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  1. #1
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    UK trail bike. The story of an XCT5.

    After messing around in the test area to get my post count up I can start a thread on my new(old) frame. The last time I visited mtbr was in October 2011!



    I bought this in a private sale after seeing a listing on ebay. I think the seller is a user on here, and the deal included some raceface cranks and a seatpost, I suspect I will move them on just now. I built the bike up for now with donor parts from a couple of my other bikes, and will upgrade to more suitable parts in time. The forks i have fitted, Reba rlt's are a little short and this puts alot of weight on the front, this is the first and most important change i need to make.

    In the meantime I have stripped the Curnutt shock as the rebound adjuster didnt seem to make any noticeable difference. upon stripping it I found that the return spring had moved and was no longer pushing on the needle so the settling was stuck on full slow.



    I made a call to the UK importer of the bikes to order a seal kit but they won't sell me one, apparently I need special tools to strip and reassemble the shock. Which I do have. I will try the italian importer to see if they are more helpful......

    Failing that, I will have to source all of the different seals separately, but this shouldn't be a problem. Just don't fancy having to buy ten of each size.

    More as it happens.

    Edited for clarity...
    Last edited by kanerdog1x1; 01-23-2013 at 03:59 PM.

  2. #2
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    A little bit of a back story. I spanner for a few people, a couple of racers, one of which has now gone onto world cup dh events, and a few years ago both of these racers were on DHS mono's. The first Foes frame they had were '06 mono's, and they were fantastic, if heavy bits of kit. They pedalled like nothing else I have ever ridden, neither before or since. I always promised myself that whenever I saw a XCT4/5 on the trail that I would ask the owner for a short ride on it, as I was convinced that this was the bike for me.
    When the later DHS frames arrived with the air shocks, although they were lighter they didn't seem to have that 'something' that the previous coil shock frames had.

    These are rare machines in the UK and I had not seen one on the trails, and they very rarely show up on ebay or in the classifieds so when I saw this on ebay, I knew it was for me. This could very well be my dream bike.

    Having spent the day that it arrived in the post looking adoringly across the workshop at it, as soon as I finished work the strip of the Cotic donor bike began. The strip and build took about two hours, and I rode the bike home, in the dark but was less than impressed.

    The shock seemed to be lazy, and the rebound dial made no adjustment at all, being stuck on full slow. Not a good first impression, but a quick search on Google led me here to the thread that explains how easy the shocks are to service. I had never had one apart before, we used to use Guido in italy for service, and he was amazing. The shock was fairly easy to take apart, just a couple of special tools needed to fully strip the main body and remove the shaft from the bottom clevis. This evening the bare aluminium parts were polished and ball burnished and are ready to refit. 2.5wt oil is ordered and should be with me tomorrow.




  3. #3
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    Quote Originally Posted by kanerdog1x1 View Post
    A little bit of a back story. I spanner for a few people, a couple of racers, one of which has now gone onto world cup dh events, and a few years ago both of these racers were on DHS mono's. The first Foes frame they had were '06 mono's, and they were fantastic, if heavy bits of kit. They pedalled like nothing else I have ever ridden, neither before or since. I always promised myself that whenever I saw a XCT4/5 on the trail that I would ask the owner for a short ride on it, as I was convinced that this was the bike for me.
    When the later DHS frames arrived with the air shocks, although they were lighter they didn't seem to have that 'something' that the previous coil shock frames had.

    These are rare machines in the UK and I had not seen one on the trails, and they very rarely show up on ebay or in the classifieds so when I saw this on ebay, I knew it was for me. This could very well be my dream bike.

    Having spent the day that it arrived in the post looking adoringly across the workshop at it, as soon as I finished work the strip of the Cotic donor bike began. The strip and build took about two hours, and I rode the bike home, in the dark but was less than impressed.

    The shock seemed to be lazy, and the rebound dial made no adjustment at all, being stuck on full slow. Not a good first impression, but a quick search on Google led me here to the thread that explains how easy the shocks are to service. I had never had one apart before, we used to use Guido in italy for service, and he was amazing. The shock was fairly easy to take apart, just a couple of special tools needed to fully strip the main body and remove the shaft from the bottom clevis. This evening the bare aluminium parts were polished and ball burnished and are ready to refit. 2.5wt oil is ordered and should be with me tomorrow.



    nice! I like the polished bits. Your british'isms are a bit hard for us yanks to follow, though.

    looking forward to seeing the bike built.
    Stupid, but sometimes witty. Occasionally brilliant. Slow and fat though.

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  4. #4
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    Hello Kanerdog, they do look nice polished, i had one for a coupla years, its an ideal uk do it all bike imo, please post a pic when its built up, next to your ktm!

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    Aha! Cheers guys.

    It was your thread 'iheart' that convinced me to strip the shock, Thankyou.

    And 'forgot', no KTM atm, it has been a couple of years since I had one. I made the move to road bikes a couple of years ago, but occasionally get the itch for an enduro bike so possibly in the future....


    I have reassembled the shock for the most part, but could not complete it as the oil hasn't yet arrived. It was difficult to get the rebound needle to move freely, in the end I took a stronger spring from a ball point pen, and this helped. With no seal and no lube the needle moved freely, but as soon as the smallest amount of friction from the oring and lube were present, it would stick in the closed position. Roll eyes smiley.

  6. #6
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    You're going to love this bike once you get the shock sorted out. I have one, orange no less, but with a Ti coil on my Curnutt shock. Like you said this bike pedals like nothing else I have ridden and it's just a blast to ride. Good luck and keep us posted on you progress!

  7. #7
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    no ktm, ahh thats a shame, they would look v nice next to each other.

  8. #8
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    Cheers guys.

    The bike is now reassembled, no drama bleeding the shock but the oil level was a complete guess. I have set it at 10mm which is probably on the high side. Can anyone tell me what it should be, I assume it is measured with the shock compressed onto the bottom out bumper?



    Also, having searched the web for info on springs I am surprised to read that I have the correct spring for my weight, but it sags way too much, and becomes coil bound only halfway into the travel! Perhaps I need a ti spring?....

  9. #9
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    Quote Originally Posted by kanerdog1x1 View Post
    Cheers guys.

    The bike is now reassembled, no drama bleeding the shock but the oil level was a complete guess. I have set it at 10mm which is probably on the high side. Can anyone tell me what it should be, I assume it is measured with the shock compressed onto the bottom out bumper?



    Also, having searched the web for info on springs I am surprised to read that I have the correct spring for my weight, but it sags way too much, and becomes coil bound only halfway into the travel! Perhaps I need a ti spring?....
    I measured the IFP depth on mine, with the shock empty. But I didnt get it perfect the first time ,and had to re-do it.

    What is the stroke on your shock? Not sure if my measurements will work for yours or not.
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  10. #10
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    Quote Originally Posted by iheartbicycles View Post
    I measured the IFP depth on mine, with the shock empty. But I didnt get it perfect the first time ,and had to re-do it.

    What is the stroke on your shock? Not sure if my measurements will work for yours or not.
    here's my original thread. Rebuilding a Curnutt Shock

    I didnt have any directions from Foes, so I had to figure out the IFP depth myself - and I took two tries to do it.

    The good news, is you shouldnt break anything if you're careful - so go for it. Here's all I did to find the starting IFP depth.

    rebuild your piston

    rebuild the shock body

    Either depress or remove the schraeder valve internals - the way the IFP can move freely in the shock body - without air pressure causing any affect.

    Insert the IFP into the shock body

    Use the piston to push the IFP all the way into the shock body. screw the cap onto the shock body - and push the IFP all the way to the point where the shock is at bottom out.

    If the bottom out bumper gets in the way, you will need to account for this later.

    Now with the schraeder valve still depressed, or removed - reverse the process, leaving the IFP at the bottom out point. Take the shock apart, again - removing all internals, except the IFP.

    Use a pencil or something else to measure the IFP depth.

    If the bottom out bumper prevented your shock from fully bottoming out - measure the width and push the IFP down further - by this amount.

    Now to make sure that during use your piston doesnt contact your IFP, you will want additional space between the IFP and the piston.

    I recomend starting at 1/2". Go ahead and push the IFP in, further by this amount.

    Re-install the schraeder valve core. you now want the ambient air pressure to hold the IFP at its current depth.

    Go ahead and refill your shock with oil - making sure to get rid of all bubbles as you go. (cycle the piston, etc)

    you should probably leave the coil spring off for now.

    Once back together and before charging the IFP, cycle the shock to make sure everything is moving nicely and you dont have interference.

    At these low pressures and forces, you shouldnt have to worry about any burps between air and oil chambers.

    To be 100% certain you have good clearance - you might want to bolt the shock onto you bike, no spring and completely cycle the shock - all the way to bottom out. Do this carefully and slowely - as you still dont have any significant pressure holding the IFP in place.

    When you're satisfied you have clearance - pressurize the IFP (minimum 50 PSI) and put everything back together.

    You'll notice in my thread that I took two tries to the the IFP depth I liked. Once you get the hang of this, you have much more flexibilty in fine tuning your shock - you can really dial in how it ramps up, which is nice.

    Disclaimer - I'm not a professional! I just have a bunch of Foes and decided to teach myself how to rebuild my shocks. This may or may not be the best way - but it works.
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  11. #11
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    Thanks for the reply. I chose to fill and bleed the shock though the top rather than via the seal head. I should really have taken some pics, sorry. The shock is 2.5inch.

    I have put a few gentle miles on the bike, to try out different air pressures. I can tell you that the difference between 65 and 100 psi is very noticeable. Also, when climbing in the middle ring there is very little pedal induced bob, certainly a lot less than when in the big ring. I am loathe to take the big ring off of the bike as it is so stable it demands to be ridden fast. But, the spring is intrusive on the ride, I think I am only getting about 80-100mm wheel travel.

    I think I will try less air gap in the shock tomorrow to feel the difference, perhaps reduce it to 5mm.

    Can't wait to get some more suitable forks.

  12. #12
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    Well well well. Someone on another forum suggested this might be the frame that was used as a test bike at bike radar, :- Foes 2:1 XCT 5 - BikeRadar
    Upon close inspection of the images I am pretty certain it is.

  13. #13
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    I took a fone call yesterday from one of my racer buddies, he mentioned that he may have a couple of Curnutt spares on the shelf. Indeed, the stash included a longer steel spring, and it was a 450. Bingo! You can just about make out the felt pen markings:-



    You can see here clearly the tool I made to hold the shock body firmly when unscrewing the top clevis or seal head:-



    I have also set the air gap at 5mm with the shock compressed:-



    Here you can see the difference in the lengths of the springs. I had to separate the preload spacer from the preload nut to allow it to fit. I love the way these shocks seem to be modular, the top spring perch is identical to the bottom one.



    And assembled:-



    I have ridden the bike home this evening, and it feels so much better with the heavier spring. I could just get the sag correct with the first spring with four turns of preload, but it is correct with just two turns now, but feels so different. I suspect part of this is down to the reduced air gap, so next time i will try a larger gap, maybe 15mm, to feel what effect that has. My friend had a spin around his driveway to get feel for the bike, he reckoned that the rebound was too fast, I thought it was too slow! This confirms I have the correct weight oil in, the 2.5wt was a guess based on the condition of the oil taken out. I have it set now at one and a half turns out, and is a setting we both agree on.

    Really need different forks though, the front end is holding me back now.

  14. #14
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    This image I took last week, before a bit of a ride.



    You can see clearly that the forks are too short and the bike is sitting on its nose. It rode ok, but far from perfect.

    Earlier this week I ordered a set of Rockshox Revelation forks for the bike, and set about fitting them. I knew I wanted the travel reducing to 130mm, but had no idea that the supplied 10mm spacers were not compatible. I have reduced many pairs of Reba's/Rev's in the past but these were all dual air models. The new RS forks are all solo air, and require a little bit of work to shorten the travel. To reduce the travel the air spring shaft needs to be shortened by the amount of travel reduction required.



    I removed 20mm from the top end of the shaft, and redrilled the shaft for the roll pin. Once I was happy with the outcome, I decided to make a new shaft in titanium to save a tiny amount of weight but more importantly produce a very smooth and slippery shaft. The finish on the oe shaft is simply as the aluminium is drawn, and far from smooth.

    Here you can see the difference, the ti item is smooth.



    The other little mod I did was to the already fantastic new lockout lever.



    It is supplied with a torx headed bolt which makes servicing a bit of a ball ache, so I swapped out the bolt with a stainless allen head bolt. Also turned the head down on the lathe so save hardly any weight.



    And, as she stands this weekend:-




  15. #15
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    Had a proper ride this afternoon. It got dark, but that made it more fun.



    I have fitted a reverb seatpost, and I am impressed. I have played with them before but never had a full ride on one. Its the ossum. Also took the cranks form my yeti, i wanted to try the 2x setup on the 26er. i think i will leave them on here to be honest, and get some 3x cranks for the yeti....

    Also picked up some titanium hardware for the shock. Not fitted them yet, should get around to that tomorrow.


  16. #16
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    Bad idea using Ti bolts for the shock. The shear modulus of Ti is roughly half that of steel. It might be OK to install them on the links but you definitely shouldn't use them at the two contact points where the shock mounts to the bike. I used them on the shock mounting points on a Turner Burner frame only to have them snap.

  17. #17
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    Thanks for the heads up, but I don't think it will be a problem. The bolts have centres so I can check them periodically for runout and creep. If they are done up correctly, there should only be a very small amount of shear load on them, it 'should' be distributed through the frame via the shock bushes.

    The foes has a low leverage ratio, much like my old my2000 heckler has. That survived fine with m5(!) titanium bolts on the front shock mount, and an m6 at the rear. If anything, I think the foes with the m6 at the front shock mount is perfect, and the m8 at the rear is over built.

  18. #18
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    No problem...could have been that the bolts I installed were shoddy, could've been a combination of my riding style and weight (@ 220lbs suited & booted) that caused the failure or all of the above. Regardless, for me the cost/benefit - risk/reward is not there for me to justify use of Ti bolts to mount my Curnutt shock.

    In any case, I'm really enjoying this thread. Your XCT looks awesome, nice set-up. Looks like you have the Revelation on now, I didn't think I would but I really like the white fork on the orange. What travel are you running up front after your fork mod? What are your initial ride impressions?

  19. #19
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    the revs are set at 130mm now, i may possibly try 140 in the summer and when the trails get faster, but for now 130 is perfect.

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    Hose routing of these dropper posts has always been the part that put me off. I have installed a couple on friends bikes and they have always been a compromise of cable ties and heli tape. I wanted to make a proper job of mine.

    Started with a Thomson seat clamp, as this is not only the most modern design, but it uses a barrel nut in the same way as a Salsa unit. I like this idea, but the Thomson also has the floating washer much the same as the seatposts feature, full of win.

    Although the Thomson part is pretty low profile, certainly smaller than a Salsa, it still was very close to the reverb hose on the lowest setting. So i machined away a very small area, not so much for clearance as it still touches, but at least the hose won't rub the anodising off now.



    The other part is fabricated from 6/4 titanium. It is actually the second try as the first item was a bit ugly. Fitted:-



    There is still a patch of heli tape, and I will leave it on, but the hose doesnt touch the frame in any position.

  21. #21
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    I have managed to fit a couple of steady rides in this week, the light is holding on more and more as winter turns slowly to spring.



    I am also starting to become an expert at removing and refitting the shock, and then rebuilding it. It has been out of the bike for one reason or another three times this week alone......

    Lessons learned are that the IFP height should be about 10mm, this seems to make a noticeable difference to the rebound damping. With a smaller IFP volume/height, the shock had erratic damping, most noticeable in the rebound stroke with an audible 'clunk' that could be felt through the frame. Now I know that nothing could be touching inside, as it was in the rebound stroke so the piston&shaft would be travelling away from the IFP....

    Lesson two is that careful bleeding is rewarded with much better quality damping. Goes without saying, huh? The best way I found was to fill, to the brim with oil while the shock was compressed. Refit the top cap, not tight, just so the seal is working. Then extend the shock and leave for a couple of mins. This should introduce a vacuum inside the body, and make any air bubbles hidden inside the damping circuit very big, and allow them to escape. Then, after a few mins, very slowly compress the shock. A slow compression is vitally important here as it keeps turbulence in the oil to a minimum. Then unscrew the top and you should be greeted with oil free of bubbles.

    The damping is now very controlled, and the rebound adjuster makes very tangible differences to both the rebound stroke, and a little to the low speed compression.

    I really like this shock.

  22. #22
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    Quote Originally Posted by kanerdog1x1 View Post
    the revs are set at 130mm now, i may possibly try 140 in the summer and when the trails get faster, but for now 130 is perfect.
    I've been running 140mm up front from day one. Feels very balanced with the rear travel. The front stays planted on climbs, lively handling in tight singletrack, and comfortable bombing down. I started with a Magura Thor 140mm. Had some diving issues so I decieded to switch to a Fox Vanilla RLC 140mm. Coil front and rear are perfect together. Been toying with the idea of going 150mm and Ti spring with a Marzocchi 44 RC3.

  23. #23
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    Quote Originally Posted by kanerdog1x1 View Post
    Hose routing of these dropper posts has always been the part that put me off. I have installed a couple on friends bikes and they have always been a compromise of cable ties and heli tape. I wanted to make a proper job of mine.

    Started with a Thomson seat clamp, as this is not only the most modern design, but it uses a barrel nut in the same way as a Salsa unit. I like this idea, but the Thomson also has the floating washer much the same as the seatposts feature, full of win.

    Although the Thomson part is pretty low profile, certainly smaller than a Salsa, it still was very close to the reverb hose on the lowest setting. So i machined away a very small area, not so much for clearance as it still touches, but at least the hose won't rub the anodising off now.



    The other part is fabricated from 6/4 titanium. It is actually the second try as the first item was a bit ugly. Fitted:-



    There is still a patch of heli tape, and I will leave it on, but the hose doesnt touch the frame in any position.
    The shock is super simple to work on.
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  24. #24
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    Cheers guys. I love the way the shock is easy to work on too.
    And, I like the quality of Fox forks, but I dont like the price/value ratio in the UK, they are VERY expensive. IMO they don't work as nicely as a RS fork that is 1/3 the price. And I particularly don't like the feel of vanilla forks, the springs feel too linear. A friend has picked up a Marzocchi 44ti within the last couple of weeks, and I am looking forward to trying these.

    Stopped by the LBS today, which is normal for a Saturday, and came away with a bottom bracket to match the headset I bought from someone on a UK forum.



    Fitted them both this afternoon, so I am one step closer to putting the Cotic back together. Thinking about getting gold hubs too....

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    Unbelievable thread and nice touches to everything. I'm in the process of rebuilding my curnutt and haven't quite found the sweet spot for IFP depth. I really like the repeatability of your measurement from the end of the shock body to the bottom of the IFP.

    I see you've characterized a too small IFP depth (5mm) as having erratic rebound properties. What would you describe the effects of having too much IFP depth (15mm +)? I'm trying to get small bump compliance at speed more linear all though the stroke, i.e. not too much ramp up. I'd still like to tune the ramp up with the knob when a trail deems it necessary, jumps, drops, etc.

    Any help would be greatly appreciated. Thanks and great bike!

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