Topic: Yet another Dual Disks conversion question for a K1

[DesertKyorugi]

I was test fitting my right-side brake caliper holder and is a little concerned that I may need 14mm spacers instead of 6mm spacers that I have been reading from other people's conversions. That is quite a ways off.
Did I miss something?

[Rookster]

You have to file down the lower boss on the caliper bracket to move it closer to the fork leg.  Here is a picture of one I did.



Scott

[DesertKyorugi]

Thank you! That's what I was thinking. I think I can get about 3mm+ off the lower boss and get the gap down to about 9mm

[HondaMan]

It's interesting this filing-off business: I did mine (until 1980 when I took it off) with the stock bracket and 12mm stack of washers! 

The pucks should attack the disk at a slight tilt: this helps to slough off the water and debris constantly to improve the braking when wet or dirty.

[DesertKyorugi]

It's interesting this filing-off business: I did mine (until 1980 when I took it off) with the stock bracket and 12mm stack of washers! 

The pucks should attack the disk at a slight tilt: this helps to slough off the water and debris constantly to improve the braking when wet or dirty.

The left side is closer to the fork and I was just thinking about making it more even 

[HondaMan]

It's interesting this filing-off business: I did mine (until 1980 when I took it off) with the stock bracket and 12mm stack of washers! 

The pucks should attack the disk at a slight tilt: this helps to slough off the water and debris constantly to improve the braking when wet or dirty.

The left side is closer to the fork and I was just thinking about making it more even 

Yeah, I sure can't say that mine looked "even". Many other 750 riders would make mention of that when they saw mine!

[DesertKyorugi]

I think I am going to leave this one alone and see how it is. Will try filing the lower boss on the JDM K1.

[38rudge]

I was test fitting my right-side brake caliper holder and is a little concerned that I may need 14mm spacers instead of 6mm spacers that I have been reading from other people's conversions. That is quite a ways off.
Did I miss something?

You can follow what I did on this link: http://www.sohc.co.uk/index.php/topic,21171.0.html

Yes you do need spacers wider than 6mm, that is what would be required for the later caliper carriers. The amount varies slightly from bike to bike. I do not recommend filling the fork leg boss. Simply use some 8mm washers until you get the correct alignment and then get some spacers made the same width.

[Rookster]

You never file the fork leg boss only the bracket.  It is not about looks.  You need to get the caliper arm in the correct position over the disk so the pads are perpendicular to the disk.  This requires removing material from the bracket's lower mounting boss.  The early C type bracket is different than the later T type bracket.  If you mock everything up and compare the left side to the right side you will see what needs to happen and why the bracket has to move closer to the fork leg.

Scott

[38rudge]

You never file the fork leg boss only the bracket.  It is not about looks.  You need to get the caliper arm in the correct position over the disk so the pads are perpendicular to the disk.  This requires removing material from the bracket's lower mounting boss.  The early C type bracket is different than the later T type bracket.  If you mock everything up and compare the left side to the right side you will see what needs to happen and why the bracket has to move closer to the fork leg.

Scott

In my case I found that it was not necessary to remove anything from lower brk boss. The assy aligned up perfectly only requiring the the top two bosses to be packed out as necessary so when all three brk bolts were tightened the caliper arm and pads aligned perpendicular to the disc. Perhaps this was because I have the original RH fork leg? If it has been replaced at some time in it's life the mounting bosses widths may have changed?

[Rookster]

I just looked at your pictures and your C bracket has already been modified.  The lower mounting boss on a stock bracket extends past the lower holder for the pin.  Yours has been filed.  You can see the file marks on the surface.

Your Bracket:


Stock Bracket:


Scott

[754]

Not sure but I think there is 2 fitting scenarios.
 One for calipers to the front, and different for mounting them facing to rear.,
Is that not correct ?

[38rudge]

I just looked at your pictures and your C bracket has already been modified.  The lower mounting boss on a stock bracket extends past the lower holder for the pin.  Yours has been filed.  You can see the file marks on the surface.

Your Bracket:


Stock Bracket:


Scott

Yes the bottom brk boss does have some file marks.

When I first started fitting the 'C' brk like many before I had read several of the previous conversions, where it was indicated that it was necessary to file either the 'C' brk or the fork leg boss. So in my enthusiasm I removed about 1 mm off the face of the bottom boss only to find that when I came to align the caliper and disc pads the assy was slightly out, in my case. Therefore, by replacing the amount that I had removed by a M8 washer of 1 mm the correct alignment was achieved, see attached.

That is why I have advised that it is not necessary, or in my case it was not, to remove any material from the 'C' brk lower boss. So before you start removing any material from either the 'C' brk or fork leg try fitting the assy and see how perpendicular the disc pads are to the disc. You will probably also find when viewed from above that the caliper arm will not be directly parallel to the disc but sightly towed to the outside as the LH one does, see attached.

Also you need to remember that both pads sit on spherical contact surfaces and as such they will take up any slight non totally perpendicular alignment.

In my case the top rear spacer was made up of two parts as I made a brk to hold the modified hydraulic hose support brk.

I can only report my own findings, which I trust may help. But each conversions seems to require individual tweeks.

[38rudge]

It's interesting this filing-off business: I did mine (until 1980 when I took it off) with the stock bracket and 12mm stack of washers! 

The pucks should attack the disk at a slight tilt: this helps to slough off the water and debris constantly to improve the braking when wet or dirty.

The left side is closer to the fork and I was just thinking about making it more even 

You need to remember that the RH disc mounts around 3mm closer to the hub center than the LH one does. You also need to align the caliper to the disc.

If you bring the 'C' brk too close to the fork leg the pivot point of the caliper arm will be moved such that the caliper arm may well be at the wrong angle for correct operation unless you then also space the disc out as well?

[DesertKyorugi]

Wow, this thread exploded. Thank you @38rudge and @Rookster for all the helpful info and pics. I acutally got up this morning and went to grind the lower boss down(braket) before checking the post. I am glad I did it correctly so far 

I will take more pics later and share it here, gotta get some lunch in me first. I think I took 5mm off and it is now even on both sides as far as the brake caliper mounting point.