Author Topic: Best test for rear shocks?  (Read 2501 times)

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Offline Hush

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Best test for rear shocks?
« on: June 13, 2009, 12:48:35 AM »
I've been toying with the idea of buying some new rear shocks for the old 650 but want to be sure I'm not replacing ones that still have some life in them.
I've had the rear end "bottom out" on me at speed when I've hit a hole in the road, is that a fair indication?
Seen some advertised fairly cheaply ($75 US) on the net, getting them locally is impossible as the bike shops charge like wounded bulls in NZ.
What is the proof positive way of telling if my old shocks are screwed?
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline Pinhead

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Re: Best test for rear shocks?
« Reply #1 on: June 13, 2009, 12:57:08 AM »
I was contemplating the exact same question today at work. My question is, IF the shocks do have some life left in 'em yet, how much of an upgrade would new ones be? Has shock tech changed that much in 30 years?  ???
Doug

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Offline Hush

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Re: Best test for rear shocks?
« Reply #2 on: June 13, 2009, 01:45:31 AM »
I've seen these on Parts'nmores' net site, they look fairly standard and even converting to NZ currency would make them cheaper than offered by local bike shops.

Black classic type shock body with 4 position spring preload adjustment. Progressive heavy duty chrome springs. Includes bushings, inserts, washers and spring preload wrench.
335mm (13 3/16") Eye to Clevis

 
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline Hush

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Re: Best test for rear shocks?
« Reply #3 on: June 13, 2009, 02:02:25 AM »
These are the Dave Silver ones and they look exactly same, they cost 65 pounds.
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline manjisann

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Re: Best test for rear shocks?
« Reply #4 on: June 13, 2009, 04:11:02 AM »
+2 on wanting to know this. I'm just starting the build on my 650, and while I want to repair or replace anything that is unsafe, I've already blown my budget sky high so if I can put off replacing the shocks till next season or so, that would be best. Also, is it possible to rebuild the original ones? Just wondering, I don't mind work as long as it a) is safe and b) saves money.

Brandon
Sure it's for sale! How much you ask?? Well, how much are you willing to pay??? Now triple it, that's the price!

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Offline Triffecpa

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Re: Best test for rear shocks?
« Reply #5 on: June 13, 2009, 12:00:44 PM »

Shocks only do two things.  Firstly they hold the springs in place.  The springs rarely wear out.  The main purpose for the shocks though is to provide compression and rebound damping.  Without damping, the bike will pogo up and down in the back as there isn't anything to slow the rate of spring travel.  The best way to figure out if your shock has any damping left is to remove the springs and then extend and compress the shocks by hand.  If they extend and compress easily, then the damping is shot.  If they are hard to pull and push, but still travel smoothly then the damping is still fine.  It's difficult, if not impossible to judge damping with the springs in place.  Those Partsnmore.com shocks are good shocks.  They are a bit on the stiff side, but I use them on vintage race bikes and they stop all wallowing in the back of the bike.

Tracy

Offline MCRider

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Re: Best test for rear shocks?
« Reply #6 on: June 13, 2009, 12:22:13 PM »

Shocks only do two things.  Firstly they hold the springs in place.  The springs rarely wear out.  The main purpose for the shocks though is to provide compression and rebound damping.  Without damping, the bike will pogo up and down in the back as there isn't anything to slow the rate of spring travel.  The best way to figure out if your shock has any damping left is to remove the springs and then extend and compress the shocks by hand.  If they extend and compress easily, then the damping is shot.  If they are hard to pull and push, but still travel smoothly then the damping is still fine.  It's difficult, if not impossible to judge damping with the springs in place.  Those Partsnmore.com shocks are good shocks.  They are a bit on the stiff side, but I use them on vintage race bikes and they stop all wallowing in the back of the bike.

Tracy

I'd agree with that.

To follow up on Hush's original post, if bottoming out is the problem, that's a spring problem not so much a shock problem. The shock will slow down the rate of spring compression, but it won't stop it from bottoming out.

And many of the older shocks did most of their dampening on the rebound, relying primarily on the spring to control compression.

I mean, the best shock will still bottom out if the spring is too weak. Either you are too heavy,  ;D, or the spring is sacked. Do what Triffecpa says, remove the spring then test for damping firmness and you can feel if the oil is gurgling past its valves meaning the oil is done for.

Of course you can just buy the new shocks and you're probably safe. Are we talking about replacing the original shock that came with the bike? If so, you can bet its sacked. The concensus is factory shocks on all but the recent 15 years of sportbikes or higher end streetbikes, are/were inferior on the showroom floor. So anything new is probably a step up.

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Offline strangedaze39

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Re: Best test for rear shocks?
« Reply #7 on: June 13, 2009, 12:38:03 PM »
I ended up replacing my shocks when I realized how soft my springs were, if I went over a crack in the road the bike would want to bounce. They were just very touchy. After replacing the shocks, the ride is more rigid but it's much better then riding a pogo stick.

BTW: The shocks I got from cyclerecycle for $100.
« Last Edit: June 13, 2009, 01:38:37 PM by strangedaze39 »
1972 Honda CB350F

Offline MCRider

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Re: Best test for rear shocks?
« Reply #8 on: June 13, 2009, 01:25:09 PM »
I ended up replacing my shocks when I realized how soft my springs were, if I went over a crack in the road the bike would want to bounce. They were just very touchy. After replacing the shocks, the ride is more rigid but it's much better then riding a pogo stick.
Shocks are important for comfort and safety.

Forgive me if I seem overly whatever here. Just want to tie the symptom to the problem. While your springs were likely soft, that's not what causes them to bounce. That would be a lack of rebound dampening in the shock itself.

Weak springs = bottoming.
Weak shocks = bounce or pogo

It just helps to know what causes what, I think.   :)
« Last Edit: June 13, 2009, 01:26:41 PM by MCRider »
Ride Safe:
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1988 NT650 HawkGT;  1978 CB400 Hawk;  1975 CB750F -Free Bird; 1968 CB77 Super Hawk -Ticker;  Phaedrus 1972 CB750K2- Build Thread
"Sometimes the light's all shining on me, other times I can barely see, lately it appears to me, what a long, strange trip its been."

Offline WFO

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Re: Best test for rear shocks?
« Reply #9 on: June 13, 2009, 01:45:00 PM »
Have you tried adjusting the preload?
82 cb650 sc nighthawk - 78 kz 650 b

Offline manjisann

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Re: Best test for rear shocks?
« Reply #10 on: June 13, 2009, 03:15:17 PM »
Quote
Either you are too heavy,  ;D , or the spring is sacked.

Hey Hush, check your saddle bags for stow away sheep  :D

Brandon
Sure it's for sale! How much you ask?? Well, how much are you willing to pay??? Now triple it, that's the price!

1973 CB500 K2 - Sold the bike and bought a Mig, Miss the bike, Love the Mig :D
1980 CB650 Custom
1971 CB500 Frame 650 engine: Project

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Offline WFO

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Re: Best test for rear shocks?
« Reply #11 on: June 13, 2009, 03:29:38 PM »
Ya know with my 82 nighthawk i ride 2 up alot (original shocks) with i take my son to school and he weighs 130ish so combined between the two of us 284 lbs and never bottomed out, buuuuuuut i did adjust the preload.
82 cb650 sc nighthawk - 78 kz 650 b

Offline Hush

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Re: Best test for rear shocks?
« Reply #12 on: June 13, 2009, 03:30:40 PM »
hey my panniers are full of tools!
You never know with these old bikes when you are going to need half your shed on the side of the road. :D
To answer McRIDER I would say these are definately the original 30 year old shocks as the tops are white (painted to match the Police bike) and the inner shocks are red.
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline Hush

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Re: Best test for rear shocks?
« Reply #13 on: June 13, 2009, 03:38:53 PM »
OK done some calcs and from Dave Silver in English Pounds 65=$165 NZ dollars
                                                  Partsnmore in US dollars $75=$116 NZ dollars.
I'm betting the cost of shipping would not be the $50 difference. :)
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline WFO

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Re: Best test for rear shocks?
« Reply #14 on: June 13, 2009, 03:58:18 PM »
OK done some calcs and from Dave Silver in English Pounds 65=$165 NZ dollars
                                                  Partsnmore in US dollars $75=$116 NZ dollars.
I'm betting the cost of shipping would not be the $50 difference. :)


I have done business with partsnmore and was completely happy with the price and the service.
82 cb650 sc nighthawk - 78 kz 650 b

Offline OldSchool_IsCool

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Re: Best test for rear shocks?
« Reply #15 on: June 13, 2009, 04:36:43 PM »
Quote
Either you are too heavy,  ;D , or the spring is sacked.

Hey Hush, check your saddle bags for stow away sheep  :D

Brandon

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Offline Hush

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Re: Best test for rear shocks?
« Reply #16 on: June 13, 2009, 05:20:23 PM »
Just removed the pannier bags, all sheep removed.... :D to get at the shocks.
Took the left side one off but even then it doesn't tell me much so will drop into the local Honda dealers tomorrow and get them to check it, will also ha ha ha ask how much a replacement set is. ;D
I really like the look of my old shocks with the matching white covers, can the new black covers be removed and my old ones put in their place?
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!

Offline Pinhead

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Re: Best test for rear shocks?
« Reply #17 on: June 13, 2009, 10:13:32 PM »
Hmm...

https://www.partsnmore.com/cat_index.php?model=cb650_sohc&category=chassis
Quote
Fit: CB650 (80-82), CB650C (80-81) Custom, CB650SC (1982) Nighthawk.
High Quality Replacements.
14 3/8" (365mm) Eye-to-Clevis mounting.
NOTE: These shocks are eye and clevis style mounting, NOT the eye and eye style mounting shown in photo.

Wonder why the '79 isn't listed. Are they different??
Doug

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Offline ludo410

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Re: Best test for rear shocks?
« Reply #18 on: June 13, 2009, 10:46:16 PM »
hey at least you guys have shocks my cb750 had aluminum plates bolted to them.. guess the guy wasn't happy with the ride height

Offline Hush

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Re: Best test for rear shocks?
« Reply #19 on: June 13, 2009, 11:42:50 PM »
I just emailed them asking why no 79 model listed.
I think the thing I most like about motorcycling is the speed at which my brain must process information at to avoid the numb skulls who are eating pies, playing the ukulele, applying make-up etc in the comfort of their airconditioned armchairs as they make random attempts to kill me!!!!!!!