garyc Posted November 11, 2009 Report Share Posted November 11, 2009 hello, I have recently noticed that my front forks are quite springy. They are clearly underdamped compared to other newer forks on other bikes. They're the standard paioli forks on a 07 Sherco 290 and have separate compression and damping legs. I put new 5 wt. oil in it 4 or 5 months ago and I took out just over 300 ml from the damping leg when I checked just now with the oil looking ok. The damping adjuster seems to make little difference. Has anyone experienced with any modern trials forks before? Does anyone have any ideas why they seem to have lost there damping? Is there some internal seal or valve that might need replacing? Thanks Gary Quote Link to comment Share on other sites More sharing options...
copemech Posted November 11, 2009 Report Share Posted November 11, 2009 hello,I have recently noticed that my front forks are quite springy. They are clearly underdamped compared to other newer forks on other bikes. They're the standard paioli forks on a 07 Sherco 290 and have separate compression and damping legs. I put new 5 wt. oil in it 4 or 5 months ago and I took out just over 300 ml from the damping leg when I checked just now with the oil looking ok. The damping adjuster seems to make little difference. Has anyone experienced with any modern trials forks before? Does anyone have any ideas why they seem to have lost there damping? Is there some internal seal or valve that might need replacing? Thanks Gary Never heard any reports on this, yet a thorough inspection may be recommended. The damping unit can be removed. Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted November 11, 2009 Report Share Posted November 11, 2009 The first thing I would check is the oil height, unscrew the top cap and measure the oil height, this is done with the fork leg bottomed out (fully down) and you should have a 60mm air gap to the top of the oil (this is for the right hand damping leg only). Quote Link to comment Share on other sites More sharing options...
garyc Posted November 11, 2009 Author Report Share Posted November 11, 2009 Thanks I'll check the height when I refill it. The Sherco manual, http://www.sherco.com/service/2009manual_ST-2T.pdf says 330cc and 150mm air vol. is this incorrect? should it be 60mm? that could be the issue. I took out a little over 300cc so I expect the air vol. was around 150mm. Also I was wondering if it is possible there was an air lock in the damper rod? When I refilled it I measured out 330cc and just poored it in the top, assuming that with a bit of use the oil and air would get to where they should be. Is this the correct way to fill them? The oil I used was new, but had been sat in the bottle for a few years on my shelf, can new oil degrade over time all by itself? Cheers Gary Quote Link to comment Share on other sites More sharing options...
trialsnutterman Posted November 11, 2009 Report Share Posted November 11, 2009 Yeah the manual you have linked to is incorrect for your bike, the amounts and levels quoted are for the 2001 to 2005 front forks. Oil level on right leg: 60mm With forks at bottom Qty 370cc Oil level on left leg: 110mm With forks at bottom and without spring Qty 385cc There's a damping rod in the right fork leg that will still be full of oil, you'll have to take it out to drain it properly and it takes a while to get the majority of it out, I don't think you will ever get it all out. When refilling it's better to use the specified oil height measurement then it doesn't matter if you get all the old oil out. Quote Link to comment Share on other sites More sharing options...
garyc Posted November 11, 2009 Author Report Share Posted November 11, 2009 Thanks, I'll try that and see what happens. I did think it was strange that the quantities were the same as for the old style fork. Where did you find the correct amounts? I'm guessing that the height mesurement is from the oil surface to flush with the top of the fork with the cap off? Cheers Gary Quote Link to comment Share on other sites More sharing options...
stork955 Posted November 11, 2009 Report Share Posted November 11, 2009 Gday, yes, that is the way you measure oil height -with the leg compressed fully. You also need to pump the leg a few times until the internals are bled out, you will notice the level dropping while you do this until it settles down, and then take your measurement. It may well pay to completely dismantle the legs so you can clean them properly. I believe the later bikes like yours use a cartridge type of damper and these typically get full of rubbish which can effect damping. A complete strip will let you clean and flush the internals properly with solvent (kerosene etc. )It also pays to lubricate all the adjusters with grease to prevent seizing later on. Don't for get to lube the fork seals with some grease also on re-assembly, then you have a clean slate to set oil levels and adjust damping settings etc. Cheers, Stork Quote Link to comment Share on other sites More sharing options...
copemech Posted November 12, 2009 Report Share Posted November 12, 2009 Damn, I should have put two and two together on that, as the others statat the 330ml spec is incorrect for that year model. Bottom line is you need to remove the damping unit to hand pump all the old oil out, then you can go back with the stated quantity at 370ml , work the leg a bit to get the air out of the damper and all should be fine. As I recall, I had a bit of a problem with the airspace measurement thing, cannot recall exactly why but something to do with the rod attached to the cap or summat, but no matter as if youget it all out, you can put it all back correctly with the standard quantity and work it a bit to expell the air, then cap it! Quote Link to comment Share on other sites More sharing options...
garyc Posted November 15, 2009 Author Report Share Posted November 15, 2009 I've cleaned and put new oil in using the heights given and they're much better. It took a long while to work the air out of the damper though! I wonder if before, as well as there being too little oil, some air got trapped because the damper rod never got pumped it's full range in normal use. I've found though to stop them oscillating a bit on rebound I've had to wind the damper screw all the way in. I'm pretty sure it's set to nearly all the way out as standard, but this gives too little damping for my forks. Is this what other people have found? I've also upped the preload to stop them sagging, but I guess this is common in older forks that the springs have got a bit shorter over time? Cheers Gary Quote Link to comment Share on other sites More sharing options...
copemech Posted November 15, 2009 Report Share Posted November 15, 2009 I've cleaned and put new oil in using the heights given and they're much better. It took a long while to work the air out of the damper though! I wonder if before, as well as there being too little oil, some air got trapped because the damper rod never got pumped it's full range in normal use.I've found though to stop them oscillating a bit on rebound I've had to wind the damper screw all the way in. I'm pretty sure it's set to nearly all the way out as standard, but this gives too little damping for my forks. Is this what other people have found? I've also upped the preload to stop them sagging, but I guess this is common in older forks that the springs have got a bit shorter over time? Cheers Gary All I can tell you without being there is I run the damper screw at 3 clicke in from all the way out. Not a lot of damping, just some. I would guess the static sag(weight of bike only) to drop the front about 1 inch, and same for the rear, although I have had to tweak it up a couple of times. Quote Link to comment Share on other sites More sharing options...
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