How much fork oil in a 2002 KTM 400 SX

I would expect it to be in the user manual, links attaghed:

KTM 65 MANUAL KTM PDF Manuals Judd Racing Youth Motocross Parts

KTM 65 SX 2015 Downloads

OWNERS MANUALS CATALOGUES

the SX forks really should be taken to a suspension tech to get the inner chamber properly bleed out.
You never just add a cc amount because there is usually some left inside. You bleed out the air and fill. once no more air is coming out you set the fluid level on the outter chamber 110mm to 120mm with the spring out and the fork collapsed.

Thank you for contacting FixYa with your inquiry.
The KTM factory suggested Oil is 1200cc of 10W-40.
http://dirtbike.off-road.com/dirtbike/review/ultraserious-racing-four-strokes-ktm-520-sx-520-exc-400-sx-and-400-exc-20704.html
If we can be of further service please let us know.
Best regards,
TF

It will be written on the side of the engine in ml .

As in 150ml or 200ml . its usually near the filler cap/ dip stick

good luck

Seats changed in 2003. So i think you'll be looking for a 4 stroke ktm between '98 and '02. Ebay is an easy route to go, or you can order a new foam and cover from Moose or Enduro Engineering and rebuild your own seat.

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I recommend sending them out, or get a factory manual. You need fork seal drivers (The correct size) and a solid mechanical background with some good tools. They ar not a simple deal. If you feel comfortable in trying it, get a good manual, and it will walk you through it.

The owners manual says to do the following if you don't want to remove the forks:
*raise the front wheel
*remove the fender, meter cable & unit, headlight, handle bar, fork protectors
*loosen the fork upper clamp bolts
*remove the caps from the top of the fork tube
*fully compress the fork tube so the dust cover touches the bottom and place a stand to hold it
*remove the springs
*set the oil level 68mm (standard) or 60 - 90 mm (adjustable) from the top of the tube

It may be easier to remove the tubes and you could replace the leaky seal at the same time. I did this recently and put in new springs too. It was my first time working on forks. With help from TT members and the service manual it was fairly easy. I didn't buy an oil gauge, seal driver, or spring holder. I used a ruler to measure the oil and a medicine dropper to remove any excess. For a seal driver I used a piece of PVC pipe cut in half then secured around the lower tube to drive the seal. Try a search on replacing fork seals for more info. 5w oil is standard but i have heard that 7 works well Good luck.

Does it have a bad fork seal? Check this by popping the dust cover off the lower legs and if you see fork oil on top of the seal than it has gone dad and needs replaced. Adding oil to the forks will stiffen then back up but if you have bad seals then you will be adding more oil again in a very short time and also this is dangerous cause the oil can get on the brake pads and cause brake fade when you need them.
Good luck.

If you get the sevice manual or contact a dealer to get the correct oil amount for your bike, they need to know the model and year, you have to have the forks off the bike. take the fork caps off, take the springs out compress the upper fork tube all the way and add the specified oil. if they also give you the measured amount from the top that's the best way to get both fork oil levels exact. there is a special tool that you set the oil level in millimeters and it sucks out the oil to the right level, but before you do that step after adding the oil always pull and push on the cartage rod several times to remove air from the cartage tube. you will hear the air coming out and you will feel the changes in the cartage rod as the cartage tube fills up with oil and the air is removed.
something i'm confussed on though is if you replaced a seal you would have had to brake down the fork to replace it. you would have poored the oil into a container, cleaned all the internal parts,and used a fork seal driver to install the new seal. part of your question asks where do i put the oil in? thats in the open end of the fork after you have taken off the fork cap. It sounds to me like you only replaced the dust seal on one fork. that is not going to fix your leaking fork. you need to replace the oil seal thats pressed inside of the top fork tube.