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TOPIC: EXTREMELY stiff front suspension

EXTREMELY stiff front suspension 15 Aug 2019 02:38 #1

  • Kosmo
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Hi all. I recently rebuilt the front forks on my DT175. I had everything put back together and torqued to spec but today I noticed I can barely compress the front end. I loosened up the triple tree clamps bolts, the axle nut, the center cap bolt, thinking that maybe it's all twisted up and binding. That didn't make a huge difference. It might have been binding a little bit but there's definitely something going on....

is it a possibility I put too much oil in? Service manual calls for 146ml +/- 2ml and I filled up roughly that, mainly making sure there's the same amount in both. Should I try draining some oil from the top at this point and see if it makes a difference? Is there a chance I did something wrong and maybe trapped air inside the system? I'm just shooting in the dark at this point. It's almost 6am and I should probably sleep haha. Too poor to take an actual vacation so I've just been spending long nights building my new trail bike.

Thanks for all your help!

edit: might be worth to mention the bike these are from had a bit of an accident falling off a trailer...front end got twisted in the triple trees so I loosened up all the bolts and straightened it out, suspension seemed to be moving around okay after that and before rebuild, tubes did not look bent.. When I was filling the forks up with oil on the bench, the tubes were moving around fairly smooth inside the lowers. Part of me is paranoid maybe the tubes ARE bent.

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Last Edit: by Kosmo.

EXTREMELY stiff front suspension 15 Aug 2019 03:58 #2

  • RT325
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No easy answer to that question--well, without being there. Are you trying to compress them through holding the front brake on as that's how i do it for a good feel. I know you don't want to pull it apart now its together but i'm wondering how each fork feels individually when out of the bike--is one different to the other in feel. Then with the springs out do they--or one--bind beyond normal. I know you said they're straight but carefully hold the lowers in the vice or just hold it on the bench with the fork stanchion hanging out in mid air & then revolve it as any bend will be easy to see. If both are slightly bent i just turn them rearward equally so there's no tension on anything when tightening the axle or clamps. Any bend will be just below the lower triple clamps so won't affect smooth sliding /operating providing they're not under tension when all bolted up & wheel in etc. If the book say 146mls then you should be safe at that. Are you using thick engine oil or thin fork oil. Sorry i'm just talking to myself. & are the springs non original. Lastly, were they operating like this prior to rebuilding. Run out of ideas at the mo but have seen strange things causing binding but usually caused by crash damage, ie bent lower alloy sliders but on older yamaha road bikes in an accident--into the rear of a car straight on mostly.

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Last Edit: by RT325.

EXTREMELY stiff front suspension 15 Aug 2019 05:52 #3

  • blazeone
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I think they are pretty sensitive to oil level. Plus the type/weight. As part of my CT2 restoration I have the same concern. Rebuilt forks and added a little extra oil as they were too soft before. Might have overdone it, as mine are probably too stiff now. I haven't finished the build yet but I'm going to wait to ride and put some miles on it before draining a smidge of oil.

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Last Edit: by blazeone.

EXTREMELY stiff front suspension 15 Aug 2019 15:55 #4

  • liferbiker
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saw your pics,try removing top caps, wheel, so you can slide them up & down, loosten top clamp bolts so "trees" are free as well. if all feels ok, reassemble leaving loose, put caps on then compress (brake on) a few times they will usually find where they want to be, straighten wheel as necessary, compress a few times, if they fall out of alignment badly, you may have an issue.

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EXTREMELY stiff front suspension 15 Aug 2019 16:32 #5

  • Kosmo
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liferbiker wrote: saw your pics,try removing top caps, wheel, so you can slide them up & down, loosten top clamp bolts so "trees" are free as well. if all feels ok, reassemble leaving loose, put caps on then compress (brake on) a few times they will usually find where they want to be, straighten wheel as necessary, compress a few times, if they fall out of alignment badly, you may have an issue.


Will do, thanks everyone. I AM hoping it's just oil but I am leaving this issue for when the bike is more reassembled. Currently It looks like this and if I start taking the wheel off it'll just tip the whole frame over forward. Gonna get the rear end reassembled, get my spirits up, and then come back to the front end.

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Last Edit: by Kosmo.

EXTREMELY stiff front suspension 18 Aug 2019 18:56 #6

  • Prinzy
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The forks on my 74 dt125 and my brothers ct3 are both bent back slightly from years of off road abuse. I rebuilt both sets and on the 175 I didn’t pay attention to how I put them back in the triple trees and there was absolutely zero front suspension. I loosened them back up took off front wheel and positioned them both with the bend to the back like it originally was and they work perfectly.
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EXTREMELY stiff front suspension 20 Aug 2019 08:29 #7

  • Kosmo
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Damn...starting to think mine are bent. How did you know how to reposition them? Is the bend that obvious?

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EXTREMELY stiff front suspension 20 Aug 2019 08:49 #8

  • Scootern29
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Here's what I would check first. Loosen the front axle nut or take it off. See if there is any space between the bushing and the inside of the fork mating surface. If there is a gap it's not good. What that would mean is you are pulling the fork tubes in which makes the distance of the lowers shorter than the triple clamps which will make them bind. Use a washer to take up the gap if there is any.
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EXTREMELY stiff front suspension 20 Aug 2019 08:53 #9

  • Prinzy
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Yeah it’s probably at least 1/4 inch bend but yours look like there bigger forks idk

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EXTREMELY stiff front suspension 20 Aug 2019 09:03 #10

  • Kosmo
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Scootern29 wrote: Here's what I would check first. Loosen the front axle nut or take it off. See if there is any space between the bushing and the inside of the fork mating surface. If there is a gap it's not good. What that would mean is you are pulling the fork tubes in which makes the distance of the lowers shorter than the triple clamps which will make them bind. Use a washer to take up the gap if there is any.


Hey, thanks for the info, I am just confused as to what bushing you are referring to?

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