Hi all, I'm going to refresh the rear suspension on my '87 GPZ500.I've bought a 2nd hand linkage off ebay which will be here soon (figuring the bushes in mine will be stuffed after 24 years).However buying a 2nd hand shock is not as cheap.
Therefore my question is - when I remove the linkage and shock, what can I do to test the shock to see if its working ok or not!
Any help appreciated
doriandarby,
Apr 20, 8:16pm
The shock has preload only.The rear of the bike just feels "odd" when riding, doesnt give a lot of confidence.Because the unitrack setup doesnt have any grease nipples on it I'm kinda thinking that I'll need to sort that bit out as well as any shock issues.
To test the damping, would I do the same as on a car and give the bike a big push and see if it comes up once then stops bouncing!
gunhand,
Apr 20, 10:04pm
If I was you and your serious about getting a good set up I would be looking at someone who sets up race bikes (and wins) or a supplier of rebuilt or custom made shocks. I dont pretend to understand suspension on a bike and from what Ive read alot dont. It would appear to be quite a science. But being an older bike there wont be alot to it. Although you should have the option of doing a modern upgrade. Have a look in BikeRider or Kiwirider mags. Bikerider has hadquite a bit about suspesion of late and probably has contacts for suppliers. If you want to go top of the line or seek quality advise emailohlins@crownkiwi.co.nz.
doriandarby,
Apr 20, 10:26pm
Thanks for that. I phoned up a local bike shop that has the skills to strip and rebuild a shock - they want around $300 to do it.There is a brand new shock on ebay thats within my budget, I might get that next month when I have more money.
321mat,
Apr 21, 1:38am
Chain tension also can have an effect on handling in the way you're describing.
gunhand,
Apr 21, 2:08am
This is a 24 year old bike and unless its been maintained to a high degree there will quite abit needing done to the rear to make it handle as with the front end. No much point doing one without the other if you want it to handle well. Probably everything suspension wise will be worn out and need rebuilt or replaced. What are you going to do with the bike when sorted! Luckly older bikes have narrow tyres and dont sqaure off as much as the new wide things seem to. Ive seen wide tyres that flat in the middle you could dam near do away with the stand. Itll take alot of time, patients, no how and testing to get a bike to handle well.
doriandarby,
Apr 21, 2:22am
I'll be keeping the bike as its my daily commuter. I'm pretty happy with the fork performance as I recently rebuilt them.
WHen I had the forks off I didnt notice any play or notchiness in the head bearings, might leave those alone for now.
I'll check the swingarm bearings.I might also be tensioning the chain a bit too tight, will get out the ruler later and see what the deflection is.Yep, its on old crappy, cheap bike but I like riding it and doing my own maintenance on it.
Still going to replace the unitrak linkage (its on its way from the US now, might as well!) and have a long hard think about the shock absorber.
Currently running 32pi in the front, 36psi in the back - on BT45's
mantagsi,
Apr 21, 7:55am
Sadly suspension on bikes is probably the most misunderstood subject, and no offense but if you aren't sure exactly what you are doing (ie; if you change something, are you confident you know what will be affected, why and how!) - I gotta agree with Kaz, if there is one thing it might not hurt to take to someone who does it for a living, it is a bike suspension job. Good luck either way :)
doriandarby,
Apr 21, 8:33am
Understand your point, but I'll be replacing worn out parts with newer ones from the same model of bike.At least then, any suspension changes I try will be performed on parts that are not as old and knackered as they could have been.Anyway, I'm looking forward to the challenge of working on the bike and seeing if what I do is for the good, or the bad.Good thing I have medical insurance :)
321mat,
Apr 21, 11:07pm
That's actually quite high tyre pressures, which could be making the ride quite harsh.
I would suggest maybe 26 in the front and 30 in the rear. This will also allow the sidewalls to flex a bit more, and take some of the stiffness out of the ride. You are using crossply tyres, aren't you! These models were developed to run on crossply, not radial tyres.
doriandarby,
Apr 21, 11:19pm
Yep, using crossply Bridgestone BT45's
I'll try lower pressures, maybe 28psi front 32psi back (quoted from manual)
smac,
Nov 26, 10:19am
One other thing to consider, which 321mat has sort of touched on: is this something that has happened over time! Or has it always been like this!
Some bikes feel just plain weird when they ARE set up right ad/or are new. Are you sure you're not looking for a problem that doesn't exist!
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