Topic: 1978 CB750K — Tell me about your 836cc experience

[SKTP]

Disconnected the clutch switch and put it in fear for the first time!

Something weird is going on with the electric starter too...

[MCRider]

Disconnected the clutch switch and put it in fear for the first time!

Something weird is going on with the electric starter too...

"fear" = Freudian slip?

[SKTP]

Ok. It goes, now to make it stop.

I have read and searched ever double disk thread ever and now it's time to actually figure it out...

So I bled the brakes and basically they both appear to be 80-90% on when the lever is not pressed...then on-on when pressed...so the hydraulics are working.

I'm thinking I will unbolt one and see if it spins then the other...I guess figure out the stock one first then attemp to shim or file the new-second brake?

I tried putting a feeler gauge between both and it's crazy tight.

Looks like a lot of trial an error is in my future.

I think I need new bleeder screws. Where did you get your speed bleeders?



Had a pretty good leak until Teflon tape got involved. Goodbye caliper paint!

[Tintop]

Don't press the brake lever with a caliper moved, or the pads will close up on the removed one.  Pain trying to get the piston back.  I have a small piece of metal about same width as a disk I insert into the caliper.  Did you shim the caliper holder?  You can get SS Speed Bleeders to replace the stock ones, no more rust.

[flybox1]

here's what caused my dual disc setup to lock and how i corrected it...
http://forums.sohc4.net/index.php?topic=105018.msg1344173#msg1344173

also, be sure to emory cloth or wire wheel all the paint off the sides of the brake pad backer.  it makes the fit too tight.  brake pad need to move freely without binding when inside caliper

[SKTP]

Thanks flybox1...I need to take a better look at what is really going on with the calipers. The wheel turns, but the brakes are draggin alot for sure...I think I can see the twist when a pull the lever on the "new" non-stock brake

thanks  Tintop...would not have thought of this: I have a small piece of metal about same width as a disk I insert into the caliper. — great idea

flybox, how thick of shims are you talking about? I'm guessing I will be searching out thin washers?

[flybox1]

flybox, how thick of shims are you talking about? I'm guessing I will be searching out thin washers?

I used standard zinc'd M6 and M8 washers @ the caliper arm mounts

[SKTP]

Here's a quick sketch.

So basically I need to put washers on 1,2 and 3, from what I understand...did yours take multiple washers? Any details appreciated...thanks

[Tintop]

The bottom boss is the longest (#3), that is your baseline to true too.  You add shims to #'s 1 & 2.  Should be about 2mm required to get things squared up.  On my 550 I reversed the legs so the calipers are behind the forks.  To get the left (old right side) caliper squared I has 2mm removed from the pivot pin where it contacts the boss.  Got the idea from bwaller.

[flybox1]

The bottom boss is the longest (#3), that is your baseline to true too.  You add shims to #'s 1 & 2.  Should be about 2mm required to get things squared up.  On my 550 I reversed the legs so the calipers are behind the forks.  To get the left (old right side) caliper squared I has 2mm removed from the pivot pin where it contacts the boss.  Got the idea from bwaller.

+1
..for my 750, i did not have to remove any material to get it square.
one trick, is to affix the piston side of the caliper(with the pad inside) to the caliper arm and hold the pad as it would normally rest, against the rotor.  the caliper arm will be in its natural position.
you'll be able to sight down the caliper arm, front to back, to see how the caliper arm pivot mount sits in relation to the fork mount locations (bosses) 
It will show you where and how much to shim at the (2) M6 top mounts and the (1) lower M8 mount.

[SKTP]

Thanks so much guys...this makes way more sense to me now

[Cam]

Ok...more wiring questions:

What are these three and what to they connect to?


And...what are these two and where do they go? The long two; black and pale green?

Hey quick question, in the second picture that long green ground wire; where does it go? I know the light green is horn and the dark green has a smaller female end on it but where does it go? Mine isn't plugged into anything. Also, I saw you were messing with the green/red wires. I've seen a schematic of where all it's supposed to go but I'm still a little confused on it. Mine comes out of the headlight bucket with a ground wire with it and doesn't reach far enough to go anywhere really. Any ideas?

[SKTP]

Well I'm confused.

Added washers to the non-stock side. Had both calipers off and lined up a straight edge to the arms (consisted to the disks) they both now seem identical.

So here's the weird part; the stock side is dragging worse than the new side?

If I loosen off either brake via the 2 large caliper bolts stock side drags new side pretty smooth.

I thoughly cleaned both calipers, there's no pain on the inside surface...do the brakes take some using to brake in?

What should be the next step?

Sorry typed on an iPhone and it's not letting me edit easily

[754]

Pale green and black, are for the horn..

[fendersrule]

First pic: grey and black are for flasher. Green one just hangs by itself.

[Stoli]

That long green wire that runs through the triangle towards the rear doesn't go to anything. My guess is that they had plans for something on the K8 when they designed the harness but decided not to use it.

I think the other questions are from an older post, but FWIW, the green, white, black trio in the first pic are all used by some of the newer flashers. The stock didn't use the green. If you switch to LED winkers, it is easiest to get a new flasher that uses all three, instead of adding a load resistor which would be required to use the stock flasher.

[flybox1]

Well I'm confused.

Added washers to the non-stock side. Had both calipers off and lined up a straight edge to the arms (consisted to the disks) they both now seem identical.

So here's the weird part; the stock side is dragging worse than the new side?

If I loosen off either brake via the 2 large caliper bolts stock side drags new side pretty smooth.

I thoughly cleaned both calipers, there's no pain on the inside surface...do the brakes take some using to brake in?

What should be the next step?

Sorry typed on an iPhone and it's not letting me edit easily

for the stock side, the next step is to get the piston to retract, and set your stationary pad to rotor gap.

[SKTP]

So using the brake adjust ment screw set the stationary pad to sit back? Sorta?

[flybox1]

yeah...one thing to be aware of.  that inside stationary pad 'rocks' in its mount, so it always sits flush with the rotor.  when you 'gap' it you need to get that feeler gauge over as much of the pad surface as you can, not just the edge.

[RAFster122s]

Your photos of the calipers do not show the caliper arm adjustment screw and spring being used. It locates your inboard pad properly to give it a bit of clearance when the brake is not applied. It needs to be there to function properly. The caliper seal will retract the outboard pad to give the needed clearance on the outboard side so the pads aren't dragging.   
Your pads are binding on the rotor and have a misalignment to be 80-90% when sitting but you knew this.  It may require shimming or filing of the caliper legs to get them to work properly to gain the required clearance. Make certain your caliper bottom (closest to the axle) has the same clearance as the top. It is possible you may need to shim the left leg. Usually don't if it was right before you did the rebuild. May have forgotten a shim washer there on reassembly?

[SKTP]

I will double check for washers/spacers...

Right now I have the FORK - then the FENDER MOUNT - then the BRAKE MOUNT...correct? Has to be right, there's no other way?

Is there a front and back to the top brake-mount-holder (#4 below) could that be backwards?

[SKTP]

Drove about 5 miles today...still need to sort out the dragging front brake and the exhaust leak...

...but, the engine sounds great and runs smooth...and it shifts smoothly (replaced the tranny, that's what started this rebuild)

Really happy....almost finished!

[754]

Tried to post friday but had bad wifi..
 Shim. 4 and 9 ...3-4mm. On the nonstock brake side, if you have not already..

[nutsandbolts2013]

I'm new here. Your bike looks very nice. I just finished my build last month. I did a dual disc conversion on my 78 and I had to put small washers between (in the diagram) #8 bracket and the outside caliper #2. Before I did that it rubbed slightly, after the washers, it worked perfectly.

[SKTP]

I had the fender mount between the fork and brake mount?!!!