SOHC.co.uk Forums > CB750
Twin disc caliper modification?
Bryanj:
Correct with pressure but you have to move twice the volume so lever comes farther back. When i twin disced a 500 back in the 70's Girling had just started doing Honda bits so bought a GL1000 one from them
71 V12:
--- Quote from: sprinta on April 21, 2020, 10:17:09 AM ---Thanks for the replies and comments.
With respect to the use of a GL1000 master cylinder. Having only just recently had my original master cylinder re-anodised I would wish to continue using it but clearly if it proved not provide the necessary braking force then I would look to replace it with a GL1000 or similar version.
As indicated, there would appear to be two lengths of the Z900 brake hose, one is the same length as the Honda one and one is slightly longer, see attached. Fortunately the one I had was the longer one. However, the std Honda one may be OK? It depends on how you intend to secure the hose. As I wanted to use the original hose brk I needed a slightly longer hose another type of retention may allow the std Honda hose to be used?
With respect to the GL1000 disc bolts. I think you will find that they are no longer available new, see attached. I bought mine s/h from DK or Two Wheeled Spares on e-bay, see attached,together with the caliper and caliper brks etc. They currently still have a number of sets available. I was fortunate with the the bolts and plate I bought as the bolts were as new and the plate reusable, so you need to look at the photos carefull or ask them to give a condition status before purchase.
--- End quote ---
Hi Andy, I ordered the GL1000 bolts from DK which I received today, and as with you in as new condition 👍👍👍
Do you have a Kawasaki part number or application for the longer brake hose?
Many thanks,
Kevin
sprinta:
--- Quote from: 71 V12 on April 24, 2020, 12:33:05 PM ---
--- Quote from: sprinta on April 21, 2020, 10:17:09 AM ---Thanks for the replies and comments.
With respect to the use of a GL1000 master cylinder. Having only just recently had my original master cylinder re-anodised I would wish to continue using it but clearly if it proved not provide the necessary braking force then I would look to replace it with a GL1000 or similar version.
As indicated, there would appear to be two lengths of the Z900 brake hose, one is the same length as the Honda one and one is slightly longer, see attached. Fortunately the one I had was the longer one. However, the std Honda one may be OK? It depends on how you intend to secure the hose. As I wanted to use the original hose brk I needed a slightly longer hose another type of retention may allow the std Honda hose to be used?
With respect to the GL1000 disc bolts. I think you will find that they are no longer available new, see attached. I bought mine s/h from DK or Two Wheeled Spares on e-bay, see attached,together with the caliper and caliper brks etc. They currently still have a number of sets available. I was fortunate with the the bolts and plate I bought as the bolts were as new and the plate reusable, so you need to look at the photos carefull or ask them to give a condition status before purchase.
--- End quote ---
Hi Andy, I ordered the GL1000 bolts from DK which I received today, and as with you in as new condition 👍👍👍
Do you have a Kawasaki part number or application for the longer brake hose?
Many thanks,
Kevin
--- End quote ---
Hi Kevin
Good that you also managed to get a good set of bolts from DK.
With respect to the longer Kawasaki hose. As indicated there appears to be two possible lengths available. The longer one is around 380mm compared to the shorter one which is around 360mm, which looks to the same length as the std Honda ones?
The Kawasaki code No is: 43059-011 however, I can't advise if that is the longer or shorter version you would need to ask whoever you purchase it from it's length before purchase.
I would also hold back until you decide how you are going to anchor the hose as you may well find that the std Honda one may suffice?
Andy
71 V12:
Hi Andy,
Did you get a chance to ride since the twin disc upgrade?
Interested to know your impression of the brake performance.
Regards,
Kevin
sprinta:
Hi Kevin
I have been a bit amiss by not following up with impression of the twin disc conversion.
I've done around 200 miles on it over the last couple of weeks or so.
The extra weight certainly took me by suprise on the first ride with the extra weight dropping the front into corners quiet noticeably, but I soon got used to it and it now give a sense that the front end is firmly planted to the road.
Yes, the twin disc does make a considerable diffierence and certainly worth it, in my opinion.
As the pads I used were a bit thick I had to reduce their faces and I also bevelled the edge's, perhaps a bit too much as only about 40% of the pads are currently in contact with the disc but even so it is a significant improvement and will clearly improve as more of the pads wear into contact with the disc.
No, they are not in the same league as modern brakes but they are certainly as good as twin disc bikes of the same period such as the Suzuki GT750 and the Kawasaki Z900A4, both of which I own so can comfortably make the comparison.
The std master cylinder works just fine and I can see no reason to go for anything larger, such as the GL 1000 etc.
One thing I have noticed is that the speedo cable runs very close to the outer edge of the disc and after the first run it had cut into the outer plastic covering of the cable. I have overcome this to a degree by packing the cable to the mudguard stay and time will tell as to if this is a satisfactory solution?
So overall I am very happy with the conversion which I have found to improve the the braking, as long as you accept the limitaions of any twin disc setup of that period.
The only down side, as previously expressed, is that it will be necessary to have to remove the whole caliper and brk assy to get the front wheel out, which will hopefully only ever be needed to change the tyre.
Andy
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