Hi all, I'm new to the forum so please be gentle :D
I bought my 08 GS500F in Oct 2016 as my first bike..... I'm loving it so far, gives me everything I need for my first bike.
I was due a MOT today and the guy at the garage failed it as the rear shock needs replaced, the bike's only done 15k miles though and I know the rear shocks on the GSs are notoriously soft, is there any way I can tell the rear shock's gone before I need to fork out for a replacement
Thanks in advance, Mark
A blown shock would likely be wet with oil. Or, it would spring back up with a hard clunk after being compressed.
Thanks pliskin,. No oil and clunk......just a bouncy rear end
Yes.......it failed the MOT!
Do you know better than the tester, someone who spends every working day examining shocks and various other motorcycles and their component parts?
If something has failed internally the shock will go soft without leaking any oil
Even if you take the bike elsewhere for an MOT the failure is recorded against the reg no and they will be all over it like a rash.
If you are on a budget buy a used replacement, clean it thoroughly so it stands out, fit it then take the bike back for a retest. If they can see you have made an effort they are more likely to give you a pass.
I know it failed sledge, I'm not arguing the point. It's my first bike, so far I've managed to do some maintenance myself and I've learned a lot about the bike in the few months I've had it but I'm not sure how "I" can tell the shock has gone. As I said, I know the rear shock is notoriously soft, having never ridden anything else before I have nothing compare to, which is why I asked the question.
When the back end is pushed down how much "bounce" should there be......is there a measurement that's used or is it a best guess that's used?
Pliskin's already said that there should be some oil and a clunk, which there isn't any of either, which is why I'm looking for clarity
Cheers
No oil outside the shock = its not blown a seal.
Of course a GS shock is dead when it leaves the factory.
Usually they don't clunk. The shock will pogo but it would need to have a spring stiff enough to pogo. Else it wont. I think a GS shock is pretty soft and likely wont anyway.
I blew a GSXR shock once and that did pogo discernibly.
Cool.
Buddha.
Well the only real way to tell is to put it on a shock dyno.
Hey first just a touch of theory/terminology here. The "shock" on the rear of your GS500 is comprised of a coil spring that is integrated with the damper ("shock absorber") in a coil-over fashion. Presumably the thing the inspector says is "gone" is the damper portion, not the spring.
The job of the damper is to prevent oscillations of the suspension. When it is compressed, it will rebound and the weight of the motorcycle on the spring is like a giant pendulum that will cause the thing to go up, down, up, down for a long time (oscillate). The damper is there to prevent it from cycling through this oscillation, so if you compress it, it will rebound back to something like the original position and stay there.
If you pulled it all the way off the bike and remove the spring (which is not trivial), then you could "hand check" the shock to be sure there is at least SOME damping but you will never be able to apply the forces and rates of force that it gets on the road this way.
The normal test is if it bounces up and down when you compress and release it, then the shock is shot. If it rebounds and comes to rest on its own without oscillating, the damper is at least doing SOMETHING.
It's the spring rate that's "notoriously soft", not really the damper. The damper is matched to the spring from the factory. A heavier spring will exert more force on rebound so it requires more damping to control it. A soft spring doesn't require as much damping.
I think if the shock were truly shot, you'd know it by riding it. The rear end would be obviously very uncontrolled and traction would be a serious problem. If you went over any kind of bump especially in a turn you'd be in for quite a thrill ride. I don't know for sure because I've never experienced it, but I can assume.
My suspicion is the inspector saw oil on the shaft of the shock and assumed it meant it as defective.
No........there doesn't HAVE to be an external leak or a clunk for a shocker to be faulty. There are internal seals that can fail.
What does the report say? Oil leak or inadequate action? They are two different failures.
I suggest you ask the tester, its all at his discretion :dunno_black:
Give us the reg of your bike, I can check the failure result on line and comment from that
The MOT fail reads "rear shock absorber has inadequate damping effect"
If it was leaking the failure would read something like " evidence of leakage from shock absorber"
The tester has used his judgement and discretion to decide the shock has failed or is worn, he doesn't have to be specific but if it was visibly leaking it would say so in the documentation.
Its 9 years old, they don't last forever :dunno_black:
Take look at this.....
http://www.motuk.com/bike/2-4.asp#Menu_Top
Thanks sledge. I guess the experience the tester has gives his the knowledge of what's good vs bad. Looking at the link and the MOT fail reason (2.4.A.3b ) it coincides with inadequate damping effect.
I might go for a straight swap from a gsx600f........ is it a case of get the bike on the centre stand, undo the 2 bolts on the shock and replace..... or does the rear wheel need to come off?
That's a "Katana" over there right? If so you don't have to remove the wheel at all. You do have to remove the seat, tank and air box. The shock comes in and out through the opening where the air box sits. It won't fit going through the bottom. But besides that, yeah it's remove two bolts and Bob is your uncle.
Mr72, yeah, it's a Katana in the UK. I've already had the seat, tank and air box off before so shouldn't be too difficult to do a swap for the shock by the sounds of it.
Thanks for everyone's help
Quote from: sledge on May 25, 2017, 12:59:32 PM
No........there doesn't HAVE to be an external leak or a clunk for a shocker to be faulty. There are internal seals that can fail.
What does the report say? Oil leak or inadequate action? They are two different failures.
I suggest you ask the tester, its all at his discretion :dunno_black:
No the way a GS shock is built, this can not happen. Fluid is passed through metal orifices in he damping rod and big plungers with holes etc, there is no sealing in it from chamber to chamber. The shock has to lose most of its oil for this to fail.
Think of it ad moving your hand through a trough of water. In fact a trough of water will make a batter shock than the original GS one, but you get the idea. the trough has to be lower in water level to get the "damping" action to stop.
Cool.
Buddha.
Quote from: MD77 on May 25, 2017, 01:20:53 PM
The MOT fail reads "rear shock absorber has inadequate damping effect"
OK the new shock is that way, now how was yours bad then ???
Cool.
Buddha.
If its your first bike you may not realize how bad the shock actually is. You have nothing to compare it to. I bought my GS500 with 14,000 miles and didn't realize for a few months that the bike already had a blown shock. I think it was blown when I bought it.
If you try to ride the bike hard in the twisties you will realize how dangerous it actually is. Turned out I wasn't dragging my center stand because I was a really good rider. It was because of the shock.
If you ride the motorcycle at highway speeds on a concrete road (not asphalt) with expansion joints you may pick up an oscillation in the rear end from the small bump at each expansion joint. When my shock was really blown my bike would pogo stick down the highway. That was when I knew I had to get a new shock. I replaced it with a Katana (GSXF600) shock. If you weigh under 190 lbs (86 kg) the Katana shock will be too stiff for you. Get an R6 shock instead.
If you replace the rear shock with something stiffer make sure you get new springs and oil in the forks as well. A soft front end with a stiff back end is a bad idea.
I'd vote for the R6 shock as well. Perhaps the best mod I've done on my bike. It's great having the adjustable compression and rebound damping, which the stock shock does not have.
Replacing shocks is not exactly a plug and play. It does take some fiddling to get the bike lifted properly, and a bit of pounding to persuade all the linkage holes to line up.
There's a lot of threads on shock upgrades on this forum. Also some more info and pics on my build thread in my signature below.
The bike definitely does bounce a bit, but you'reright, I've nothing to compare it to.
I'm only 70kg so sounds like the R6 would be best. Had a look at a vid on YouTube, looks like the guy needed to do some grinding.......I know it might be a tight squeeze but does the R6 need that type of work to fit
The airbox is going to get in the way of a piggy back reservoir shock, but not a remote reservoir shock.
That may be a consideration for a MOT - cos without an airbox would you clear that ???
Cool.
Buddha.
Quote from: The Buddha on May 25, 2017, 03:07:32 PM
Quote from: sledge on May 25, 2017, 12:59:32 PM
No........there doesn't HAVE to be an external leak or a clunk for a shocker to be faulty. There are internal seals that can fail.
What does the report say? Oil leak or inadequate action? They are two different failures.
I suggest you ask the tester, its all at his discretion :dunno_black:
No the way a GS shock is built, this can not happen. Fluid is passed through metal orifices in he damping rod and big plungers with holes etc, there is no sealing in it from chamber to chamber.
Yes.....and there is a seal on the end of the damping rod were it contacts and slides against the inside of the body..... think piston, cylinder and rings. This seal will have failed and will be allowing the fluid to take an alternative and easier route when under compression by bypassing the restrictive orifices. This in turn reduces its effectiveness and because the seal is internal there will be no fluid loss.
There is a seal on the
Sledge - no seal. Not even on a GSXR non remote reservoir shock, which I have one cut open. It has 2 seals on the top side, one on the rod (rod viper seal) and one around the edge but that shock is 1000 times better built, it has adjustable orifices etc etc but no seal internally. There is no need.
Think about it. Its not compressing fluid really. If there is a pressure differential the piston moves till that differential is gone. The resistance to that movement causes the piston to not overshoot and pogo. Simple when designed and implemented properly.
Even a front fork does not have seals except to keep the fluid in. They are not required. There is a metal ring on the damping rod which does a pretty fair job of forcing fluid down the thing instead of around it. Maybe you're calling that a seal ??? There is no other rubber part - how about that.
Your hand moving through a trough of water creates the required resistance - only seal needed there is to keep the water from getting out of the trough.
I will try to pull the cut open shock I have and get a picture.
Remote reservoir, piggy backs, gas charged etc etc shocks need to keep the nitrogen etc etc - whatever - I have not cut these open. The shocks I have sliced - katana, GSXR pre remote reservoir, and GS. These 3 are all no piston seal. Their seals are right at the top where the rod has a rod viper seal, and the edge has a O ring keeping the fluid in.
Cool.
Buddha.
Yes, you'll likely have to grind out a bit of the front of the swingarm as the R6 shock spring has some pretty thick coils. I have some pics in my thread about the area you'll need to work on.
I'm close to your weight, and the R6 shock is awesome.
Quote from: Endopotential on May 26, 2017, 11:30:12 AM
Yes, you'll likely have to grind out a bit of the front of the swingarm as the R6 shock spring has some pretty thick coils. I have some pics in my thread about the area you'll need to work on.
I'm close to your weight, and the R6 shock is awesome.
Of course. Or really just replace the shock with another GS500 shock that's not in bad shape. Which will drop right in with no grinding or modification. And costs 1/3 what an R6 shock will and 1/2 what a GSF600 shock will. They are a dime a dozen. And they are not THAT bad.
mr72 has a good point.
You are light enough that the stock GS500 shock should be just fine. You could get a used one from a more recent bike with low miles for cheap.
O/P?
Your bike failed its MOT on a duff shock.
This fact is now recorded and every MOT station in the UK will know this when they enter your reg into the system
Consequently the station you use for the next test will be paying special attention to the shock and ensuring its satisfactory and serviceable.
Do you really think they will pass something that's had lumps ground out of the metalwork surrounding it.
Do yourself a favour, put a standard shock in. These mods work fine for the Americans because there laws are different than ours, they don't always work for us.........and another thing, check your insurance policy. If you have made serious mods to your bike without telling them they will laugh in your face if you need to make a claim and leave you up shaZam! street.
Not going with the R6, too much hassle. The GSX600F shock seems as if it'll be a bad ride due to my weight so bought as stock shock of a GS500E....... I'm hoping it'll be decent when it arrives.
Am I still looking at removing the air box etc for a like for like shock
Cheers
Yes you have to pull the seat, tank and air box to get the shock in and out. Might as well get used to it. I've have had to do this so often I considered quick release fuel lines.
Quote from: mr72 on May 27, 2017, 04:55:01 AM
Yes you have to pull the seat, tank and air box to get the shock in and out. Might as well get used to it. I've have had to do this so often I considered quick release fuel lines.
No, park the bike on a 2X4 and you can drop the rear shock out the bottom unbolting the linkage.
Well the linkage bolt usually is so tight that you may be better off getting it out the top, unless you had an air/impact wrench.
Cool.
Buddha.
Got a shock delivered, like for like from a GS. Fuel tank off, air box off, f*ck off....can't get the top bolt loose.... into the shop it goes. At least the guy at the MOT station will see I've a new shock, silver lining n'all that