1982 KZ550 Ltd fork oil level

A buddy of mine got a free non-working 1982 KZ550 Ltd. I agreed to bring it back to life, but I ran into a problem when I was rebuilding the front forks. According to the service manual a completely dry fork leg requires ~290 cc (9.8 floz) of fluid (pg 295). The oil level check is 356 +/- 4mm (~14") from the top of the extended tube. I tore everything down & cleaned it up, however, when I put in the right amount of fluid the measured level in the extended fork with no spring is 107mm (4 1/4") low!

I did a rough estimate of what it would take to get to the right level per dipstick and I would have to add approximately 71 ml (2.4 floz). I downloaded a 3rd party manual and it said the same as the Kawi manual. I also did a regular search to see if someone else ran into this and didn't find anything.

So, I'm stuck. I'm worried about blowing out the seals if adding 2.4 floz more is excessive, but I also don't want to have too little fluid, making the front end spongy. Does anyone have experience with this?

Do you have any pics of the forks (especially the tops and the axle mount area)? I wonder if it's possible that sometime in the bike's life someone swapped the original forks for some other forks. Ed

The OD is ~1.41" and the ID is ~1.14 (though my calipers wouldn't reach the innermost land, so it's probably a little less). This is a bike with less than 9k miles from the dad of another guy we know. He parked it for years because it had some issue & he's not a mechanical guy. It's still the dual Schrader valve setup too, but if the pics might still help, let me know. thanks.

If it still has the Schrader valve setup and has the leading axle, plus you know the history of it the fork is probably original to the bike. Ed

So you've never heard of an error in the manual for the "dipstick" measured level & the recommended dry fork volume added for this particular bike? I wish I had a rule of thumb like "the fluid shouldn't be above this part", or something, but all I've ever done with forks is pull them apart, clean them, put in whatever the fluid the manual recommends, and call it good.

GTO6T6 wrote: ...1982 KZ550 Ltd...According to the service manual a completely dry fork leg requires ~290 cc (9.8 floz) of fluid (pg 295). The oil level check is 356 +/- 4mm (~14") from the top of the extended tube. I tore everything down & cleaned it up, however, when I put in the right amount of fluid the measured level in the extended fork with no spring is 107mm (4 1/4") low!...would have to add approximately 71 ml (2.4 floz). I downloaded a 3rd party manual and it said the same as the Kawi manual,,,I'm worried about blowing out the seals if adding 2.4 floz more is excessive, but I also don't want to have too little fluid, making the front end spongy....

Presupposing correct assembly and proper volume measurement, the resulting level is indeed puzzling, at least if the information in the manuals is correct.

The KZ550C LTD forks are different from the other non-C/LTD models, but this of course doesn't explain the discrepancy.



Good Fortune!

On my KZ650-C1 the volume of oil in the manual was a little low but much closer to the dipstick measurement than yours.

I checked my electronic version of the KZ550 manual and it shows the same specs as you stated. I assume you measured the volume very carefully. Did you do both forks legs and was the problem the same in both? I saw that they say to measure with the spring out, but I wonder if they measured with the spring in when the developed the dipstick spec. If you install the spring does the fluid come up to 356mm? Ed

The measurement is done with no springs. But you have to pump the fork sliders a bit to get the oil circulated.

If you measure 107mm from the top, then the oil level is too high, though, not too low.

He's saying the fork oil level is low by 107mm, so his measurement is apparently 463mm from the top of the tube to the oil (356 + 107).

For comparative purposes, the forks on my 81 KZ650-CSR are similar to the 550Ltd's ---- leading axle type with 36mm upper fork tubes (see specifications below).

Fork oil = 270 cc oil change & 291 cc +/- 4 cc dry (rebuild: I added 295 cc).
Fork oil level measurement = 433 mm +/- 4 mm (without springs & forks extended).
Forks = 34-7/8" long --- extended & w fork caps removed (my measurement --- not in manual).
Free spring length - service limit = 497mm (mine measured ~510mm).

Two different manuals:

martin_csr wrote: He's saying the fork oil level is low by 107mm, so his measurement is apparently 463mm from the top of the tube to the oil (356 + 107).

Ok, I got ya.

Then yes, it seems odd that he's that far off.
And it seems odd to me. Since the LTD fork tubes are longer, I would have expected the oil level should be farther from the top, rather than closer, as the manual indicates. I've never done LTD forks, that I can recall, so maybe both manuals are wrong, or the third party one just copied the FSM.

I did the 2nd fork tonight, carefully measured out 290cc of 10w fork oil, and the dipstick level was the same as the first. Both forks are assembled with the piston and cylinder unit inside the inner tube and the inner tube inside the outer one, just like the ones on my 80's Hondas.

I put the springs in & the caps just to see how the forks acted. If I leaned on the sealed fork slowly (not pumping it up), I could compress it around 3.5" (I'm 160lbs). Both were the same. Some non-air assist CB600F2 41mm forks I have on hand only compressed 2 inches, but that might not be the best comparison.

I haven't tried adding air yet because I haven't looked into the best/easiest way to do that. The forks seem spongy, but maybe the air would firm things up enough? The Front Fork Load/Compression Stroke Relationship chart posted above would seem to indicate that. I just don't know what's typical for these forks.

Thanks for the posts so far.