An Unholy Union II: Wp Extreme 50mm Conventionals on a G/S

Not that I could tell. What's weird is that I don't loosen the bottom triple in my retorquing process and each time I take up the slack with the top bolt, the fork legs stick about 1/16" over the top triple where they were previously flush. So either I didn't set the bearing races anywhere close to seated when I drove them in, or the fork legs are slowing migrating up through the bottom triple despite being clamped - 15 ft lbs on all the pinch bolts - AND the top bolt is slowing unthreading itself, AND the top triple is sliding on the stem despite being clamped. Same thing three times now, roughly a skinny 16th each time, so it's pretty much impossible that the races were still just under 1/4" from being seated. So however unlikely/unbelievable the alternative is, it has to be the case. :huh

They came from BMW. This time they were a swiss brand I'd never heard of rather than the SKF or FAG bearings BMW has sold in the past. I've had good luck with the NTN bearings cycleworks sells for a fraction of the price BMW wants.

Not pulling the stem out of the bottom triple is it?

J

Hey guys, I finished modeling the rdubbs triple clamps in solidworks so if anybody else needs the files i can email them to you in iges or solidworks formats. I will hopefully have my bike back on the road in 2 weeks.

Hey AW,
despite heavy efforts I failed to seat my lower bearing at the start... I also failed to use the stock bearing cover under the bearing. A bit of riding kept beating the lower bearing down, I kept re-torquing at the top till I rand out of adjustment (the blind nut was bottoming on the stem). Then from a bit more riding like this the upper bearing knocked bit of damage into the stem that had to get wet and dryed out in order for me to get everything back in place with the correct bearing covers on top and bottom.
Obviously these things aren't idiot proof. Also, there is very little room till 'play'.
I'd be getting a sharpie or something and marking all the fasteners and other components to see what is moving/loosening.
iPhone typing is annoying... Internet not on at our new place yet. Good luck.

yeah, after a few riding/tightening cycles the play seems to be gone for good. I'm guessing the stem may not have been fully seated in the bottom triple or the bottom bearing race wasn't totally seated. I still haven't been able to work the stiction out of the system and took the bike to a suspension guy. He's saying he doesn't think it's the internals and comes down to an alignment issue of some kind. Either the axle, wheel spacers, or the triples (!).

Silly question.. and It may have been answered before, but how much fork oil or what level did you guys use on your shortened WP 50mms? Im rebuilding these set of these that I lowered by 10cm for my XT500 and could do with any advice on this, thanks!

If I recall correctly I think it was common to run around 125-130mm air gap for stock forks/bikes.
With springs out and fork fully compressed the shortening of the fork with the lower spacer will only change the volume by a small amount, but it should still be air gap we are measuring rather than volume.
If you can be bothered laboriously searching through the difficult forum KTMtalk has a fair few old threads talking about working and tuning these forks.

I have wondered aloud in this thread somewhere before about how the air gap/oil volume should change when we shorten them. I am not sure if we came up with a proper answer.
To me, when shortening a fork, it would make sense to to also proportionately shorten the air gap, so
180mm travel: fork shortened 10mm..... do the math... reduce air gap by around 6-7mm...
but then air gap is a tunable thing anyway.


I hope that helps a little.
Please post some photos of your fork swap and explain a bit more of what you have done and are doing,

Thanks man!

I also agree that KTM talk is a great resource, but one where you need to set aside a lot of time to sift through and find what you need. :/

My notes say that I originally filled these with 800ml (not sure why as the manual says 750) of quality Shell ATF, but they did feel quite soft on the bike when moving it around the garage, tho I have to say I didnt fiddle with the adjusters at all, I should have really before I stripped em again. hmm....

So I was thinking about this when I asked on here (the only place I reckon where anyone has any experience of these forks nowadays as everyone KTM has moved to USDs sadly and lost the info on these). So, I reckon now that I would need less oil than more, as there is less overall volume in the leg chamber now with the leg shortened. So with that in mind, and the fact I have a proper fork oil tool now I will do the refil by airgap instead and try them on the OEM air gap and see if they come out too hard or soft as I can always add/remove some oil later I guess.

So, anyone know what the airgap is meant to be? My manual just says 750ml I think?



Oh and yes, background and what I am up to....

I had these forks on a brand new '99 KTM250EXC and always found them 'hard', even when on soft settings, when on trails at slow speed. When the going got faster and the riding became more spirited they came into their own. Of course that bike was a lightweight machine that was stiffly sprung.

At the same time I had the same forks on a '98 620 SC that I motarded, it was one of the first in my area back in 1999/2000 or so. That bike handled really nicely on the road but felt a bit 'long', due to the rake/trail I suspect, but the forks handled the road bumps really well and what made me want to use them all these years later on my XT500.

The thread for the XT is here, if you wanted to see my progress, or lack thereof:
http://advrider.com/forums/showthread.php?t=877636

Found some info about the air gap, here:
http://www.dirtrider.net/forums3/showthread.php?threadid=18716

Essentially its 140-160mm, but some have said you can go to 120mm. With the shorter forks Im thinking it will be 120... I will report back when Ive done some measuring the garage....

And also here where they say 155-160mm:
http://forums.mxtrax.co.uk/showthread.php/280786-how-much-oil-goes-in-wp-50mm-forks-on-a-98ktm380

Ok, I decided I would go with 135mm and see what I think when its on the road. Its pretty easy to mess with these forks so Im not worried about rework, lucky as I had a few bits of fun while doing this, oil over the worksurfaces is all part of the experience er...

Interestingly I did use 750ml last time as I had 500ml left in my container (I had written that on the side), so no idea why my notes said 800, but Im now thinking someone suggested that and I wrote it down.

At 750ml the level was 160mm FWIW... so 800 is probably 140 or so.

I think Im talking to myself, but Ive rolled the bike round the garage and the forks feel good, less diving than before under braking. I still need to ride the bike, but right now Im ok with my oil level.

damn... go ride it and let us know:)

Roads here are covered with salt so I have an excuse! Ride it an let us know how it feels... I will be doing a 4860 conversion so I will need lots of encouragement as the project is executed...

go man go! oh... and pictures are always a good thing!

Haha! Sadly my fuel tank is still at the painters awaiting the dents taking out or I would be out on it and not replying to the thread LOL!

sweet!

Does anyone know where I might be able to get spare parts for these things?
It appears that both rebound springs broke in my forks and on one side the little bits have chewed their way through the rod taps and all its tiny parts.
KTM spare parts places only list the entire cartridge and then it isn't available anyway...

Maybe a set of gold valves? Anyone used them in these forks?

I think the best bet would be to just buy a spare set of forks. I watch oz ebay (searching for used ktm forks) for them and aside from the current batch of overpriced motorbike wrecker wp50 forks and parts that are on there now ever now and again you can buy sets of WP50's for 100-250 or so which I think is a good buy.
I got a spare set off ebay for $150, and I have actually gone through them and used a fair few parts within my first set of forks as the spare set was in slightly better condition internally.
I almost bought another set for $150 a few months ago but decided against it.
I hate to say it, but little bits of spring metal going all through the forks you might be better off starting with another set of forks and using these ones as the spares

another thing if you are in a rush, outside of ebay you could contact some of those wreckers that list WP50 forks for stupid prices. They never ever seem to sell them at those prices and just constantly relist- thus I would think some of them might be willing to take a more reasonable price if you contact them directly.

You might be right I think...surely if I buy a second set I'll be able to make up one good set.
The rest of the forks seem ok, the compression side rebound spring only broke as I was pulling the spring off the rod (with my hands...so it had about 8 seconds life left). The rebound side had been banging up and down in there for a while and destroyed the shims, rod tap etc.

Not in a particular hurry...got a bit to do. Engine bits, gearbox casing, hubs and FD parts are all off at the hydroblasters. Frame etc is off getting painted.

I was just trying to get something finished on it...just one component.

Did you find a source for the fork rebuild kits? Seals, bushes, o-rings etc?

Yeah, I suspect you got a bit unlucky with yours. As rough and used as both mine looked on the outside, they were quite OK on the inside.

For rebuild stuff,
part number R906 for the oil seals and dust wipers (and a few other little associated bits)
part number R904 is the 'full' rebuild kit, it has the above with some other bushings and a few other bits,
check the price on the R904 kit and you will see why buying a spare set of forks, which hopefully is good inside, is probably a good idea!

If you are ever in a pinch and need to borrow bits from my spare forks before you find your own spare set just shoot me a PM. I'm heading up north for a month and my G/S project is currently in deep sleep.

Manual on Ebay right now.

I wonder if it is the same one you can download for free?