Front Fork Oil Change and heavier weight oil

[Vroom4]

I was wondering if it would be possible to just swap out the fork oil without disassembling and rebuilding the whole fork....?

I'm almost 100% certain they have already been rebuilt, bc the seals look perfect and it does not leak at all. I've checked multiple times.

My main problem is that it feels like the preload on the forks is set really low, or maybe the rebound is completely out... idk. The bike dives pretty bad on the breaks and once down there, it doesnt want to come back. Almost like the forks are sagging.

I was thinking that putting some fresh oil in there may be a good first step to try. Also, would putting a heavier oil help? I know my brother put heavier oil in his KLR forks a while back and it was a much better ride.

What does everyone think? I'd rather avoid a full rebuild for now.

These two links were a big help
http://www.fmbikes.com/2012/02/fork-seal-job-for-the-xs400/
http://www.fmbikes.com/2012/02/fork-seal-job-for-the-xs400-reassembly/

 

[Vroom4]

Also, maybe dropping in progressive springs would help? Anyone know where to get some for the 33mm xs400 forks?

 

[Drewcifer]

I owe you guys a thorough write up on my fork seals/fork oil change.

Once I replaced my fork seals with new ones and put in ATF instead of fork oil I had a very heavy, steady front end They should NOT dive at all. if they are diving, you may not have enough oil in there to see how leaky they are.

So the awful advice I must give is this.

Man up, buy the 9 dollar set of seals, and get er done. You'll be more manly for it.

now to post that write up....goddamned cable to the card reader ...where did I put it.....gruguguuwoeroerouwewrebadffrabababbddrlkslksdlfj!!!!

 

[drewpy]

I used the "Minton mods" on oil, springs and levels.


Basically I out in 20w fork oil (engine oil froths and is crap then) progressive springs and 6" level from the top of the fork fully extended.

http://www.650central.com/tech/mintonmods.htm

 

[Lou Ranger]

I was wondering if it would be possible to just swap out the fork oil without disassembling and rebuilding the whole fork....? ... What does everyone think? I'd rather avoid a full rebuild for now.

It is possible, I have done it.
But you will not gain acceptance from the purists among us

But what can it hurt? Having the right amount of new oil (versus whatever amount and quality is in there now) can only be a good thing even it simply points out that there are other problems in there which have to be addressed.

Here's how I did it: Drain the forks, siphon all the gas, remove the battery, hang the bike upside down by the front wheel and inject the right amount of fork oil into the drain holes with a free oral syringe from a drugstore.
Caution: don't just reverse the process without first installing the fork drain screws, or you'll be

The whole story starts here from post #25 on: http://www.xs400.com/forum/showthread.php?t=8139

 

[bcware]

Changing the fork oil without rebuilding the entire fork/seals is considered normal maintenance.

Why would anyone think this is strange and or not possible?

 

[Vroom4]

I'll probly just pour in some 20w then and see how she does. I like the idea of injecting it into the drain hole, but i would think this would be harder to get the exact measurement down. Pouring it in from the top(removing the spring clamp and plate) seems easy enough too...

Does anyone know the exact amount of oil that should be placed in each fork?

 

[bcware]

I think that was a joke.

You can fill it from the top. You'll want to raise the front wheel off the ground and remove it. The reason the wheel needs to come off is so that you can "pump" the excess fluid out of the fork by compressing it.

If you do this you're 95% of the way there to removing the forks, however.

Before you do anything download a manual on here. It covers everything.

 

[Vroom4]

Yea i figured the hanging upside down was a joke... I'll def be removing the forks, done it before so no worries there. I'm just hesitant to do a complete teardown and rebuild on them.

Will probly just drain them and fill up with fresh oil from the top. Just need to know how much fluid to put in each fork...

Also, anyone have a good link for progressive springs??? I've also heard of modern valve emulators for older forks, but have yet to hear of anyone try them.

 

[Lou Ranger]

Yea i figured the hanging upside down was a joke...

Not a joke. Though the telling of the tale does kind of illustrate how we can sometimes take ourselves too seriously.
That's how I did it on the sr250 - because all the workings in the top of the fork tubes were fused in there and would not budge, would not come out and would not allow a drop of oil to penetrate down past them.
Obviously, if everything comes out properly you don't have to invent an new procedure - just pour it in the top.

But I knew there wasn't enough oil in there so after removing the drain plugs and pumping out all the black watery oil, rather than pack up and take it to a shop, I simply elevated the drain holes one by one and measured the precise amount of oil stipulated using the oral syringe. As I recall it held 12 ml., so I simply put 14 syringes full in each fork (= 168 ml., per spec). I used HD fork oil.
Was it as good as a total re-build?
Likely not, but it was quick, easy and the fresh thick oil made a huge difference in how the bike handled - no kidding.

Different models have different fork capacities - 2 different amounts for sohc depending on your model:

View attachment 9587
​

The dohc (Maxim & Seca) is way different - manual says 263 cm3 in each tube.

 

[bcware]

I was picturing you trying to pump the forks up with oil through the drain while they were still upright and on the bike

 

[Lou Ranger]

I was picturing you trying to pump the forks up with oil through the drain while they were still upright and on the bike

I wish now I had taken a picture - but it was before I got the xs400 and joined a Forum.
Visualizing what such a picture would look like, I now recall that I took the mirrors and rear turn lights off and loosened the handlebars so they would not poke into the ground. I put a couple of other-season car tires on a slope in the lawn, laid the bike on it's side on top of the tires with the drain plug slightly elevated above the top of the fork and filling was quite easy. Flipping it around to do the 2nd fork was actually the hardest part.

Believe me, I would much preferred to have had all the paraphernalia come out of the tops of the forks properly but, like I said, having a full compliment of new oil in each fork make it all worthwhile. Sometimes the ends justify the means.

 

[Vroom4]

Thanks guys! I'm hoping I have some time to do it this weekend. I may also take a stab at shaving down the oem seat!

 

[john slaughter]

Hello- I'm new, just acquired an '82 xs400, and the forks seem to need oil, I understand the orthodox method of removing the hardware on top (circlip and spring cap) but fear of flying circlips and springs prompts the ?? what about injecting oil into the drain hole? The structure above is not airtight, or else you couldn't add oil from top anyway, so no bleeding would be required. What do you all think?