Topic: 72 750 front disc upgrade not helping

[scottly]

A thought just came to mind, did you bleed the master cylinder at the banjo bolt(just as you would if it were a bleeder valve)before bleeding the caliper?

He stated the lever was firm, so trapped air isn't the problem.

[newday777]

A thought just came to mind, did you bleed the master cylinder at the banjo bolt(just as you would if it were a bleeder valve)before bleeding the caliper?

He stated the lever was firm, so trapped air isn't the problem.

Let him answer it

[dave500]

i used a generic 12.5mm one,has a mirror thread though,looks like a yammy dirt bike one?,once i used vesrah rear shoes in my 500,they may aswell of been made of ice,they just did not work even standing on the pedal,i bought genuine honda and boy they work well!

[scottly]

My best guess is that the off-set of the aftermarket rotor is incorrect...

[gmet]

The rotor i purchased was made for a 77 cb 750? and the OD of the rotor was a few mm larger then the earlier CB units so I had the OD taken down slightly to allow the use of my OEM caliper.  Yes everything has been thoroughly bled. Are you guys buying direct from honda oem pads, and will that make a big difference?

Thanks for the pic of your 12.5mm MC as well, I appreciate that ( Dave 500)

[Bodi]

I don't understand this "bedding in" theory. How is it done? Why would a new pad set need it?
I know that drum brakes do need the drum and shoe radii matched and I've done that several times to have optimum braking. I've opened single leading shoe brakes where the trailing shoe has half its surface untouched and only the middle worn at all (because they were never radiused) while the leading shoe was well over half worn out.
But OEM Honda discs? Scrub the disc, bung in the new pads, adjust the dead side gap, and off you go (Hmmm... off you stop?). How do you "bed in" a flat shoe face to a flat disc surface?

Sorry no theory on the original issue. Cast iron disc should be better than OEM SS. Look like #$%*e with rust pretty quickly but provide stronger braking.
Something simple is wrong IMO.

[MauiK3]

I'm thinking the MC is not working properly or there is a problem down at the caliper. Stuck puck or piston?

[gmet]

The caliper was opened up and cleaned out, shined up and a new piston installed, no binding there. I'm suspecting the MC may be the culprit? I'll keep yall posted with what I find.
Thanks

[scottly]

The rotor i purchased was made for a 77 cb 750? and the OD of the rotor was a few mm larger then the earlier CB units so I had the OD taken down slightly to allow the use of my OEM caliper.

All of the 750 rotors are the same 298mm diameter, except the F2/F3, which are 278mm.

[scottly]

Is the rotor bolted onto the carrier backwards? The relieved area in the center faces out on the stock rotor, not in like yours appears to be. Also, what model pads are you using? The early pads have a full circle of friction material, while the late model pads have a flat edge on top. The early pads cover more of the rotor, closer to the center, than the late pads. In this pic, the pad on the left is for the early finned caliper, while the pad on the right is for the F0/F1 K7/K8 smooth caliper.

[gmet]

Gosh, I'll have to see o
how mine is bolted on. So this would offset it more to the left or right I assume? I'm pretty sure I adjusted the gap on the caliper arm correctly but I will go out now and take a look at it. I'm pretty sure I have the full circle pads as well. If the caliper is adjusted correctly would the offset one way or the other matter? Just wondering theoretically.  Good catch though on the picture

[scottly]

Take a pic looking straight down on the caliper, and one from the side. Also, leave the adjuster screw and spring off, at least for now.

[gmet]

sorry, just uploaded these pics without undoing anything. Looks like the disc should be centered better in the slot? Moving the disc to the other side of the carrier maybe?
Right now there is very little of the master puck showing but alot of the slave puck is showing, could that make a difference as well?

[scottly]

I can't tell from those pics. Looking down on the caliper, is it parallel with the rotor, or at an angle? The rotor needs to be flipped, but still mounted to the same side of the carrier.

[gmet]

gotcha, I'll get it flipped and check to see if its parallel with the disc.

[scottly]

It looks like the wear pattern on the back side of the rotor is much wider than on the outside, like I would expect with the early full round brake pad??

[gmet]

Ok, I pulled the front wheel off and checked the rotor to see if it was on the carrier in the proper position and the way its machined makes it only fit one way so my offset has not changed.  I pulled the caliper apart, recleaned the bore, sanded down the paint on the sides of the puck backing plate so it slides freely in the bore, added a touch of grease on the sides of the bore. Beveled the edges of both pucks and finally resanded them on a belt sander with 180 grit. 
Took it for a spin and no change whatsoever.  You have to grab a huge fistful of lever to lock it on grass!
The piston and pad moves easily in and out of the bore but I pulled it apart after I got back and noticed that theres only a small amount of contact in the very middle of both pucks.

[grcamna2]

Ok, I pulled the front wheel off and checked the rotor to see if it was on the carrier in the proper position and the way its machined makes it only fit one way so my offset has not changed.  I pulled the caliper apart, recleaned the bore, sanded down the paint on the sides of the puck backing plate so it slides freely in the bore, added a touch of grease on the sides of the bore. Beveled the edges of both pucks and finally resanded them on a belt sander with 180 grit. 
Took it for a spin and no change whatsoever.  You have to grab a huge fistful of lever to lock it on grass!
The piston and pad moves easily in and out of the bore but I pulled it apart after I got back and noticed that theres only a small amount of contact in the very middle of both pucks.

I viewed the first picture(good pics)you uploaded and it looks to me like the caliper bracket is crooked/off-center.
Does the caliper bracket mount to your fork flush/flat ?

[dave500]

try and find sintered pads?those look like junk?

[RAFster122s]

I think EBC V pads are sintered...

Wonder if they have been brake fluid contaminated previously?

[gmet]

pretty sure they are sintered? If you look at one of the pics you can see that they look  that way. They are new and have had no contamination. As you can see the pads now only have a small area of contact in the center. I sanded these down on a belt sander thinking I was getting them flat but I guess not? Any particular way to achieve this? I searched "bedding" and read up on what I could find but dont think thats my issue.

Dave- I have tried to pm you and scottly but nothing gets sent on my end, any ideas?

Thanks again

[RAFster122s]

Sand by hand on a flat surface with coarse sandpaper. Tape the sandpaper to the surface. Problem is if you introduce a bevel or angle it will be bad...
It definitely is the lack of the brake pads not being bedded in flat with the surface. The area of pad working is the size of two quarters...tiny surface area!

[Tracksnblades1]

This may cover your bedding questions..

It’s like butt holes, everyone has one, as well as opinions.

Don’t over do it. You can smoke the pads too…

[grcamna2]

This may cover your bedding questions..

It’s like butt holes, everyone has one, as well as opinions.

Don’t over do it. You can smoke the pads too…

Lol 

[Don R]

 I did the double piston caliper swap on my gl1000 with 2 32mm calipers from a V65 I used the kevlar ebc pads, they took a long time to see an improvement but it was worthwhile. I may still look for Honda pads.