alan_nc Posted March 26, 2009 Report Share Posted March 26, 2009 Group, So my forks bottomed out a couple of times in the Trial this past weekend. I'm assuming the springs are old and a little weak. Planning to put some spacers in. Do I: Put in a couple of 1/16" washers or put in a 1" plug? What I'm asking is how much shimming do you do? Second part would be how do you know when you have shimmed enough? Thanks in advance. Alan Quote Link to comment Share on other sites More sharing options...
isaacely Posted March 26, 2009 Report Share Posted March 26, 2009 Hi, when adding spacers use something thin like a washer, keep adding until the front end feels a bit harder. You will know when you have added too many as the forks will top out if you lift the front end in a wheelie or go over a bump, its a case of experimenting untill you find what feels best for you. It will get harder to get the fork top nuts on as you add the washers due to the spring being compressed more, lift the bike onto a stand so the front wheel is off the ground to help get the nuts back on. I hope that helps Alan. Quote Link to comment Share on other sites More sharing options...
feetupfun Posted March 27, 2009 Report Share Posted March 27, 2009 TY250 twinshock springs are close to being coil bound when the forks bottom with the standard springs and spacers. If you add more than about 9mm of additional preload, you will get coil binding, which limits travel, and can bend the springs. I see someone advised not bothering with heavier fork oil to prevent bottoming. I would like to suggest that heavier weight oil will reduce the bottoming, as will reducing the air space on top of the oil. I suggest you add a modest amount of additional spacer length say 5mm, and carefully set the fork oil height to 125mm from the top of the tubes, with the springs removed and the forks completely bottomed. 15WT or 20WT fork oil will be fine. If you still are not happy with the bottoming resistance after doing these things, springs with a higher rate can be bought from B&J Racing in Tennessee. On another note, TY250 twinshock forks have effective anti-topping springs and will remain free of harsh topping out provide the forks have enough oil in them to provide rebound damping. They also have a very effective anti-bottoming hydraulic device so will not bottom metal-to-metal during riding provided there is enough oil in them to cover the device. Quote Link to comment Share on other sites More sharing options...
alan_nc Posted March 27, 2009 Author Report Share Posted March 27, 2009 feetup, Well tried your idea first. Seems that I didn't have enough oil in the tubes (added several cc's to bring it up to the 125mm below top). Put a 5mm or so washer in each tube and brought the level up. Seems to be working fine. Will have to do the ole wheelie over a log and come down fairly hard to see if it is truly fixed. Stayed with the ATF that I had in the tubes (I'm about 160# so don't need to much dampening). Don't have a Trial for a couple of weeks so have plenty of time to test it. Alan Quote Link to comment Share on other sites More sharing options...
jse Posted March 28, 2009 Report Share Posted March 28, 2009 feetup,Well tried your idea first. Seems that I didn't have enough oil in the tubes (added several cc's to bring it up to the 125mm below top). Put a 5mm or so washer in each tube and brought the level up. Seems to be working fine. Will have to do the ole wheelie over a log and come down fairly hard to see if it is truly fixed. Stayed with the ATF that I had in the tubes (I'm about 160# so don't need to much dampening). Don't have a Trial for a couple of weeks so have plenty of time to test it. Alan Alan, The TY has what's known as "damper rod" type forks and work well with 15/20 weight fork oil. The ATF you are using would be more suited for a cartridge type fork, like on the modern bikes, during warm weather or a heavier rider. ATF is about 7.5 weight and at 160 lbs, you should probably be running 15 weight, minimum, for them to work well. The combination of low oil level and too light fluid could be the cause of your problem. Jon Quote Link to comment Share on other sites More sharing options...
alan_nc Posted March 28, 2009 Author Report Share Posted March 28, 2009 Jon, Thanks, I agree. I have tried to find 15 or 20 weight oil with no luck. None of the auto parts stores around here sell single weight oil except 30 weight. Didn't even find any on-line. Can you point me to a source? Alan Quote Link to comment Share on other sites More sharing options...
jse Posted March 28, 2009 Report Share Posted March 28, 2009 Jon,Thanks, I agree.I have tried to find 15 or 20 weight oil with no luck. None of the auto parts stores around here sell single weight oil except 30 weight. Didn't even find any on-line. Can you point me to a source? Alan Alan, You really need to go to a motorcycle store for specific "fork oil". Fork oil has certain additives, such as one to reduce foaming (as does ATF) so that aeration does not reduce damping function (or in the case of ATF, cause hydraulic pressure variations). Jon Quote Link to comment Share on other sites More sharing options...
searay175 Posted November 30, 2009 Report Share Posted November 30, 2009 How did this work out Alan? I have a ty250c that I just aquried and there is very little dampening as the front bottoms out easily. I will start by changing the fork oil. How much does each leg hold? and what weight fork oil do you use? I weigh 160# also. Thanks! Steve Quote Link to comment Share on other sites More sharing options...
alan_nc Posted November 30, 2009 Author Report Share Posted November 30, 2009 I have been using ATF all season and it seems fine. Find Tony's posts on how much to put in each fork - it's some measurement down from the top edge. I would take the forks apart and clean everything before putting in new oil. It is just amazing how much crud is in them. Alan Quote Link to comment Share on other sites More sharing options...
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