Fork Seals / Oil Change - Confusion of how much oil to refill

[ChucksKDX]

I've just changed the fork seals and fork oil on my '01 KDX. My manual is confusing because it states under suspension specs 'fork oil capacity' of 623ml (completely dry); however, it states under fork oil change, fork oil capacity when changing oil is 530ml. But I didn't just change the oil, I also changed the fork seals. As well, I didn't do a complete disassembly since I did not disassemble the fork cylinder unit for each. Where does changing fork seals and oil fall in refilling my oil? The manual also mentions a fork oil level to maintain but I don't have anything to measure that with. I was counting on emptying the old oil and refilling; just like I do with my truck, I know exactly how much to put back in. Can anybody tell me the correct amount to refill?

Thanks,
Chuck

[KDXGarage]

You are in bad shape if you can't afford two zip ties!

Don't worry about the volume. Go by level.

Get two zip ties and make a "T" Hang it down in the fork with the springs out. With the springs out and the tubes compressed, measure the distance from the top of the tube to where the top of the oil is on the "T". That is your level. A syringe and tubing is bought from Tractor upply, etc. to remove extra oil. If it is too low, just pour a little in, then remeasure. If you do it too high, then wipe the "T" dry before checking again, as it will just be where it was before.

[ChucksKDX]

Okay thanks. So I'm shooting for 87mm from top of inner tube to oil level; fully compressed w/o spring. I can tell you that I already did 530ml before second guessing myself and when I measured it just now, I'm at 143mm. So roughly 2 inches low still. So sounds like I will end up closer to the dry capacity of 623ml when I get to 87mm. Even though I didn't do a 'full disassembly'. Appreciate the help!

Chuck

[bufftester]

Always go by level, it's much easier to replicate, and easier to adjust when tuning your forks. The zip tie trick works, Motion Pro also makes a fork oil level tool which is basically a long metal straw with mm measurements on it attached to a syringe.

[KDXGarage]

ChucksKDX, you have got it. Do remember to cycle the cartridge rod through the entirety of its stroke several times before taking the measurement. There could be air in there.

You are very welcome. Thanks for asking a suspension question. I do all right on those. :-)

On open cartridge forks, go with level. With closed cartridge forks (2005 - 2008 KX250, 2006+ KX250F, KX450F, KLX450R, etc.), go with volumes.

[ChucksKDX]

Appreciate all the help. I ended up using my digital caliper which worked great to measure the distance from the top of tube to oil level.

Thanks!

[KDXGarage]

DAMNIT, HE's RIGHT! I have a cheapie Harbor Freight one that I could do that with. Great idea! Thanks for sharing.

[kdxdazz]

As stated a vernier caliper works a treat. 623 is the dry capacity, never worry about refill capacity as nobody can know how much of all the old oil the expelled, I will say that a good dose of kerosene, mix it up and empty it is a decent way of cleaning the internals, 83mm seems like not a lot of air gap but I don't know your weight and riding style, I set mine at 130mm but I'm very light and only ride single track

[svboy]

Dont forget that on our forks, fork oil level is our only way to adjust rebound. Lower oil level equals slower rebound, higher levels, faster rebound. Oil level is not an absolute. Experiment.

[KDXGarage]

Oil viscosity can affect rebound.

Also, the rebound valving can be revalved.

[kdxdazz]

Dont forget that on our forks, fork oil level is our only way to adjust rebound. Lower oil level equals slower rebound, higher levels, faster rebound. Oil level is not an absolute. Experiment.

Nope. Not even a little bit correct:)

[svboy]

Could you explain further? I can see kdx garages point. A higher viscosity oil will slow rebound and thinner will speed it up, but have a corresponding impact on compression damping, l think. My point is that altering the air gap will speed up or slow down rebound.

[KDXGarage]

Putting in springs not made for an 8-year old will also ramp up rebound action. :-)

[svboy]

On my 06 my suspension shop has revalved the compression stack and put new seals in the cartridge. I have fitted .42 Racetech springs at the front for my approx 73kg weight. These might be a little heavy but the sag figures of 35mm free sag and 65mm rider sag seem right on the money. I am running 5W Maxima. I cant remember my oil level[as recommended by the suspension shop] but it was a lot lower than factory recommendations. These changes have made huge improvements to the front, being more controlled over rocks and whoops with a lot less diving. Well pleased. Dave Moss,the suspension guru, suggested speeding up rebound to help the front deal even better with off-road terrain. Any suggestions on how to do this would be welcomed.

[KDXGarage]

If you could, please start a new thread instead of jumping into this guy's thread.

Thanks.

That place may have put bushings in the "seal" heads, as there are no seals inside there.