Front fork lower after changing fork oil and seals

Hello,
I recently swapped out some worn seals on my front forks. Also put some new fork oil in it. Per manual I put in 220ccs (wet) into each fork.
I've now reassembled the bike and I'm noticed my front suspension is considerably lower then it was before. The fluid I used was Honda SS-8 10w as it's really the only stuff I can get around here except for honda ss-7 5w. I though the 5w might be to light.
Any advice would be helpful!

Oil grade doesn't effect the height of the suspension, only the damping. The amount of oil only very slightly changes the height. For a properly set-up fork, taking all the oil out altogether will only slightly lower the height (that's because there's less air in there to compress).

If you have air forks, the fork pressure will change the heights. The pressure should be around 5-15psi, wherever feels 'right' for you. You can run higher, but at the risk of leaks. I keep hearing about 'blowing out the seals' if you run too much pressure. But I've only ever seen leaks. Having said all this, if you have air forks, fitting a slightly longer spacer and a slightly thicker oil and keeping them unpressurized is probably the cheapest mod you can do that will significantly improve your suspension.

The next thing to do is to just make sure you reassembled correctly. I don't know what bike you have, but most of them have a spacer in the fork. There should be a small amount of preload when assembling. If there was no preload - if you could put the fork caps on without pushing against the spring - then you either need a spacer if you don't have one, a longer one if you do, or new springs.

ToastRecon wrote: Hello,
I recently swapped out some worn seals on my front forks. Also put some new fork oil in it. Per manual I put in 220ccs (wet) into each fork.
I've now reassembled the bike and I'm noticed my front suspension is considerably lower then it was before. The fluid I used was Honda SS-8 10w as it's really the only stuff I can get around here except for honda ss-7 5w. I though the 5w might be to light.
Any advice would be helpful!

What year and model Harley Davidson is the bike? Or is it a Honda? Believe it or not Kawasaki made KZ models ranging from single cylinder 200cc models up to 6 cylinder 1300cc models. Oddly enough they did not all use the exact same front forks. If you add the bike's exact year and model to your signature line it will always show up there. Ed

Looks like he has an 82 kz550 ltd... Which has air assisted shocks. You need to refill the air.

Funny... i just did the seals on mine last night. I used mobil 1 synthetic 5w20 ( this is about 15w fork oil, couldn't find anything local) and the important bit: I filled the shocks to 14" from the top of the stanchion when fully extended. Always measure the level, not the volume.

650ED it is a n 82 kz550 ltd c3. I'll measure from the top of the forks tonight to make sure the level is correct and try the air assist. (If I recall manual shows 7.5-11 psi 10.5 being factory). If that doesn't work anyone know a good site to buy a larger spacer?

And thanks for the replies/advice

Toast

I have no personal experience but I see guys posting about using PVC pipe. 1 1/2” maybe

How much lower is the front end than before? Approximately a couple of inches or what? Are the forks installed into the triple tree correctly?

If you reinstalled all of the parts in the correct order, then the height of the front end should be the same. I don't think the fork oil is going to affect that, nor the air pressure. The height/length of the forks is determined by the fork springs & spacers. I don't bother checking the air on my 81 KZ650-CSR any more as it's nearly impossible to get them the same & simply checking the pressure releases some of the air & changes the pressure.

I would measure the fork springs & spacers and make sure everything is installed right. The manual should have the standard fork length listed &/or the minimum spec. The spacer length won't be listed & I have no idea how long your spacers should be. As for alternate spacers, I'd guess 3/4" pvc pipe would work. I'm assuming the spacers are 25mm O.D. mine are.

Fork Oil Amount. The fork oil amount you found may not be for a 550C. You may need to check the supplements as the first sections of the FSM are written for the 79 KZ500-B1. Kawasaki manuals cover a range of years & can be kind of convoluted. I would check the 1980 supplement as it covers the 550-C1 and also the 81 & 82 supplements and make sure the amount is for your motorcycle.

martin_csr wrote: If you reinstalled all of the parts in the correct order, then the height of the front end should be the same. I don't think the fork oil is going to affect that, nor the air pressure.

The pressure will raise the front a little. And more so now that these bikes are getting pretty old and have old springs, it's not uncommon for people to increase the air pressure to make up some of the sag in the springs. Not the best way to do it, but people do.

If we say there's about 1 sq inch of cross-section area of the forks, and running at 10psi, that means each fork has 10lbs of force lifting the front up from the pressure. The spring rate on an LTD is quite low - I think around 40lbs/inch. So with 10psi that would raise the front by 1/2". 20psi would raise it by an entire inch.

Regarding spacers, I'm not certain on the kz550 ltd , but I've made some up for my kz750 ltd. I used 25mm galvanised pipe because it seems a bit much of an ask putting almost all of my weight and the motorbike weight onto two pieces of pvc. Having said this, many people have been using pvc so for years without issue.

Like IrishYobbo said, the air will only raise the front end about 1/2" at the most. A lot more than that means something is probably assembled wrong.

On a side note, the topic of oil volume in Kz550 Ltd fork legs have come up quite a few times over the years. The various manuals seem to be in error, but it is not exactly certain what the error is. Volume versus level does not agree and comparing them to other 550 forks even makes things more puzzling. I'm not sure a definitive solution has been arrived at.

Here's a link to some of the discussion, and that discussion has links to other, possibly more relevant discussion. It's quite a rabbit hole. The same dilemma does not exist for other 550 models.

kzrider.com/forum/5-chassis/595286-1982-...rk-oil-level?start=0