1980 KZ550LTD Fork on a 1981 KZ550A

Any reason these two forks wouldn't be an OEM match? I have a slightly bent front fork, and am looking for a replacement. Specifically, I'm looking at this one on eBay - it looks pretty clean. tinyurl.com/n89o6jl

I'm brand new to this, and having trouble distinguishing what is the same/ different between the KZ550 sub models and years. I know the LTD frame kicks up in the rear, but I wasn't sure if any of the front end changed as well.

The upper fork tubes (Inner Pipe) & the fork springs might be different lengths.
At Partzilla they have different part numbers; in the diagrams the forks look very similar & do share some parts, though.

Edit: the forks in the tiny url might be from an 81 or 82 GPz 550.

Just check they are 36mm diameter, and not too far out in length. if they are a touch longer you can always drop them further through the top yokes.

Well, I went ahead and ordered it. I'll report back after I receive it and let you guys know. For $35, it was worth risking it. The lower fork tubes are different - there's a mounting location for the second caliper.

I could be wrong, but those forks might not be stock for a 550-Ltd.
I think they're from an 82 GPz550 --- 35mm. ??? Or 81.
I did not click the tiny url the first time around.

Doh! yours is a single front caliper? I'd assumed it was twin disc, I though the USA kz550 had this. Maybe a good time to convert to double disk, or tolerate an empty caliper mount for the time being.

Martin,

81 twinshock GPz550 forks 36mm - like the z550, 650 and 750.
82 unitrack Gpz550 forks 35mm

The later forks were thinner diameter but fatter wall thickness - so said the kawasaki sales blurb of the day.

All right guys, here's the results. I lined up the new fork with the old one.



So the axle receivers are the same size, the caliper mounts are the same location, size and distance, and the fender mounts line up. The lower fork tube is shorter, and the upper fork tube is about 1 3/4" longer. The upper fork tubes are the same diameter. The steering stem is an exact match.

So, in short, this new fork will bolt on with no adjustments whatsoever, but it will be just a touch longer, and the lower fork tubes will look different. It's weird to see what parts are identical between the two, and what parts are just different enough to make you scratch your head.

I have a single front caliper, and I'm going to tolerate the empty mount for the time being. I may switch to dual at some point. Maybe I'll mount something decorative there. Who knows.

I think I'm leaning towards Tyrell Corp's 81 GPz550 since the diameter lines up. I'm not sure which look I like better, but since I'm going cafe racer, the smaller one will probably look better on the bike.

Are you sure the caliper mounts are in the same place relative to the axle? That is often different between dual-disk models and single disk models.

This is some info I collected over the years.

Brake disks, and likely forks, depends on the year and location. There are a slew of different brake diameters for the 400/500/550 line.

The Kawasaki Factory service manual, uses the term "effective disk diameter" for it's measurements, which is not the actual O.D. measurement. From what I gather, "effective disk diameter" is measured from the center of the pad area.

From the factory service manual (red base manual 99924-1018-03):

1979 500B1 models:
Europe and Australia got dual front disks. They were 232mm.
Everywhere else got single disk. It was 250mm.
All had rear disk. It was 237mm.

1980 500B2 was the same 500B1.

The forks have bosses for calipers on both sides even if the bike only came with one brake. But the forks will be different from dual disk models because the disk sizes were different.

1980 400J1 model:
UK and West germany got dual disk 232mm.
Japan and elsewhere was single disk 250mm.
Rear drum.

1980 550A1 models:
Europe got dual disk 232mm.
Elsewhere single 250mm.
Rear drum.

1980 550C1 model:
European got dual disk 226mm.
Elsewhere single 236mm.
Rear drum.

1981 400J2
UK and West German dual disk 226mm.
Elsewhere single 236mm.
Rear drum.

1981 500B3:
All got dual disk 226mm.
Rear is 226mm.



1981 550A2 same as 400J2 single
1981 550C2 same as 400J2 single
1981 550B2 same as 500B3
1981 550D1 same as 500B3 (Actual O.D. is 260mm. Rear is 7mm thick, fronts are 5mm thick.)

The forks use different amounts of oil too.