Topic: Honda CB750K8 CAFE project (near completion!)

[Flying J]

I use this one from cycle gear.

[MCRider]

Nice, that ought to do it. Much bigger than mine.

[Nortstudio]

I wonder how much a local mechanic would charge to get the chain length?

Do you ever have to change the chain length once you determine the length you want - or is a one shot deal?

[Flying J]

What ever gear set you have will always have the same chain length. But if you add or remove teeth you need to adjust the chain length.

[78CB750CAFE]

You can always use a grinder to grind down the pin and then punch it out

[Tintop]

You can always use a grinder to grind down the pin and then punch it out

+1 that's my method.  I always safety wire the master though, if its not the rivet type.

Nice build, really like your tank, and how the engine came out.  Your friends photos are great.

[2256]

Hey guys....project looks great, I myself just started a '78 k model cafe project and I am also going with BCR tank and seat. Are you moving your oil tank and electrics as well? Benji sent me photos of thier new oil tank that they call a fender mount that looks really cool, it is almost hidden completely by the frame so I had to order one. I will be starting my own thread soon but I will definitely keep an eye on yours. Good luck !!!

[AnthonyMichael]

I didn't know they made that. Please post a picture if you have it.



Also, does anyone know the stock diameter of the forks in mm for the CB750K8?

[Flying J]

35mm

[gnarlycharlie4u]

holy chet. a complete teardown in the first post and a real photographer taking pictures.

effing subscribed. this thread looks promising.

I just yanked my motor yesterday and I'm about to start disassembly.  You've got me thinking that maybe I should clean it up first though.
What degreaser/polish did you use?

[JAG]

Dont know if its been mentioned but what are you going to do with the exhaust?

[gnarlycharlie4u]

As far a chain you just need to get the right length and kind. I think the 750 is a 630 style chain. somebody will chime in.

actually...
the k8 is a 630 but you can convert it to a 530 really easily. (as I believe has been mentioned here already)
All the pre K7 750's had the 530 chain.

From the FAQ on doing the conversion:
http://forums.sohc4.net/index.php?topic=372.msg249900#msg249900

Ok so I just went to the bike shop near me to pick up my day to day bike (they were attempting to reupholster the seat) and talked to the guy about the sprocket. He said that I don't necessarily need to get a new one. He also told me to bring it by so he can check it out. Obviously though I'll be getting a new chain. I just put so much work into the sprocket that getting a new one is annoying.

Just mount it on your wall as a trophy. It'll look sweet.
If you get a new chain you should almost certainly get a new sprocket. Well... front and rear, so 2 new sprockets.

[MCRider]

About new chains and sprockets, consider this. I think that the life of a sprocket is 2 to 3 (maybe 4, but we'll say 3 tops) times the life of a chain. So lets say 2. Now I'll grant if you use used sprockets on a new chain youll decrease the life of the chain, but by how much? Let's say 10% for discussion. Now a chain may be $80+/-, and 2 sprockets may be $80+/-.

So if you defer the sprocket change at chain replacement time, you'll lose $8 on early chain wear, but avoid an unecessary outlay of $80 on sprockets, netting $72. If you are good with your chain/sprocket maintenance, I think you'll see the 3X life of sprockets and assuming 20% rapid chain wear on the 3rd chain you're still even more money ahead. (Savings from 2 cycles added together).

I never changed the sprockets on Phaedrus I in 50,000+ miles and never noticed accelerated chain wear, and I used non-Oring chains. Anecdotal evidence to be sure. Do what makes you feel good, but I don't buy it. (changing sprockets with each chain).

[gnarlycharlie4u]

^that makes sense.
I was thinking from a comfort standpoint, you wouldn't be worrying about grabbing a handfull of throttle and loosing a few teeth on a 30 year old sprocket.
I don't mean to say that new chain requires new sprockets, but in this case if he needs a new chain, he should probably go ahead and spend an extra $60 on new sprockets.

[MCRider]

^that makes sense.
I was thinking from a comfort standpoint, you wouldn't be worrying about grabbing a handfull of throttle and loosing a few teeth on a 30 year old sprocket.

That won't happen. But, in the words of Cheryl Crow: "if it makes you happy..."   

[gnarlycharlie4u]

^that makes sense.
I was thinking from a comfort standpoint, you wouldn't be worrying about grabbing a handfull of throttle and loosing a few teeth on a 30 year old sprocket.

That won't happen. But, in the words of Cheryl Crow: "if it makes you happy..."   

You're right... it'll probably just crack in half like my last one. 0.o

Edit: yes it was an ooooold (probably original) sprocket.

[MCRider]

^that makes sense.
I was thinking from a comfort standpoint, you wouldn't be worrying about grabbing a handfull of throttle and loosing a few teeth on a 30 year old sprocket.

That won't happen. But, in the words of Cheryl Crow: "if it makes you happy..."   

You're right... it'll probably just crack in half like my last one. 0.o

Edit: yes it was an ooooold (probably original) sprocket.

Yikes!  Don't mind me...

[gnarlycharlie4u]

Yikes!  Don't mind me...

haha, luckily nothing terrible came of it. But ever since, I've definitely erred on the side of caution.

On a side note. What chain/sprockets do you all recommend for TwoNoobs' K8
the 630 or 530 setup? What brand?
Any chains / sprockets to avoid?

I know that the 530 has less overall mass so you may pick up a little more horsepower(doubtful)
I'll be doing the 530 chain swap on mine. I'll probably go with JT sprockets and an RK GOLD 530 X-Ring Chain

[climbingaz]

I was sort of suprised to learn my K8 had a 630.  My ZRX has a 630 but it's also putting out about 135 hp and over 85 ft. lb. torque.  You could definitely go down to a 530 on the CB with no ill effect. 

[MCRider]

When converting bikes to fast street or track, we routinely drop a chain size if possible. In the HawkGT world i did it. Can't remember if it was 525 or 530, but dropped it to 520. Noticable improvement in performance.

If you've got to replace parts anyway, cheap horsepower. The 630 is a rotating boat anchor. Gnarly, i think you'll like the improvement.

[gnarlycharlie4u]

When converting bikes to fast street or track, we routinely drop a chain size if possible. In the HawkGT world i did it. Can't remember if it was 525 or 530, but dropped it to 520. Noticable improvement in performance.

If you've got to replace parts anyway, cheap horsepower. The 630 is a rotating boat anchor. Gnarly, i think you'll like the improvement.

so much so that you think I can shoot for over the current gear ratio rather than under? I'd like to be able to cruise at highway speeds without hitting redline. But I really don't want to feel slow.

[MCRider]

When converting bikes to fast street or track, we routinely drop a chain size if possible. In the HawkGT world i did it. Can't remember if it was 525 or 530, but dropped it to 520. Noticable improvement in performance.

If you've got to replace parts anyway, cheap horsepower. The 630 is a rotating boat anchor. Gnarly, i think you'll like the improvement.

so much so that you think I can shoot for over the current gear ratio rather than under? I'd like to be able to cruise at highway speeds without hitting redline. But I really don't want to feel slow.

Hmmm tough call. You're cruising at redline now? I think I'd be happy sticking with the stock gear ratio and enjoy the extra pickup and passing power of the lighter chain/sprockets. 70mph should be what, about 5500rpm? Should be comfortable.

[gnarlycharlie4u]

When converting bikes to fast street or track, we routinely drop a chain size if possible. In the HawkGT world i did it. Can't remember if it was 525 or 530, but dropped it to 520. Noticable improvement in performance.

If you've got to replace parts anyway, cheap horsepower. The 630 is a rotating boat anchor. Gnarly, i think you'll like the improvement.

so much so that you think I can shoot for over the current gear ratio rather than under? I'd like to be able to cruise at highway speeds without hitting redline. But I really don't want to feel slow.

Hmmm tough call. You're cruising at redline now? I think I'd be happy sticking with the stock gear ratio and enjoy the extra pickup and passing power of the lighter chain/sprockets. 70mph should be what, about 5500rpm? Should be comfortable.

No I'm not cruising at redline at the moment but when I get up into the 80mph range I'm pushing it.
Also, the 630 15/41 630 setup has a 2.73 ratio. Closest I could get in a 530 I believe is 18/48 (2.67 ratio).
So should I go up a tooth in the front to 19?
Edit: yes cycle-x makes a 19 tooth front sprocket.

[MCRider]

Gnarly: I don't get your speed/rpm. We all know the K8s are slower ( ) but you should at least be at 100mph at 8,000 rpm (redline). Ideally, more like 105-110.  Its like you haven't shifted into 5th?

Your 17" rear skews things a bit. But 18/48 is the stock gearing for the 530 chain bikes. The 17 would make it a little higher. i run and enjoy a 17/48 with an 18" wheel, which is what your 17" wheel would approximate.

My current project has a 17" wheel and the 18/48 equals a 17/48 on the old stocker 18" wheel. Pretty close anyway, I did the math.

You could go up to the 19 to achieve what you want, but I can't see why. Seems some piece of the puzzle is missing.

[gnarlycharlie4u]

To be quite honest, my speedo doesn't work and I just assumed that everyone around me wasn't going 100.
maaaaybe I should fix that...

But the reason I want to reduce the ratio a bit is because I don't want to go screaming around at 7-8k rpm just to keep from getting run over. I'd like to keep up with traffic for 50 miles without devastating my motor.

I like the idea of a bigger rear wheel though. Maybe I'll stick with the 18/48 and go that route instead.
Where'd you get your 18"?