I changed the fork seals but i dont know how much fork oil to put back in fork tubes bike didnt come with a owners manual im having trouble finding repair manual

1985 YZ250N, With the Fork off, Cap off, Spring out, take a clear school plastic ruler pore in 5W synthetic fork oil till it's 135mm from the top with the fork tube all the way down, till it just touches the ruler and the 135mm mark. Reinstall the spring, pacer, washer, Damping rod to cap, and install back in the clamps. I raced this bike for 18months in 1985/1986. Change the seals when they leak and toss the 38Kg Fork springs for 41Kg + springs to your riding weight. Over all was a good fork for it's time and Race tech can rebuild the fork and shock to your riding style and you're riding weight. I Miss the Fork flex on hard landings to my other New bikes. I still ride and Race the 85,YZ490 with the same fork.

If, notice I said "if", your bike has the standard 41mm wide glide front end, changing the fork seals is not that difficult.

Get the bike up off the ground on a stable lift. Safety is paramount.

Now take the front wheel and fender off. Take the large "Bolt" out of one of the fork tubes at the upper triple tree. There are special sockets made to do this with so that you won't scratch your chrome upper tree. Loosen the pinch bolt on the lower triple tree. Put some lubricant on the fork tube and work it down and out of the triple trees. You may have to spead the lower triple tree by driving a chisel into the slot from the bottom side.

Once you have one of the fork tubes out. Remove the plug at the top. There will be a large spring under the plug. Usually it doesn't have much pressure on it with the tube fully extended and if it's the stock spring. With the plug and the spring out, you can pour the oil out of the tube. Notice which direction the spring comes out of the tube. I must go back in with the tapered end down.

Look on the bottom of the tube where the axle goes through. You'll see an allen head or socket head bolt in there. It' should be an 8mm sized bolt but it takes a "piloted" hex key. Now, you can use a standard hex key but it must be in new condition since the bolt head is so shallow. I have found that a hex key socket used with an air wrench is best to get the screw out. With the screw, you can now seperate the upper fork tube from the lower slider.

Remove the retainer ring in the top of the slider and pry out the old seal. Install the new seal in the proper direction. Reassemble the fork assembly. Now, add the proper amount of oil to the tube before you install the upper plug. The forks take 10.2 to 11.2 ounces of oil each. The lower figure is for a "Wet" refill and the higher number is for a "Dry" refill. If you take your fork tube apart and pour out all the oil, use the "dry" figure of 11.2 ounces type "E" or 30 weight fork oil. If the forks are too stiff with this oil, drop back to 20 weight fork oil.

Good Luck
Steve

First of all do not add oil to your front forks with out draining them first. If you over fill your forks with oil you will damage your forks. To change your oil in your forks, first center stand the bike and lift the front wheel by putting a jack under the motor. Remove the front wheel and axle and put a pie tin under the fork tube. Reach up into the bottom of the fork tube with a hex key and loosen the screw but do not remove. Now take the air pressure cross over tube off, this will allow you to unscrew the fork tops( On some bikes you may have to put a towel on the tank and unbolt the handle bars to get them out of the way.). Pull the screws out of the bottom of the forks and gently pull down the oil should come out now. If you need new fork seals take the lower tubes off and replace(You may need to take off the fender and hang the calipers with wires.). Turn the lowers over and dump out the oil and reinstall fork lowers. Snug up screws and sealing washers on the bottom of forks you can not tighten till you put on fork tops. Now pour in measured amount of oil, again do not over fill. Put on fork tops and air crossover tube. Now tighten screws on bottom of fork. Finish reassembling bike.

280 ml on the older models, and 320ml on the newer models.
1. you need to elevate the bike with a jack or something so the front wheel is off the ground.
2. undo the Allen bolt on the side of the fork, then proceed to take the main wheel socket bolt/bar out, so the the wheel comes off, the speedo drive will come off leave that hanging around lol.
3. take of the socket bolts attaching the brake caliper to the fork, dont leave it hanging secure it somewhere, so you dont damage the brake cable tube.
4.take handle bars off, one allen bolt on each one.
5. then unscrew the the 2 socket bolts that hold the folks on, if you follow the folks down you will see 2 socket bolts take them out. do the same on other folk.
6.then pull one folk at a time down, maybe tap it if its hard. and you will have the folk out in your hands.
7.unscrew the big socket bolt at the top of the folk out, but apply pressure, sometimes the bolt will fly off, so be careful.
8. take the big long plastic tube out along with the spring, and tip the folk upside down and pump it to get most of the oil out.
9.then go to the bottom of the folk and undo the allen bolt, when its moving around freely and not coming out put the spring in and push down and twist the allen bolt should come straight out.
10.pump it a few times and then you take the folk tube out completely and give everything a clean, it will be stiff when you get it near the top so get momentum and yank hard and it will pop out.
11. then the bottom pit of the folk that the tube goes into, if you look into it you will see the oil seal, take the cur-clip out and it should come out pretty easily.
12 give the folk tubes a rub down with fine sandpaper say 1000 grain or 800 grain, to get rid of little bumps, look carefully feel it with your hand, to see if theres any pitting, you will be able to see it, thats not good but make sure its not on the part of the tube which goes up and down the oil seal when compressed down.
13.put folk tube back in the bottom of the folk, then put spring in puch down tighten allen bolt.
14.put new oil seal on and push it down its best to use a oil seal hammer tool thingy, but if your careful you can tap it down with a hammer and something small and flat at the bottom, i used a bolt, worked well.
careful dont damage the oil seal.
15. put cur -clip back in, it should click, make sure its on the closest ridge to the oil seal.
16. put 280 ml, of oil or if you have a newer model 320ml, of fork oil in the tube, pump it a few times to get air out and oil to the bottom chamber.
17. put the spring back in and the long plastic tube, and put the top bolt on for now not to lose not to tight.
18. attach the folk to the bike again and same with the other one, make sure you align the little ridge on the top of the folk, with the top of the steering bar, the top steering the bar the folk go into last. its late lol getting confused lol. oh and when y0ou align make sure you tighten the bolts holding the folk in place.
19.then put the steering grips/bars back on and then tighten the top bolt tight cant remember the torque setting. then you know everythign from there. phew

Hi,

I was told by many people it was a hard job.
I didn't think so.

What you need is:
New Seals.
8mm Allen Key.
Half Inch Stocket bar AND Extender.
Extra Fine Sand Paper/Polishing Device.
Fork Oil + Measuring Jug.
Threaded Bar with a Two 19mm Nuts Locked to each other on one end.
Spanners.
Screw Drivers.

How to do:

First Get the Front end off the Ground (ALOT, Center Stand on Bricks for extra height.)

Remove Front Wheel and Brake Calipers.

Open Drain Philips Screw on Base of Fork (Both Sides). Dont Lose Rubber washer under screw. Watch Out Also for Oil Being under Pressure.

Remove Nut from TOP of Fork (Alowing Handles and mirrors to come loose).

From Top you can see down tube has Nut/Cap with a Square Half Inch center. Use Socket Bar (and Extender if needed) without Bit to Remove reach in and remove. Watchout for Spring Pressure under the Cap/Nut.

Use Screw Driver or Hook of some kind to remove Preload Spacers, Washers AND Spring from Fork.

Slide your Threaded Bar with19mm Nuts (Make sure they are Locked Tight together at one end) down into the Fork and let it catch on the Oil Damper at the base. You will know when it's cought because you wont be able to spin the threaded bar anymore. This will stop the Damper from spinning while you undo the Allen Bolt at the very base under the fork (Outside).

Use Allen Key to remove Bolt from Underside of Fork While having someone or somthing hold the Threaded Bar form spinning.

Now look at the Old bust/leaking Oil Seal. There will be a Clip/Locking Spring in a Groove holding it in place.

Remove Clip without Damaging any part of clip or fork.

If Everything above was Done, you can now give the slider( Bottom Part) a big tug and it will all come lose.

One Part of the Oil damper will either fall off, or be left in the slider(Bottom Part). It slides over the Damper in the base of the tube.

Clean Everything.

Clean Again.

Polish Tube.

Clean Again.

Remove Two Split Washers from base of Tube and Copper Washer. Remove Old Oil Seal.

Place New Oil Seal on Gently.

Replace back on Copper washer, followed by two split washers.

Use Grease as a kind of glue to hold the part of damper that fell off back on.

Slide Slider back onto Tube.

Screw Allen Bolt back into base of slider as per originally was (Remeber to hold Threaded Bar if it starts spinning)

Push Gently new Oil Seal into Fork Slider for Snug Fit. Be Gental.

Replace Clip/Spring over top of Oil Seal Locking it in place.

Remove your threaded bar from top of Fork.

Replace Spring into Fork.

Replace Philips Oil Drain Screw into base of fork (Dont forget Rubber washer).

Now: For a GT550 (I am told also KZ550 but can confirm) you need 300ml of 15 weight Fork Oil. EACH Fork. So a Total of 600ml whole Job. IN EACH SIDE YOU WILL ADD ONLY 300ml of FORK OIL. (15w)

After this. Replace any washers, Preload Spacers and so back into for.

Replace Cap/Nut into Fork Tube with Socket Wrench and Extender.

Replace Handles and Moirrors and Nut holding both of these.

Replace back onto bike the Front Wheel

Check Brake Calipers for leaks and Pad Wear. It's Very Cheap to get new Pads. Not cheap to have months off work after a crash.

Replace back onto bike Calipers.

Pushing Bike (Not ride) test Brakes and Suspension.

At This point I am thinking your done. You may need to Add Air Preload into the Fork via the Air Valve. 4PSI is a Starting Point. I have run upto 15psi. Without Air in the Preload you may find it too soft. Upto you.


Did I Forget Anything?

hi,replacing the seal is quite easy,although it will sound complicated,jack up or lift the bike off the ground so that the front wheel is in the air(about 12-14 inches should be enough,remove the front wheel from the bike,remove each fork leg,this is done by undoing the bolts(4 on each leg)the front fork is quite easy to work on just do one at a time,remove the dust cover from the top of the staunchion tube(larger diameter tube),beneath that dust cover you should see a retaining clip that holds the seal in place,remove the retaining clip(and dont lose it),the seal is now ready to remove,the easiest way that i know to do this is to force a screwdriver through the body of the seal,you may need to hit the screwdriver with a hammer as some seal have a tin backing plate,put a hole through the seal on each side of the fork leg taking care not to damage the chrome of the fork leg,then use the screwdriver to lever the seal out of the fork leg,to reinstall the new seal,put a smear of grease or oil around the outside of the new seal,slide the new seal down the fork leg and seat it squarely into the fork tube,very carefully tap the new seal into place being very carefull not to damage the outer surface,i use a small piece of dowell type timber to do this as the wood doesnt damage the seal surface,i use a small ballpeen hammer to tap the wooden dowell,once you have the seal seated down the tube you should be able to see the groove for the retaining clip,reinstall the retaining clip making sure it is seated corectly,replace the dust cover,if you are going to replce the fork oil or top it up do this once the fork leg is back in the bike,repeat the whole procedure for the other fork leg,once you have done the fork seals reinslall the fork legs back into the bike and refit the front wheel,to top up the oil in each leg,simply undo the large cap on the end of the fork leg,you may have to remove the handlebars to do this,be carefull as the cap will be spring loaded and can easily fly off if you are not ready for it,top up or fill with the correct weight oil for your bike(normally a 10w oil),check with your local honda agent for the correct quantity,normally between 400-500 mls,this all sounds quite complicated but is actually quite easy and can be done with a minimal of tools,each fork shold take about 1/2 hr to do...hope this is a help to you

to remove seals you will need to remove each fork leg from the bike,i put the bike on the centre stand and jack under the motor to get the front wheel off the ground,after you remove the fork leg,remove the dust cover(if fitted),remove the circlip holding the old seal,you may have to stab through the old seal with a screwdriver to remove the seal from inside the leg(be carefull not to damage the chrome on the fork leg),clean around the surfaces and install the new seal making sure it goes back in dead square,refit the circlip,then refit the dust cover,replace fork tube back in bike and top up with new oil,most bikes take between 300 to 500cc of oil,but check with your local shop as all bikes are different,and you can adjust the amount of rebound damping by varying the amount of oil you put back in,..sounds complicated but quite an easy job..hope this helps

Angela, do you have a Clymer, Hayne, or service manual for the bike? If not you should get one, there is a lot of valuable information in there even if you don't do all the work yourself.

Replacing the fork seal requires putting the front end in the air, disconnecting everything from the front wheel (brake lines, speedometer cable if there is one), and dropping the wheel and fork tubes CAREFULLY to separate the two pieces of the fork tubes. Then grab the old seal and replace it with the new seal.

This short description is a VERY abbreviated and simplified version. It's not hard once you have done it a couple times but be very careful not to bend anything in your forks. They have springs inside them too. Change the oil while you are in there. Usually 10 or 15 weight fork oil but look in your manual. If you can't find a manual post again with your bike's year and we will see what we can come up with.

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.