I'm a noob. please help bring my childhood st90 back back to life. - rear shocks

Discussion in 'CT90, CT110, ST70, ST90 Discussion' started by Drew_P, Dec 1, 2020.

  1. Drew_P

    Drew_P New Member

    Joined:
    Nov 19, 2020
    Messages:
    16
    Likes Received:
    3
    My st90 got me through jr high. I loved that thing. But it was already 25 years old at that time. Then it broke and sat in a barn for 25 more years. Now my son is approaching that age, and I'm fixing it up for him. I got it running, mostly cleaned up, and it's a blast. Though it still needs work. Specifically the suspension is......soft. fFor the front end, I know what to do. I am in the process of replacing the fork seals and will refill the oil. For the rear, is replacing the shocks with stiffer shocks a thing? My central strut the coil spring goes over also has a hole worn or rusted through in it. I see that dratv has rear shocks that are stiffer and longer. Supposedly to raise the bike. I don't want it raised, just a little stiffer. Does anybody know of a decently priced shock that is the same size but a little stiffer?
     
  2.  
  3. scooter

    scooter Well-Known Member

    Joined:
    Aug 28, 2009
    Messages:
    1,447
    Likes Received:
    327
    I'm not a big proponent of the need for stiffer shocks. My opinion is that a properly functioning shock should do just fine. An equivalent shock with similar spring rate may be all you need.
     
  4. Drew_P

    Drew_P New Member

    Joined:
    Nov 19, 2020
    Messages:
    16
    Likes Received:
    3
    and I'm mostly fine with that. I just don't know anything about shocks beyond they compress and are bolted on on both ends. How would I determine what length and stiffness I would need?
     
  5. b52bombardier1

    b52bombardier1 Well-Known Member

    Joined:
    Dec 26, 2010
    Messages:
    2,053
    Likes Received:
    207
    I put a set of shocks from Dr ATV on one of my CT90 bikes and I have been very happy with it. Its not like we have many choices here for length, stiffness and spring rate for our 50 year old bikes.

    I'd take that $60 chance again on that set of Dr ATV shocks even though it says they are for a CT90. Email Jack and ask him about the fit for an ST90.

    http://dratv.com/ctchreapstoe.html

    Rick
     
    scooter likes this.
  6. scooter

    scooter Well-Known Member

    Joined:
    Aug 28, 2009
    Messages:
    1,447
    Likes Received:
    327
    Length is measured with the shocks off the bike from center of bolt hole to center of bolt hole. As far as actual spring rate, I think those springs are progressive (meaning spring rate can vary with displacement). I’d just look for something that says they are applicable to the ST90 but if you need a number probably something around 85 lbs/inch for the smaller of the two rates. You might see a spring rate quoted with a slash between two numbers - they are the smaller and larger rate if the spring is progressive.
     
  7. DAX-IT!!!

    DAX-IT!!! Member

    Joined:
    Sep 23, 2020
    Messages:
    79
    Likes Received:
    17
    You could try and find a place that reconditions motorcycle shock absorbers - you might pay a bit high on the price but if you want to keep it as it was and not risk taking chances on uprated/stiffer springs etc., it might be an idea worth pursuing; i'm sure there's a place over there in the States that must do that kind of thing - man, you can get anything in the USA....................... WELL, ALMOST !! :cautious:
     
  8. kirrbby

    kirrbby Well-Known Member

    Joined:
    May 28, 2009
    Messages:
    10,633
    Likes Received:
    1,810
    If you decide you want to try these shocks that b52bombardier1 linked above, I have a set, that I'd sell cheap. They were way too stiff for me on a CT70. I'm 165lbs. Mounted them, then removed them. Basically brand new.
    They might not feel as stiff on a ST90..? But I would imagine that they'd be similar, since it's a similar bike.
     
  9. scooter

    scooter Well-Known Member

    Joined:
    Aug 28, 2009
    Messages:
    1,447
    Likes Received:
    327
    I believe those shocks are very similar to a set of CT70 shocks and my tooling should should fit to do a rebuild if you want to keep the bike original.
     
  10. farm dog

    farm dog Member

    Joined:
    May 3, 2014
    Messages:
    206
    Likes Received:
    23
    They are 330 I believe.
     
  11. Drew_P

    Drew_P New Member

    Joined:
    Nov 19, 2020
    Messages:
    16
    Likes Received:
    3
    I appreciate the offer. I finally got the front forks rebuilt and haven't had a chance to try it yet. I also have to keep in mind that ultimately this bike will be my kids and nephews not for me. But I'll keep you in mind.
     

Share This Page