goofy way I'm doing it?

[seanbarney41]

I had a K7/8 engine in a k5 frame.  I used the k5 rear sprocket carrier but with a 10mm offset rear sprocket from CycleX and 530 chain.  I don't believe they offer this sprocket anymore.  The tightest spot for chain clearance was right at the rear shock.  I did not run a chain guard.  I think I could have used a chain guard with a slight bend to the mounts but you would then have to remove a pretty good chunk adjacent to the rear shock.  The front sprocket cover also has a slight variation between K0-k6 and K7/8.  It's a very subtle change but the K7/8 cover gives more room.  I don't think the covers can interchange...not sure.  Also pretty sure  what you plan will require different wheel spacers.  It's tough to wrap your brain around it without having all the parts sitting there n front of you.  Lots of washers and spare spacers to turn/grind down will get it done easy once you see where things are at.

[Kaze]

"It's tough to wrap your brain around it without having all the parts sitting there n front of you."
You can say that again. How the heck did anybody even know they weren't aligned? Looking down the chain, I honestly can't see a 1cm misalignment between my sprockets. Do you reckon it rides differently?

I bought a chain alignment tool and tried it out today. But all that does is show me that the chain goes straight back from one sprocket to the other. It doesn't show if the sprockets themselves are aligned.

20 years ago I put my K7 engine into a K6 frame because I had crashed and needed another frame. Everything bolted up just fine, so I did it, and rode it. Of course, I was invincible then. It was very nice out touring?

Anyway, I saw an older K sprocket carrier on Ebay for about $30... and I actually have a K6 axle and spacers in my shed in case I need different spacers. I might just "try it and see". But again, I don't see how I'll be able to tell if it's aligned.

Any word on how I'll know if it works?

[newday777]

Have you tried to use a straight edge against both sprockets? Probably have to remove the shock, chain guard and chain. Just have to have a clear path for the straight edge, might have to customize it to fit.
Push the straight edge tight flat against the rear sprocket surfaces, does it touch the front sprocket or run parallel with the front sprocket equally? A laser pointer can do it if you set it up on a pivot carefully.
You will need a K2-K6 rear sprocket carrier.

[RAFster122s]

I got kicked out of a QC job on a CRT and flat screen refurbishment facility I worked at because I was detecting 1mm of curvature on the alignment of the screens coming out of repair. The engineering staff was disagreeing with me on the sides having a curve and an engineer had a small 6 in shirt pocket metal rule with one side measuring mm and the side in inches. They measured it and saw I was right and were pissed off.
I guess my Mark 1 calibrated eyeball was better calibrated than theirs.
What can I say…I’m an artist and have always been a detail person with an extremely good eye for detail.
This was when I was between jobs and had taken a temp contractor job to help us survive until I found another position in my field of expertise.

A laser that gives you a beam you can project down an alignment rod beside your sprocket or on your rear sprocket can help you see and measure the difference between front and rear sprockets.
Just be careful with your rear wheel alignment from side to side on the swing arm, you can introduce variation if the rear wheel is cocked from one side or other in the swing arm.

[Kaze]

Mornin'
First thing, the laser pointer I got only projects a dot, which is what I get for buyin' cheap cat toys. Moreover, the cat doesn't even like it. She looked up at me as if to say, "Why are you doing that?" Apparently, for shooting sprockets I need one of those lasers that will get me arrested if I point it at airplanes.

Second, I bought a 74'* rear sprocket carrier / driven flange / final flange off Ebay for $34 (half that was shipping). The old 'Bent Bike' salvage shop in town here is gone, so I gotta pay the ships.

Third, why does shipping come in a truck, but cargo comes by ship?

(* Yes, I checked. K4 & K6 have the same part number)

[Kelly E]

The old 'Bent Bike' salvage shop in town here is gone, so I gotta pay the ships.

You live in the Lynnwood area? I went to the going out of business sale. Met the owner who told me that "his lazy kids don't want to work" so he liquidated the inventory. I miss that place.

I have what you need, it's a small laser level. You should be able to get one from the hardware store.

[Don R]

 I trimmed an aluminum yard stick width wise to fit where I needed it to go. I have a piece of carbon fiber for a straight edge that can flex while maintaining a pretty straight line.

[RAFster122s]

Laser level shoots a line, not a dot...

[Kaze]

Thank you everybody for your help.

I weighed my options, and I decided that buying an offset sprocket for the front was going to cause future b.s. for either me or a future owner. Especially since it's a part that gets replaced now and again. The fact that it cost $100 wasn't happy news, but I was much more concerned about having to chop my aluminum front sprocket cover.

Instead, I bought a used rear sprocket carrier from an older K model (Ebay $30), and then ordered a 10mm spacer from Ken at CycleX ($25). That spacer tidied up the gap on the left side of the axle. Plus he was a cool guy to talk with, so that was good.

The chainguard is my only challenge left on this particular quest. Can no longer install it as Honda intended, because the chain drags on it. If I mount it on the opposite side of the mounting points, it hits my fat-azz tire (K7 wheel).

Going without a chainguard seems like a bad idea, so I think my only option is chopping it...I mean "customizing" it. 4" grinder, here I come...

[PeWe]

Find another chain guard to modify?

[RAFster122s]

Se chose to make their own from section of aluminum L "angle iron" with few brackets and cuts to work instead of cutting up a stock one...

[Kaze]

No, I went ahead and used the one that was already on the bike. Sadly my chain guard was damaged a short time ago by an absent minded geezer who didn't see the big chain locked around the wheel. When "he" (ehem) brought the bike down and forward from the center stand... chrome origami. So I didn't feel particularly hurt cutting the chainguard up a little bit today.

I don't think that they should sell black cloth covered chain locks for wrapping around black tires. Safety orange. On the other hand, I haven't forgotten the lock since then.

If you're not familiar with this specific part, I cut out approximately a foot of material on the right there (photo). Both the inside and outside used to be the same height. Now it doesn't touch my tire or chain. Spinning the wheel I hear nothing but chain. Knock on wood. The "origami" can still be seen toward the left.

Hopefully I don't come back tomorrow with any stories about how my crummy mod job, tripped up my bike and sent me into orbit around Pluto.

[RAFster122s]

Good that Pluto is no longer a planet, eh?

[Kaze]

I was hoping somebody would come back with that.
(Poor Pluto. You'll always be my desolate ball of rock and potential water ice.)

[Kaze]

"L angle iron"... (chuckle) Right family, wrong member.