How to rebuild the forks and seals on a 1978 Yamaha XS400

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[@TheArmouredFist]

Workin on a 76 XS500, and this video helped immensely. Tip for everyone, We rounded out our allen drain bolts, so we drilled them out with a drillbit!

[@marcdouglas6466]

I was going to pay to have mine rebuilt, but this honestly looks like a good time and you completely demystified the process. Thanks for an awesome video.

[@chugg535]

Thank you RiderForge for the video, very well done, and informative.

[@nurseratchet8535]

Thanks for the video, first one that I found that told me clearly how to safely defeat the circlip at the top of the tube without resorting to profanity.

[@alxd21]

Very nice and informative video! Thanks a lot!

[@78JGK]

Thanks for that. Don't suppose you can remember what the stiffer springs were from? Got an on going build that will one day be finished.

[@aaronbrown8927]

Great video - what lubricants did you use for the bearings, and the rubber seals?

[@derekgreen7041]

dude thank you so much for posting this. im currently rebuilding my 82 xs400 heritage special. and im at the forks! this helps a lot. what kit would you reccomend I buy to replace seals and rings and such. just need to know which one to buy.

[@RiderForge]

+Derek Green Rings as in piston rings? What kind of seals? Fork seals or other engine seals? Thanks for watching by the way.

[@78JGK]

If you're running a jacked up rear end do you have heavier fork springs to compensate the extra weight thrown towards the front? Cheers.

[@RiderForge]

+78JGK I did use heavier spring up front, yes. I was using 14" eye-to-eye rear shocks. The bike handled very well. No complaints from me. Shifting the weight to the front effectively increases the pre-load on the spring. This will firm up the ride, but with stock spring you may lose a lot of travel. The firmer springs help compensate for any lost travel. I'm no suspension expert, but on the street I was dragging knee all over the place with this bike and having fun; it did what I wanted it to do.

[@90blacknight]

Hello. I did not do a full rebuild of my forks, as they weren't leaking, but I changed out the fork oil on my 81 xs400, and used 20w synthetic fork oil, 142cc's in each fork. I still find the suspension very soft. The springs took quite a bit of force to compress by hand, so I'm thinking the springs are ok? How do I know? Is the stock suspension setup just too soft to begin with?

[@skippygirl959]

90blacknight did you ever find a solution?

[@burninghate88]

was wondering how to get that top cap/screw off to add the fork oil. If I remove the black cover I see a dome shaped hole...how do you unscrew that?

[@RiderForge]

+burninghate88 Good question. It doesn't unscrew. Use a large Phillips head driver or something similar and sturdy to push down hard on the dimple; this will expose a circlip. You need to pry the circlip out. Once the circlip is removed the dome-shaped metal piece will come out; it is under a fair amount of spring pressure. Just maintain the force you needed to apply to expose the circlip and SLOWLY release. All will be good. The worst that can happen is the circlip can go flying off when you pry it out. Only do one fork at a time unless you have a lift for the front end or plan to remove the forks. In fact, I would recommend lifting the front end off the ground regardless. This is easily done if you have a center stand on your bike.

[@burninghate88]

Awesome, I've been scratching my head trying to figure this set up out. Thank you very much!

[@nickkluger97]

+chiangxiong How do I fix it if the bolt that holds everything together at the bottom of the fork is not tightening and instead spinning the inside of the fork?

[@RiderForge]

+Nick Kluger Assuming nothing is stripped or otherwise broken it is likely that the bolt is simply not catching the threads on the inside. The bolt screws into an inner tube/rod. This tube/rod can be hard to position when no pressure is put on the springs because it will move up and down and side to side. You have to drop this tube/rod in, hold the entire fork in a vertical position, and thread the screw in; this usually takes me several tries to get it all lined up. Alternatively you could try and use something to push on the springs/rod/tube once it is inserted into the fork to prevent it from moving or spinning, but this is very hard to do by yourself with only two hands. I generally just keep dropping it in and if the bolt won't thread I pull it out again and try until it catches.

[@nickkluger97]

I got it, the issue was that the damper rod was just spinning, I shoved a broom stick in the hole and that stopped it. It's all good now.

[@banopanov3281]

yamaha yzf r125 are about the same to disasembe the forks that is

[@derekgreen7041]

most likely that lol still figuring out what stuff called on these. would you mind posting a link to the ones you got on here? cause I have no idea where to start looking lol and ill just buy the same set you got.

[@RiderForge]

+Derek Green I just bought mine on ebay. Search for "xs400 fork seals" and they will show up; lots of common parts are on there for relatively cheap. Just make sure you're getting them for the correct year.

[@derekgreen7041]

because ive been looking but im not sure what size differences are with different forks and different size seals.

[@derekgreen7041]

+chiangxiong alright ill do that :) thank you!

[@RiderForge]

+Derek Green Yeah as long as you buy for the right year you'll be fine. Make sure you know what engine type you have too. DOHC versus SOHC; this will determine what you need.

[@derekgreen7041]

Mines dohc lol figured that out with a friend a couple days ago.

[@derekgreen7041]

lol sorry. fork internals. like the pinch rings and seals for the inside. I already found the kit for the engine and ordered it seal and gasket wise.

[@RiderForge]

+Derek Green I'm still not sure what a pinch ring is; you're probably just calling it something I am not used to. For seals I used All Balls and they worked great; anything that is brand name should be fine though; it's worth spending the extra dollar for better quality.

[@shnrmrz68]

Age 6?

[@78JGK]

Thanks for that. Don't suppose you can remember what the stiffer springs were from? Got an on going build that will one day be finished.