Its exactly like the issue here..>

http://singletrackworld.com/forum/topic/rockshox-lyrik-guru-needed

my cartridge is the RCT3 but the issue is identical, forks are Revalation and have done this from new , ive tried the same thing as described in the linked thread..has anyone else has had the same weird problem..

EHM

Mine was/is on a mission control damper. I changed no parts, all I have done over time is take a little fluid out the damper to get full travel.

I serviced the fork at the weekend with no issues. Still had fluid in both lowers since last service and damper had not weirdly increased fluid volume.

Never found out the actual problem but taking a few ml out the top was simple enough. Was always nervous that this increase was caused by lower lube somehow migrating in one direction into the damper, usually it is the other way round when the o ring fails on the bottom of the damper.

Do they loose travel by not being able to compress as much or do they not extend back to the full height?

Mine did not compress to full travel – damper appeared to increase oil volume to the point it hyro locked.

Hi Mr Plow thanks i had hoped you would appear as my paging thread was removed,

so does the problem still exist as in over time you loose useable travel..
i had wondered if the lower oil was getting sucked up somehow into the damper..seems unlikely .. ive just took a bit out again and hey presto full travel but really this shouldnt happen none of my other RS forks do this nor any of my mates…

Did just opening the top cap and not removing oil work and then closing the cap again…i suppose if that works its air getting in somehow..really really very odd this..

EWM

I Ache im same as Mr Plow…they fullt extend

let air out it wont compress fully, take oil out fitt cart full travel..a few rides later remove air compress 20mm less travel ..open moco top cap compress full travel..very frustrating..

Is there something wrong/blocking the oil return ports in the compression damper? This would stop oil migrating down making it look like there was magically more oil in there. If the Mi/MoCo section is full of oil there could be air below it and under compression this could cause the forks to lock out.

not sure they perform great just over a few rides loose full compression but you may be right..

maybe next time i should lift the cart out not remove oil then replace it this would i guess point to air getting in somehow

No idea but even TFTuned guessed that I had over filled the damper oil on inspection when it was them that did the previous service. It is black magic!

Mine have been happy for a while as they are. It is all a little odd and may be in the way the damper bleeds/does not bleed when you pull it out when changing the damper oil.

Odd that it may be getting overfilled at service, then works fine to start with then degrades slowly.

What I would suggest is next time they go wrong drop the lowers off and then remove the rebound assembly BEFORE the compression assembly. Be careful to keep the forks upright during this and not to compress the rebound assembly. This will show if there is much oil in between the compression and the rebound, pour this into a pot/jug of some sort. Then invert the forks and remove the compression assembly allowing the rest of the oil to pour into another jug.

You can then compare both jugs and see which has the most oil in. Under normal circumstances the first one should have around 90% of the oil in it.

mmmm cheers… im sending them back tommorow….fork is only a month of use…

there must be a mechanical reason for this there just has to be my guess is the damper is faulty as ive not serviced mine only took oil out to get them to get full travel so its definatley in the damper upper side thats the problem probably the damper itself somehow blocking out the movement to full travel after a few rides…

argghhhhhhhhhhhh

thanks I-ache..

i just cant see how they would get full travel with too much oil in the lower legs, as they cycle through fully with the damper cart out, if oil was in the lower leg hydro locking it, it would still do it with the cart out..i think..thanks for trying to help tho ..much appreciated..

I don’t think you have too much oil in the lowers I think you have just the right amount in the uppers but it is in the wrong place.

Under normal circumstances if you remove the compression cartridge with the fork otherwise assembled properly, fitted to the bike and upright in a riding position. There should be very little oil in the top of the damper.

This is the RCT3 damper on the left, when you remove it from the top of the forks only a few ml of oil should be above the seal at the bottom of the black bit. If you have upwards of 20ml in there the oil isn’t returning properly. The air above it will be compressed slightly causing the travel reduction in the same way as the rebound seals going causes a hydro lock.

ahhhh right i see what you mean..that would make sense..thanks..im sure its something to do with the cart but i have to sent the entire fork back for warranty, i had hoped i could just send the cartridge in for repair or replacement but fisher say send the whole fork..grrr..

any idea what would cause the oil not to flow back down …

Thanks again

Blocked ports would cause it not to return, maybe some dirt has got in there or a bit of swarf from manufacture had somehow got left in there.

Mr plow, did you ever try unscrewing the MiCo and simply doing it back up? If so what happens?

Also have either of you ever had the fork hiss when you unscrew the top cap? A bit like when you tap a tyre valve.

Never noticed a hiss..

arghh my head..so how would oil go one way into the damper and not back the other way if it was blocked..

i wonder if the above the blue bit they are the holes and when its should return the black bit above is slippin down covering the holes,,

Cheers I-Ache my head certainly does now.. 👿

i think your onto something here its all it can be really theres not much else in there..

ta

The blue bit is the bit that does the damping. It has two sets of ports, both only let the oil through one way. The first set let the oil go upwards through a stack of shims that provide the damping. The second set of ports let the oil flow back down as the fork extends. Its the second set that I think may be, at least partially blocked.

I am trying to find a picture that demonstrates this.

Yeah, tried that and stuck a tywrap down the seal to see if there was any funny trapped air goings on – nothing. Just magic oil, but maybe it is an oil return issue between the dampers.

I will keep an eye on it just now as it is currently all good. It seems to be happy running a slightly lower than book, oil volume. 🙂

EhWhoMe, have a look at this it might help you understand it a little more.

How Front Suspension Works

I’ve had this issue with Revelations when I hadn’t emptied the whole of the damper side during a service. I’d taken the top off, let all the oil out and refilled. Suddenly it was hydro-locking.

What I needed to do was, after emptying the oil from the top of the damper leg, cycle the rebound rod a few times and a load more oil came out. You don’t need to remove the rod completely (it’s a bit of a PITA to get it back in) but you DO need to take the lowers off to do this which was my mistake.

As you say, there’s just a bit of extra oil (15ml or so, at a guess) that resides under the rebound disc at normal fork extension. If you don’t remove this and simply add the standard 134ml at the top end then you essentially overfill the damper.

That may or may not be the problem for you, but I thought I had the same symptoms as you, turns out I was just doing the service a bit wrong.

Thanks

I see what your saying, the final oil level is not returning , i just wonder if the oil was not returning then would the fork then not lock and and not return to its full extension

a bit like when the fox rear shocks hydro lock..you may be right tho its seems the most likely and its definatley to do with the damper..

cheers

i just wonder if the oil was not returning then would the fork then not lock and and not return to its full extension

This is the bit that I am struggling with to be honest. I suppose it depends on the strength of the spring compared to the strength of the seals in the damper. The rebound seals could be letting in air if the spring is strong enough. To be honest I don’t know and couldn’t without stripping down the forks myself.

As for the fox shock reference, that was to do with them packing down because an air seal was damaged/rubbish and air was migrating from the positive spring into the negative.

I-Ache

do you work in bike trade you seem very knowledgeable..

TA

No, I just like taking things apart. Thanks tho.