EASY FORK OIL CHANGE??

[GOT WOODS?]

Hi Guys,

Getting ready to do some major maintenance on my 03 220 and I'm reading up on changing the fork oil....WHAT THE HECK?!?! Do you really have to go through taking the forks apart to change the oil? Took a long hiatus from riding but on the 20-25 bikes I've owned that ranged from a late 60's scooter (which was the perfect bike to learn trail riding on: LEARN TO RIDE CORRECTLY OR DIE!) to early 2000's ultra street crotch rocket (which scared the crap out of me more than once: LEARN TO SLOW DOWN OR DIE!) I've never seen a more complicated procedure for changing fork oil! Is there an easier way? Does anyone have a good hack to make this easier? I want to mess around with my suspension this year but having to pull these things apart every time I want to experiment with fork oil weight and quantity isn't gonna play well with my lack of free time available to me. Back in the day we took out the screw at the bottom of the fork leg and pumped the old gruel out and put in the correct amount of new fluid. Has anyone modified their forks to allow this to be done with the KDX forks? Drill a hole at the bottom of the fork leg, tap and install a screw? Turn a 2 hour job into a 20 minute job?

Life is complicated enough, fork oil shouldn't be....

SEND HELP!!!!

[KDXGarage]

Those old forks you had a drain screw for did not suffer the consequences of tiny particles clogging valving. Getting most of the old oil out and some of the contaminants was considered good enough back then. Welcome to the late 80's and cartridge forks. Even if you did install a drain screw, you are not going to get all the gunk out of the forks with just a drain screw. Hopefully, you can commit to taking the forks off and emptying most of the gunk out by taking the caps off. Pump the tubes to get some more out. Check the new oil level according to the manual.

Skip the " I want to experiment with fork oil weight and quantity" desire and just go with a known excellent fork oil in 5 weight. Cartridge forks are not going to change much with oil weight. Start with a low oil level and go up if you need to. The correct rate springs are going to be the biggest help for stock 1995+ forks. Beyond that, you can get a Race Tech Gold Valve system to replace the stock compression valving.

The forks are similar to the forks that came out in 1987 for the 1988 KX lineup. They are 37 years ago technology. Even if the 2003 KDX220R came with state of the art forks, they would now be 22 years old technology.

Look up dual chamber forks, midvalves, rebound valving, etc. if you want to dig into even more modern fork technology. :-)

If you feel real froggy, when you work on them, take the springs out and clean them as they will have metal gunk on them. The same gunk that is resting down in the bottom of the forks where a simple dump and fill just won't get it all out.

If the forks have never been serviced, then consider new inner and outer bushings, oil seals and dust seals. If they have the original bushings, then they could be quite worn by now.

I used to work on KDX suspension a long time ago. Here's a pic of some 1995+ KDX forks (1996) that I had apart back then.

1996KDX200Forks.jpg (49.28 KiB) Viewed 2991 times

[kdxdazz]

as usual i will give a somewhat alternative view, my kdx220sr has an oil removal screw as can be seen in the photos, the kdx220r has the exact same boss that i think could be drilled and tapped to except a drain screw, but something worth noting is the kdx220sr is not a cartridge fork arrangement so bleeding the air out of the system will be some what different although not impossible

in regards to choosing an oil weight you cannot just choose a quality 5w as every 5w oil will be different, some examples, the orginal kyb 5w fork oil is more similar to a motul 2.5w, i just did a rebuild on a set of drz250 forks and i viscosity checked the original oil which was very thin, again similar to the kyb fork oil, i compared this to a penrite 5w fork oil which was so thick it wouldn't even flow through the viscosity checker.
you can make a viscosity checker from a simple deodarant bottle lid with a hole in the bottom and then use a timer to let it flow through, always make sure the oils are the same temperature. this also applies to the rear shock, kyb shock oil is much thinner than even motul 2.5w fork oil but i use redline like water which is a 0W but very close to the kyb shock oil

[KDXGarage]

Wow. Interesting. Thanks for pointing it out. Photo from Impex:

[bufftester]

On the original forks oil weight is going to make the smaller change of the variables you can control. The biggest bang for your buck without any doubt is the correct fork springs for your riding weight. It is the single best thing you can do to improve your bikes handling.
As kdxdazz said, different manufacturers oils will differ from one another. I would find what's available in your area and pick one that offers multiple weights to choose from. Keep in mind that while a heavier oil will give you more damping force, that will affect the operation across the entire stroke and all quadrants (high/low compression, high/low rebound).
After getting the right springs, and then finding a viscosity that works for the majority of your ride envelope then valving will get you dialed in. The difference between valving and weight is that you can tune the valving to specific characteristics using a given oil, where just a weight change affects all the characteristics. For most folks though, valving is a bit of black magic, and involves complete disassembly whereas changing oil is easy and quick and only requires you to take off the front wheel and drop the forks out, uncap and drain.

[KDXGarage]

Don't forget to bleed the cartridge, so the level is correct.

[GOT WOODS?]

Thanks guys, but now I'm depressed.... looks like I'm doing a deep-dive into the forks. As it happens, I found out the right fork leg has leaked some oil so I added new fork seals to my list going off to RMATV. Speaking off, I sent my order into RMATV mid-day Friday and got my small parts on Sunday and my tires showed up today. Crazy good turnaround.

KDXGarage: That picture was painful to look at! I'm the kind of guy that takes extensive pics as I'm ripping things apart so when I forget how everything went together I have a backup brain in my camera. I'm figuring 40-50 pics for that jumble of parts.... looks like a Grainger catalogue...

Kdxdazz: Crazy that 5 weight oil can vary so much. I always thought that the number was a constant throughout all of the oils, that's why it got assigned the number in the first place. I learned something new today! Thanks!

Bufftester: I'm considering getting fork springs. I'm 6'-3" and clock in at 190lbs without my extensive gear. Looking at the charts the stocks are not doing me any favors. Thinking that if I can get an electric start on this thing I'm going to do a fork swap at some point so I might just hold off on the springs for now. The only fork mods I ever did was back in my penniless youth on my 1972 LT2 Yamaha 100. The fork springs were sagged out so I found a wood dowel kicking around the garage, sawed it into two pieces, stuffed them on top of my springs and screwed the caps back on. Worked.., sort of... I always wondered what the next owner thought when he pulled those forks apart.... Maybe he followed my lead and got some longer dowels....

THANKS GUYS!!!

[KDXGarage]

You don't have to COMPLETELY disassemble them to just do a complete oil change. That pic is everything taken apart except the rebound end on the rod. There are 10 washers that are about 0.10 mm if I am remembering correctly on the thickness. They stack together. Anything clogging them open can effect damping. I once opened a set of KX forks that had a sliver of plastic jamming it open. No wood, just plastic. :-)