R1 fork rebuild...

Greg · Post by **Greg** » Mon Jun 11, 2007 12:23 pm

Ok - you know the forks and front end are done, I've done a few hundred miles on them now and all I can say is that the handling is 100% better but that the ride is shite! I can only conclude that the forks either aren't set up properly, or have too much oil in them cos they feel waaaay too stiff. There's also a definite 'clunk' over bumps which sounds/feels like the forks are either topping out, or the races aren't tight. I'm going to check the races this afternoon as thinking about it, I'm wondering if I put enough torque on the lock-nuts... I remember when I re-assembled the stem assembly that the rubber washer between them kept squeezing out. Perhaps it needs to go and the lock-nuts be torqued down harder..!

Presently I have 7.5wt oil in them, I have 5wt to replace it with which is the standard R1 weight. I've no idea what the spring rate is (can anyone tell me how to find out..?) but have the pre-load screwed right out. Other settings are in the middle of the ranges.

At the moment, the max no-load travel is 140mm (from the bottom of the seal to the top of the casting on the bottom of the fork leg). With the bike's weight (static sag?) it drops 45mm to 95mm from the casting. With me sat on it (95 kilo

) it doesn't move appreciably more than that...! With me bouncing it up and down as hard as I can there's still 40mm left to the bottom of the fork. Now I know it won't get right down there, but I would expect more than 55mm of dynamic travel! For the initial part of the static travel the forks move nice and freely, but after that there's a fair bit of sticktion.

I can't see any obvious kink or creasing in the fork tube, or any inappropriate wear on the plating so I'm not convinced a leg is bent, but I think I'm resigned to having to strip them down to check and also make sure they're completely empty before re-filling them.

So, has anyone done a full strip?? Conventional forks are a piece of pudding, but I've never tackled a set of USDs before... any hints, help or manuals??

Cheers

Greg

youngy · Post by **youngy** » Mon Jun 11, 2007 2:17 pm

USD forks are not vastly different to strip to RWU cartridge forks.

Have you got the forks parallell? Loosen the spindle pinch bolts, sit on the bike and bounce it up and down, then retighten the pinch bolts. This floats the legs to the correct position on the spindle and makes them parallel, otherwise this could cause the stiction that you mention.

Otherwise is it possible that they have the wrong springs in there? Too long? i.e. Ohlins springs are often longer than stock and require a shorter or no spacer.

Is it possible that they were took apart and rebuilt with the top caps set up wrongly? This will put the rebound adjustment way out and "could" give you a hydraulic lock in the cartridge, causing limited travel.

You could take the fork legs off and compress them buy hand. Compare how they behave to each other. This could show if one of set up differently to the other internally.

Running a Teflon based fork oil such as Ohlins on the road can lead to clogged valves and shim stacks. It doesn't get hot enough to thin properly and turns to a gel in the valves, stopping hydraulic flow. So don't use Ohlins oil on the road.

There's a pic here shows the assembly http://www.ronayers.com/fiche/501_1848/ ... rent=31910

Greg · Post by **Greg** » Mon Jun 11, 2007 3:45 pm

Thanks for that Martin - I'll have a look!

G

Greg · Post by **Greg** » Mon Jun 11, 2007 7:29 pm

Martin, I think the alignment is ok - the legs were loose mounted a few times and tightened from the top down, but I suspect that they'll be coming out this week so will do the bounce thing on re-assembly. When I first got them they stroked fine, no undue resistance or sticky points but as far as spring length and cap assembly is concerned I won't know til they're apart. That said, and looking at the following link

R1 fork strip

makes me think that I've overfilled the legs as there is residual fluid in the cartridge that should be separately expelled when draining - all I did with mine was invert them and pump a few times. The link is a very clear 'real world' pictorial description that I think will be useful for anyone having to do this..!

Anyway, the weather's due to be a bit shite later this week so I'll have a go then!

TTFN

G

youngy · Post by **youngy** » Mon Jun 11, 2007 8:16 pm

Greg you have to do lots of pumping to empty them. The cartridges are so much more convuluted than a damper rod fork it takes much more effort to drain them.

Make sure you set the forks caps with the right gap when you reassemble.

If you're unsure what I mean let me know and I'll try to explain.

Post by **Max** » Tue Jun 12, 2007 12:33 am

martin young wrote:Greg you have to do lots of pumping to empty them.

You sound like one of those spammers trying to sell me a "wonder drug"...

Post by **Kevtrx849** » Tue Jun 12, 2007 4:54 am

G'day Greg, traxxion sell a really good kit for working on the R1 usd forks. Nice and cheap but quality stuff. Just type in Traxxion on ebay to find the shop. I fitted racetech 09kg springs in mine with 58mm spacers and 74mm air gap (482 mls of Motul 10w in each leg). Set up seems to be near perfect on the track. Locknuts may be too tight if the rubber washer has squished out, didn't have that prob with mine. Good luck.
CYA, Kev.

Quan-Time · Post by **Quan-Time** » Tue Jun 12, 2007 10:23 am

depending on your year.. mine are blue top 2000's or somethin.. I stripped them (which was a bitch) and got em polished.. got new seals.. took a look at it.. went to the local auth yammy dealer and parted with some cash..

I told him how heavy i was, and told him it was for a TRX not R1.. he said it wouldnt matter.. They pre-loaded them and set them up all for me.. bolted them in and they were so sweet..

Dont get me wrong. im very handy with this sort of thing.. but if you can afford it, just handball them off.. i needed 2 custom tools to even pull them appart. and you need ANOTHER one to put em together.. saying that mine were spring / oil.. Ive rebuilt many "skinny side up" forks like the TRX (dirt bikes, etc) for ppl.. but usd.. dont have the proper tools.. and i couldnt justify the money..

And a GREAT place to get schematics is the world patent office.. I kid you not.. couldnt figgure out the internal screw mech to pull the inner from the outer, the piston rod thing.. found out the model number, went to the world patent web site, found teh full schematics.. made it mucho easier

gotta love copy-right laws.. have to say WHAT they want copy-righted..

Greg · Post by **Greg** » Tue Jun 12, 2007 3:34 pm

Ok - great info there chaps !

Here's what I found ....

As I suspected, the clunking was loose stem bearings

, I still can't work out how they can be tightened enough to be able to lock them without squeezing the rubber washer out AND fitting the tab-washer as well! For the moment I've junked the rubber washer, and plain old torque-locked the stem nuts together.... well, it was ok for my old YR5 !

While the bike was on the jacks I popped the forktops and checked the oil level - sure enough, there was more oil in the LH leg. I drained about 50cc just to see what difference it would make and yes, it's a lot more pliant now but without doubt I now have different volumes in each leg, which from what Martin suggests will mean a complete strip just to evacuate all the oil from the cartridges. I'm going to have to get hold of an R1 manual from somewhere cos I'm not sure if there should be different volumes...

Quant - I'm a sucker for punishment and will try anything once (besides, the guys who did my forks last time f@cked it up!) and have seen that the 'special' tools might not be so hard to fabricate. Did you get a chance to look at the link I posted above? It'd be interesting to hear if it's a reasonably accurate depiction of how it is ..!

Cheers

Greg

youngy · Post by **youngy** » Tue Jun 12, 2007 4:16 pm

Greg you don't need to strip any more than the top caps and springs. Then invert and pump, pump, pump!

When you've got all the oil out compress the legs and fill to the correct level, pumping away to expel all the air. You'll notice a difference in squelching when the air is all out.

Refit the springs and spacers. Wind the nut down as far as you can by hand. Ensure the preload adjuster is recessed 25mm in the top cap. This is important. Screw the top cap on til it bottoms on the preload adjuster then back the nut up to lock the top cap in place. Screw the top cap into the leg. You're done.

Note: Before you start to take the thing apart wind the rebound and compression all the way off.

Greg · Post by **Greg** » Thu Jul 05, 2007 9:10 pm

Hey Martin ..

It sounds like you've done this before...

I've popped the top caps and drained/refilled with 5wt oil - cheated slightly cos I left the legs in the yokes - but this time I've got the right volume in each leg (I was about 80ml over in the left leg..!) But since re-assembling everything, I've only got 5 clicks on one of the top nut damper adjusters...

You mentioned that the preload adjuster needs to be recessed 25mm - do you mean that I have to wind it in (apply preload) before refitting the cap to the damper rod..??

Cheers

Greg

youngy · Post by **youngy** » Thu Jul 05, 2007 9:49 pm

Take the cap off the damper rod. Can't do this with it on.

Wind the preload adjuster in or out until you have that 25mm recess inside the cap.

Wind the cap back onto the damper rod until it bottoms. Don't wind it on using the preload adjuster!

Then back the cinch nut up to lock it tight.

Do the same on the other fork leg. Then the legs are both "zeroed" correctly.

Any clearer?

Greg · Post by **Greg** » Thu Jul 05, 2007 10:45 pm

Yeah - I think I see where I went wrong now...

Just have to see how far I can boing the springs across the garage this time

Cheers

G

youngy · Post by **youngy** » Thu Jul 05, 2007 10:56 pm

If you wind the nut down it should hold the springs in place while you take the cap off and set it.

Have to say I wouldn't do this with the forks on the bike. I know it's a pain taking them off but it's a lot easier in the long run!

Good luck!