I Want to replace front fork seals on my 2004 Yam XT660X and need to know Fluid and Quantity used. Are there any manuals available for this model. I have replaced seals on some of my previous bikes.

Well, yes. The fork seals are located at the top of the fork slider un the "slide tube cap". This makes me wonder exactly what did you replace when you say that you just replaced the "fork seals". To get to these oil seals, you have to disassemble the forks tubes. Remove the front wheel and fenders. Down where you took the axle out, look up into the end of the slider and you'll see a socket head bolt, 6mm. Loosen this bolt before you take the tube out of the triple tree. Remove and repair one tube at the time. When you get the slider off the top tube, you will see a retainer ring in the top of the slider. The seal is under this ring. The new oil seals must be replace squarely in the tube. When you reassemble the tube and put it back in the triple tree, there is a specific amount of fork oil that must be added to each tube to properly refill it. You must use the "dry" quantity when refilling the fork tube because you disassembled and completely drained the tube. I'm sorry but I don't have this quantity of fork oil for this late of a model bike. I work on the earlier model bikes only.

good luck
steve

Yes your fluid may need to be changed if you want a more firm front end. I don't know what type of fluid you have in the forks now but what you need to do is to go with a thicker oil. In my '94 FXDWG, I went to PJ1 30 weight oil. Since I don't have a book on your late model bike, I can't tell you how much oil to put into each tube. There is a "wet" and a "dry" quantity to add when you've drained them. If you simply drain the oil and refill the fork tubes, use the "wet" quantity of oil. If you disassemble and clean the tubes out, use the "dry" quantity when you refill.

To drain the oil, look on the trailing side of the fork sliders. You'll see a screw or a set screw in the slider. Take this plug out and some of the oil will simply flow out. To get all of it out, hold the front brake and push down on the handlebars. Now, oil will spray everywhere so don't do this job in your living room. Once you get the oil out of both tubes, reinstall the plugs and refill the tubes one at the time by removing the top cap out of the tube and pouring the prescribed amount of oil into each fork tube. Ride the bike and see if the front suspension is too soft, too firm, or just right. Remember, the heavier the viscosity of the oil, the more firm the front suspension is. If you can't get it right, you might want to consider changing the springs in the fork tubes.

Good Luck
Steve

There is a seal in the "slider" of the front fork, the part that moves up and down. I haven't had a chance to work on the later forks but the earlier 41mm forks are quite simple.

Start by taking the drain plug out of the bottom of the slider and work the slider up and down to blow out all the oil. Then, remove the front wheel. Remove the top cap from the upper tube and loosen the top plug. Now, with the top plug loose, loosen the pinch bolts and slide the fork out of the triple trees. Remove the top plug carefully, There is a BIG spring in there. Once you have the plug out lift the spring out and set it asside. Notice the tapered end of the spring. It goes back in first. Turn fork tube upside down and allow as much oil to drain out as possible.

Now, look at the bottom of the slider where the axle goes. Up in a hole there is an allen head bolt. it is designed to use a special wrench but a regular 8mm allen key in GOOD shape will take the bolt out. It's best to use an air wrench to do this with. With the bolt out, the slider should slide right off.

Down inside the top part of the slider is where the seal is. Theres a snap ring, a spacer, and a seal. Replace the seal and put a little oil on it to assist reassembly. Put everything thing back together and add the appropiate about of oil. Since your forks are much larger than mine, I have no specs as to the quantity. The owners manual should tell you or a call to a local Harley dealer. Sorry but thats a good as I can do. There is a "wet" measurement and a "dry" measurement. Since you disassembled your fork, use the "dry" quantity of oil

The best way to do this is to get a clean containe and carefully drain the fork oil into it and measure how much came out nad replace the same amount.
I use a measuring cup from an automotive paint store.
Your old seals should be good but give them a good visual check first.

dissassemble forks and replace fork seals.(and oil) becareful forks are under a lot of spring pressue. use a workbench vise to hold fork tubes. you will need the manual for this. plus you will need to know the "proper" amount of fluid to put back into the forks.

I have a 1982 CB750C the manual says the quantity is the same for all bike before 1982 it says 6 ounces for the air assist fork models. this is from a clymer manual i recently bought. Highly recommend getting one

change the oil seals and oil in the fork,and avoid wheelies on the bike and off road biking 

You need at least .5 liter of oil on each fork.