How do I replace front forks.

[thlillyr]

So I've got so really bent forks and I've got some shiny new used forks to replace them with. So what im wondering is how should I do this. The replacement forks are still assembled with the shocks. Should I leave them on and just bolt the used ones on as is? How can I tell if the used shocks are still good before I go through the trouble of installing them. What kind of oil do I need to fill the shocks. Any other things to look for?

 

[volcomskater77]

read the manual thats available on the site. take off the front wheel, unbolt the old forks from the trees. should be 4 bolts. slide that bent up crap out. slide new straight stuff in. re assemble good as new. read the manual before you try it tho. it gives detailed instructions as to how much oil to put in the forks. 10w-30 is acceptable i believe.

 

[bcware]

My local motorcycle shops all sell fork oil if you want to use that. I'd change the seals while they are off; it's easy and the seals are cheap. If they aren't cheap look around more! They should be like $7 give or take. My advice would be to buy a seal puller as well, but you don't need one. Prying out the old seals is a pain and using a huge flat bladed screw driver can easily scratch the inner walls of the tube.

 

[drewpy]

i use tyre irons to perswade the seals out. I've used those super seals amd have them in for 6 years now no problem.

 

[thlillyr]

So got my forks off. Pulled out the tubes and put the tubes I ordered in and guess what they are the wrong tubes. They are slightly smaller than my tubes. Now I'm stuck with 4 sets of tubes I can't use. Anybody want some xs400 tubes? They apparently don't fit xs400j bikes though.

Any suggestion where I might find the right ones?

 

[WulfgartheBlack]

So I've got so really bent forks and I've got some shiny new used forks to replace them with. So what im wondering is how should I do this. The replacement forks are still assembled with the shocks. Should I leave them on and just bolt the used ones on as is? How can I tell if the used shocks are still good before I go through the trouble of installing them. What kind of oil do I need to fill the shocks. Any other things to look for?

You don't say what model or year [that'll be on the maker's plate on the frame] but bent? Sounds like anything would be an improvement!
Guessing that the inner steel tube is the bent part as the cast aluminum outer tubes would crack and break rather than bend. Your major hurdle is the lugs cast onto those outer tubes. The lugs for disc-braked cast wheels don't interchange with the ones intended for the wire-spoked and drum-braked wheels - and neither do the speedo hubs and cables. While you've got it all apart, you might as well save time and work and put in new oil and seals. When I did mine, the seals had leaked and there was a watery sludge in the bottom. Good thing to get rid of and you can't know till you open it up. BTW the inner spring has a top and bottom.
As a sidelight, the oil smelled of fish! I'm told the Japanese used to use fish oil [they've got more than they can eat] where we use petroleum - maybe still do.
I'm not sure about the length of the systems but if they vary from year to year that could alter the steering geometry - rake, trail, Etc. - and that changes the way it drives [ever try a chopper?]. Bone is harder to replace than bike parts so get used to the way the new system handles lest you get bent into a new shape!

 

[XSLeo]

If the upper tubes are bent, you might want to remove the trees and check them for straightness.
Take the lower tree and place it on a flat surface, like a table top. Use a c-clamp and clamp the trre to the table where the fork tube coms through it. look at the eother side where the fork goes. Is it flat on the table? Move the clamp to the other side. Does the first side set flat on the table?
If not then you need the trees too.
Try taking your original forks apart. Take the tubes to a good bike shop, one that deals with dirt bikes. They can straighten them for you if not bent too bad.
Once you get the fork right, you need to check the frame for straightness to. Get the forks and wheel back on. Get the rar wheel straight in the swingarm. Measure from center of axle to center of swingarm pivot bolt. Get them the same both sides.Now with two straight edges long enough to reach from the behind the rear tire to in front of the front whell. set the straight edges against the rear tire so it touches it front and rear.
The straight edges should be equal distances away from the front and rear of the front tire and be the same front to back.
Leo

 

[OliverB]

IIRC, I believe O.E. spec fork oil is 20W.

 

[thlillyr]

Thanks guys I ended up getting some maxim 550 forks to put on my 82 xs400rj. they fit like a charm. Only difference is I need to move to the 12 inch brake roter and my front end sits a little bit lower.

 

[junior77]

hello im new & i have a -77- im looking for new fork tubes.does anyone know where i can get pair, and how much

 

[xschris]

You should post an ad in the classified section of the forum for a wanted item. Also It would be good to start a intro thread to tell members about yourself Oh and welcome

 

[Arclight88]

Check out this website for a 2-part XS400 fork seal removal/replacement tutorial. Step by step and good quality info!

http://www.fmbikes.com/2012/02/fork-seal-job-for-the-xs400/

 

[thlillyr]

Thanks for the help guys got them on and they work great. They were forks from an xj550 the bolted on fine with one exception the you have to use the larger rotor for the brake as the calipar is higher on the forks. Also the ride is much softer and pleasent then it ever was with my old stock forks.