RS Fork service manual discrepencies

hard-rider

A bit of background. On and off for the last month or so I've been trying in vane to sort out my Recon Solo Air SL with turnkey (remote activated). The initial problem was that the fork stopped compressing so I decided to do a full seal and oil service. The service didn't fix the problem. The fork will now compress if pushed down slowly but if pushed quickly it locks as if the lockout is on. Flipping the lockout on or off makes not difference.

I've stripped the turnkey compression damper and found nothing wrong with it - well that I could find. It's a simple port orifice system with a disc valve on the front. Before I spend €50 on a new compression damper I want to be sure it is the actual problem. This led me to start looking at oil levels which brought to me the oil volume discrepancies in the RS service manuals.

My fork, I believe, is a 2009/2010 (s/n 47T90051201) and the 2009 manual says to use 120ml 5wt oil in the right upper and 15ml 15wt oil in the lowers.
Extract from RS 2009 service manual page 7.


I decided to check the 2010 manual just to compare and found the same fork with same internals but different oil volumes stated.
Extract from RS 2010 service manual page 7


Also, within the same manual it the section where they describe the damper serve they quote a different oil volume 120 vs the 115 stated above.
Extract from RS 2010 service manual page 20


So which volume is correct? The volumes differ by quite a bit between the 2009 and 2010, especially when considering how critical they are supposed to be. And what about the volume discrepancy between page 7 and page 20 in the 2010 manual?

I'm not fully convinced that the oil volumes are my problem but I want to be 100% sure before spending more money on the fork.

Any suggestions help appreciated.

nicklouse

so what year is the fork?

you need to find that out first.

The Rookie

For most people 120/115 difference (literally a teaspoon) is outside the accuracy they work to - many fork manufacturers give a wider range of acceptable values than that anyway! To be honest I doubt very much if you could tell the difference if you used either volume, and as it's pretty sure to not be overfilled so as to go into Hydraulic lock, it's probably irrelevant to your issue.

hard-rider

nicklouse wrote:

so what year is the fork?

you need to find that out first.

That's the problem. The fork came on my 2010 Scott Scale so I would assume it's a 2010 but how can you confirm for sure? I can't find any way to identify the model year of the fork on the SRAM site.

And with regards to the oil volume discrepancy on page 7 and 20 of the 2010 manual what would you go with?

hard-rider

The Beginner wrote:

For most people 120/115 difference (literally a teaspoon) is outside the accuracy they work to - many fork manufacturers give a wider range of acceptable values than that anyway! To be honest I doubt very much if you could tell the difference if you used either volume, and as it's pretty sure to not be overfilled so as to go into Hydraulic lock, it's probably irrelevant to your issue.

Thanks beginner. I am pretty sure the oil volume is not the cause of my problem either, but I just wanted to be 100% that I have re-assembled the fork bang on spec with the volumes to eliminate that. I guess I'm looking at a new compression damper because what else can it be if it's not the oil volume or seals?

hard-rider

OK, this is the last post on this subject hopefully. Following on from my post earlier today with regards to the problem I'm having with my fork I did some more investigating and would like some opinions on my findings.

With all the seals recently renewed and the correct oil levels the fork will only compress if pushed down very slowly. If I push fast it locks hard even though the lockout is in the unlocked position. I suspect I'm getting a hydraulic lock. So I decided to play with oil levels and so drained the oil and started with 50ml. The fork cycled normally - as expected. I the added oil in 10ml increments and it cycled fine until I got to 80ml of oil in the leg (120ml is the quoted spec). The fork will compress about 50% then locks hydraulically. It seems that when the fluid is pushed up by the damper piston and hits the bottom of the compression damper it creates a hydraulic lock as the oil will not pass through into the compression damper. To test further I removed the metal disk (shown under the spring in the photo below) from the compression damper (so effectively removing any restrictions) and the fork will then cycle fine even after I top the oil back up to 120ml. The rebound adjustment works as normal but obviously no lockout.


So my question is whether this is conclusive enough to point to the compression damper being faulty?

My compression damper has a number moulded on the side (4312-674) Is this supposed to be some sort of part number? It doesn't seem to exist in the part catalogues? The compression damper number from the catalogue is 11.4015.246.000 or 11.4015.442.030 depending on whether I have a 2009 or 2010 fork which I'm yet to determine.

nicklouse

so back to the start.

how was the fork before you did anything to it?

hard-rider

The fork just stopped compressing. It was as though the lockout was permanently on. After asking here I was advised to do a seal and oil service. I did a full seal service and everything else looked fine inside. But unfortunately the service did not resolve my problem. So I left it for a while but have now started to try figure out what is wrong and fix it properly.

The Rookie

Does sound like the compression damper is FUBAR, send it to someone who can repair, or just replace.

hard-rider

Thanks, I thought so. Don't know any one here that can repair a compression damper. All the LBSs send the forks to the main importer for service and it's 2 weeks turn-a-round. I found a replacement in Germany for €31 so may just replace it.

BTW, I found out how to decipher the serial number on the fork if anyone is interested.
The serial number takes the form of XXYZAAAAAAA where
XX = Week of manufacture
Y = Production place / factory (for example T for Taiwan)
Z = Year of manufacture (eg: 6 is built in 2006)
AAAAAAA = sequential number

supersonic

Do you use the lockout often in normal use?

hard-rider

I tend to use it a fair bit. I like to lock the fork when on smooth tarmac or climbing while standing up so the fork doesn't pump up and down. Also on long fast downhill descents on the road I lock the fork to prevent it diving if I have to brake hard.

Mostly I just like everything to work properly on my bike

supersonic

I'd be tempted to upgrade to a motion control damper.

hard-rider

supersonic wrote:

I'd be tempted to upgrade to a motion control damper.

I did think of the possibility of upgrading the damper but to be really honest I'm not sure what the MC damper is or does. I assume it does more than just lockout.

Also, I'm not sure if the remote part would work. The actual poploc lever has the same part number but the remote spool (the little pulley around which the cable goes to turn the damper) has a different part number. Looking at the manual levers they have the same part numbers for MC or TK dampers so perhaps it's the spool diameters are different between the two.

supersonic

Motion Control is a lot better made, and offers infinite adjustment of low speed compression damping. This allows a lot of tuning scope and, when precisely set up, you may not even use the lockout at all! I wouldn't use the poplock with it as you lose this fine adjustment.

A better component throughout really.

hard-rider

Thanks SS.

MC sounds like a good piece of kit. Looking at the parts list document for my fork it's not clear if the crown adjuster does the lockout and compression settings, i.e. it firms the compression progressively until it locks the fork or if there is a separate compression adjuster (the little silver wheel) as shown in the photo here. That small silver wheel is not shown in the parts list so I assume it's a simplified MC damper.

supersonic

Yep, it progressively winds on the damping until the compression port is fully covered. But there is a blow of mechanism if a suitably large sized hit is encountered. This is a simplified version as the floodgate blowoff is non adjustable, it is factory set.

Still a great piece of kit though as the compression adjustment is often all you need, set and forget.

hard-rider

Thanks. Just need to find a source for the damper now. None on ebay at the moment. It doesn't seem like a popular part. Plenty of other MC dampers listed everywhere just not the one for my model fork.