Katit's 1978 KZ650 project

Here is caliper piston chart for the classic Kawasaki bikes.

 

wrote:

Here is caliper piston chart for the classic Kawasaki bikes.

 

Man.. This is what I was afraid of. Piston measured 43mm and 41mm long. "Front" of piston has some kind of different material embedded in. None of the pictures with pistons show them in front. And I was kind of thinking 40mm must be it, because 41mm I measured is close enough.

Donor is 650C (1979). Does it mean I am looking at Z650C3 line with 43dia and 41mm long piston?

In reality, I am only worrying that diameter is correct. 1mm of piston length is equal to 1mm in total pads wear, not horrible.

In reality, I am only worrying that diameter is correct. 1mm of piston length is equal to 1mm in total pads wear, not horrible.

If a piston is 34 or 41 mm in length, he move the same way out of the caliper bore. It´s the brake pad and disk thickness that set the piston movment limit.

wrote:

In reality, I am only worrying that diameter is correct. 1mm of piston length is equal to 1mm in total pads wear, not horrible.

If a piston is 34 or 41 mm in length, he move the same way out of the caliper bore. It´s the brake pad and disk thickness that set the piston movment limit.

I was trying to say something different. All it is - it's amount of fluid in caliper. With shorter piston there will be little bit more fluid (just like IF there is 1mm of total pad/disk wear)
Fluid compresses more than metal, so there going to be more "mushiness" in brakes. But again, 1mm will not be felt.

If it was 34 vs 41mm then I would definitely worry. Seems too much for my taste. At this point, there is more chance for piston to "bite" into caliper wall.
 

The material in the hollow cup of the piston is to reduce heat transfer to the fluid and help stop the piston from resonating aka squealing. I think I saw pistons with such material at z-power uk. Not sure of application but if memory serves me I did see them there. 

www.z-power.co.uk/z650/caliper-piston-42mm-1012 . 

Fluid compresses more than metal, so there going to be more "mushiness" in brakes. But again, 1mm will not be felt.

 Fluids are not compressable but the weakest part in the break system are the old rubber break lines. They will age and flexing/expant under pressure in her diameter and give you the "mushiness" feeling. Modern steel braided lines gives you a more precise pressure point and control/feedback to the front brake.

wrote:

Fluid compresses more than metal, so there going to be more "mushiness" in brakes. But again, 1mm will not be felt.

 Fluids are not compressable but the weakest part in the break system are the old rubber break lines. They will age and flexing/expant under pressure in her diameter and give you the "mushiness" feeling. Modern steel braided lines gives you a more precise pressure point and control/feedback to the front brake.

lines expand and it’s biggest factor but fluids do compress

Compressibility
Brake fluids must maintain a low level of compressibility, even with varying temperatures to accommodate different environmental conditions. This is important to ensure consistent brake pedal feel. As compressibility increases, more brake pedal travel is necessary for the same amount of brake caliper piston force.

I think I have a spare front brake caliper.  I can measure the cylinder dia tomorrow.  It's for a D1 model bike.

katit post=869729
Man.. This is what I was afraid of. Piston measured 43mm and 41mm long. "Front" of piston has some kind of different material embedded in. None of the pictures with pistons show them in front. And I was kind of thinking 40mm must be it, because 41mm I measured is close enough.

Donor is 650C (1979). Does it mean I am looking at Z650C3 line with 43dia and 41mm long piston?

The Brakecrafters page says the '79 KZ650C3 used a piston with a 43mm OD and 40mm length. If the piston you have is close to 43mm OD, then this is probably the part you need.

www.brakecrafters.com/collections/1979-k...ess-steel-piston-kit

Here is some more info about calipers. The Z1 (73-75) used a different style caliper. The piston for those is shorter in length.

Many of the 1977 to 1980 models used front calipers that look pretty much the same from the outside, but there are a ton of variations. Some were mounted ahead of the fork, some behind. The bleeder screw and hose mounts moved around. Some had hard line and some used a banjo bolt. And watch out for the shaft model calipers. I think they have a different mounting plate.

While the 77-78 caliper pistons were hollow, some of the 79-80 models included an insulating pad that touched the brake pad backing plate. This was to support the change to sintered metal pads which ran hotter.  The length difference (40mm vs 41mm) shown in Scirocco's chart seems to follow the models that did not have the insulator (40mm) and the models that included the insulator (41mm).  When they switched to the insulator, I believe they also deleted the anti-squeal shim in the front and back.  This shim maybe isn't a full millimeter thick, but removing the shim does help to account for the increased length.

The pistons with insulators are roughly the same overall dimension and will fit. I replaced my '78 rear caliper pistons with the later insulated version, since I was buying new ones anyway from Brakecrafters. They fit fine and work the same as the original ones.

I think the right side caliper with 43mm piston is somewhat hard to find.  Based on Scirocco's chart, it seems like only the '79 KZ650C3 and the 79-80 MKII (A3,A4) and Z1R (D3) got this version.  Scirocco's chart doesn't include the LTD model, but partzilla suggests the 79-80 LTD had it as well (B3, B4).

I just noticed that Brakecrafters does not list any front caliper pistons which include the insulator.  They do have insulator pistons for the rear caliper.  I'm not super happy that they are suggesting the non-insulated style is correct for the 79-80 models.

This site shows a picture of the correct piston for the 79-80 KZ650 and KZ1000 (43020-1012) with the insulator on the end of the piston.

www.z-power.co.uk/caliper-piston-42mm-1012

wrote:

katit post=869729
Man.. This is what I was afraid of. Piston measured 43mm and 41mm long. "Front" of piston has some kind of different material embedded in. None of the pictures with pistons show them in front. And I was kind of thinking 40mm must be it, because 41mm I measured is close enough.

Donor is 650C (1979). Does it mean I am looking at Z650C3 line with 43dia and 41mm long piston?

The Brakecrafters page says the '79 KZ650C3 used a piston with a 43mm OD and 40mm length. If the piston you have is close to 43mm OD, then this is probably the part you need.

www.brakecrafters.com/collections/1979-k...ess-steel-piston-kit

Here is some more info about calipers. The Z1 (73-75) used a different style caliper. The piston for those is shorter in length.

Many of the 1977 to 1980 models used front calipers that look pretty much the same from the outside, but there are a ton of variations. Some were mounted ahead of the fork, some behind. The bleeder screw and hose mounts moved around. Some had hard line and some used a banjo bolt. And watch out for the shaft model calipers. I think they have a different mounting plate.

While the 77-78 caliper pistons were hollow, some of the 79-80 models included an insulating pad that touched the brake pad backing plate. This was to support the change to sintered metal pads which ran hotter.  The length difference (40mm vs 41mm) shown in Scirocco's chart seems to follow the models that did not have the insulator (40mm) and the models that included the insulator (41mm).  When they switched to the insulator, I believe they also deleted the anti-squeal shim in the front and back.  This shim maybe isn't a full millimeter thick, but removing the shim does help to account for the increased length.

The pistons with insulators are roughly the same overall dimension and will fit. I replaced my '78 rear caliper pistons with the later insulated version, since I was buying new ones anyway from Brakecrafters. They fit fine and work the same as the original ones.

I think the right side caliper with 43mm piston is somewhat hard to find.  Based on Scirocco's chart, it seems like only the '79 KZ650C3 and the 79-80 MKII (A3,A4) and Z1R (D3) got this version.  Scirocco's chart doesn't include the LTD model, but partzilla suggests the 79-80 LTD had it as well (B3, B4).

Calipers I use is from 79 KZ650C so it makes sense. I already ordered from Brakecrafters, oh well. Will see what pistons look like, but most likely I will end up using them

What do you think about plastidip for those? They are kind of expensive for what they are. And painting them won't do, it will scratch frame. 

I never used plastidip but sounds like it's exactly what's needed. No?