size of front brake piston kz 400 1978

can anyone tell me the size of the front brake piston in caliper? i need to get a rebuild kit but dont have a clue what size because it is not listed for a kz 400b1 the choices are 42mm and 38mm? any help?Central WI thanks

Cody, look at the area under your' master cyl inboard of the brake line. often bore is cast into body. G

CodyHartleben wrote:

can anyone tell me the size of the front brake piston in caliper? i need to get a rebuild kit but dont have a clue what size because it is not listed for a kz 400b1 the choices are 42mm and 38mm? any help?Central WI thanks

Thinking rebuild kits for master cylinder would include a master cylinder piston with primary and secondary cups (on Kawasaki large fours this would likely be a choice between 14mm or 5/8" size bore).

And rebuild kit for a brake caliper would include only the various rubber bits and not the caliper piston.

Am maybe misinterpreting the question, but if concerned with size of the existing caliper piston, why not just measure it to determine whether it's 42mm or 38mm?

Is it known to which caliper piston dimension the 42mm or 38mm measurement is referring to? Would seem too large to be diameter. Maybe circumference?

What is the parts supply source that's giving the choice between these two different sizes for a caliper rebuild kit on a specific bike?

Good Luck!

well i was looking at z1enterprises.com is there better choices i am waiting on getting A shop manual would it be specified in that?

the prob i am having is that my brakes will not realease and is causes them to rub and make alot of friction i had already taken the whole line system and caliper assembly abart and cleaned it and none of the lines seemed to be pluggged the fluid was pretty brown tho ... it seemed to help a tad but still is locking up and there is just about no movement in the brake lever

thanks

CodyHartleben wrote:

well i was looking at z1enterprises.com is there better choices i am waiting on getting A shop manual would it be specified in that?....

Would follow advice received from Z1Enterprises.

I doubt the shop manual will provide dimensions of the caliper piston. Could just measure it.

Kawasaki.com parts diagram shows the same caliper piston being common to six models (including three 1978 KZ400 models). Dimensions aren't shown. Looks like 4 round rubber seals are used in the caliper (including two larger seals for the piston).

A caliper rebuild kit may be available from Z1E, but I don't see it listed. Perhaps via special order, or reference to an alternate source.

However, Z1E does list a rebuild kit for the master cylinder.

At bottom of m/c reservoir, there are two orifices (holes) connecting to the piston bore. The larger hole is the fluid supply port. The tiny hole is a relief port which must be clear to allow the brake to relax after using it. Am thinking a clogged m/c relief port may be causing the brake to drag.

Good Luck!

Cody, you may find this site usefull for info, www.cmsnl.com/ but as the Man says, you're best to measure it and I'll tell you why.
My 500 appeared to have the correct calippers on it.
I bought replacement pistons and seals only to find they didnt fit.
Turns out the calippers are from a 78 650.
Works and looks great now.
Yep, 42 and 38.
edit: part number for 38mm piston fluid seal is
43049-1097
The four round seals that Patton refers to are the o rings that sit on the calipper rails.Mine are 10.1mm internal diameter thickness 1.7 I think.You also have a piston fluid seal and piston dust seal[mine comes in two pieces[rubber and metal]].Yoy'll need the proper grease to re assemble.There are also 4 shaft dust boots in there.

Here's info about 1978 KZ400-B1 front brake as shown on kawasaki.com:

#4 caliper assembly part#43041-1003 common to:
KZ400-B1 (1978)
KZ400-B2 (1979)

#12 piston part#43048-005 common to:
KZ400-A1 (1977)
KZ400-A2 (1978)
KZ400-B1 (1978)
KZ400-B2 (1979)
KZ400-D3 (1976)
KZ400-D4 (1977)



Ref Part# Description Quantity
1 92007-044 BOLT,HEX HEAD,10X57 2
2 461F1000 WASHER SPRING 10MM 2
3 410B1000 WASHER PLAIN 10MM 2
4 43041-1003 CALIPER ASSY 1
5 43057-004 CAP,BREEDER 1
6 43056-004 BREEDER 1
7 43049-1001 SEAL, FRICTION 2
8 92022-1161 WASHER SET,LOCK 1
9 92022-1161 WASHER SET,LOCK 1
10 43049-004 RING,PISTON SEAL 1
11 43083-002 SEAL 1
12 43048-005 PISTON,CALIPER 1
13 92081-1031 SPRING 2
14 92037-1066 CLIP,PAD INNER 1
15 43050-5004 PAD SET 1
16 92037-1004 CLIP,PAD,OUTER 1
17 41080-1001 DISC.PLATE 1

Good Luck!