Author Topic: Sym Duke 125cc - front shock absorber rebuild  (Read 317 times)

gingel

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Sym Duke 125cc - front shock absorber rebuild
« on: May 30, 2021, 03:33:01 PM »
Hello,

I have an old scooter, SYM Duke classic 125cc.
One of the front shock absorbers is leaking from the oil seal.

I don't know how to open the shock absorber.
On videos i see on Youtube, you can see that the shock absorbers have like a cap which is a screw.
In my case there is no cap like that.
There is a black plastic/rubber cap which you can remove, and under it there is something else.
No screw to open.
See pictures:






Is it possible to rebuild this shock absorber?

Thank you.
 

Thoppa

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #1 on: May 30, 2021, 04:09:26 PM »
Hi,

Yes, it's possible to repair the front fork - at least it is on my SYM Citycom and I assume they have similar designs.

As you've found out, it's not quite the same design as a motorcyle - the top is sealed so it cannot be opened up that way. The whole top half of the fork is one unit and the lower half is another, and they are are held together by a hex bolt at the bottom of the lower leg. Turn the fork upside down and look down the centre hole to find the hex bolt. Once you've got that bolt out, the rest is more like a motorcycle fork.

You can replace the seals and oil but nothing else. If you can find out how much oil is in each leg that's best, but if not, try to collect all the oil that comes out and measure that. If you've got a leak, then of course, this is less than standard.

I use ATF fluid instead of motorcycle oil - it has all the same properties such as anti-foam agent etc but it usually costs much less.
« Last Edit: May 31, 2021, 05:37:53 PM by Thoppa »
Ninja 650R
Citycom 300

gingel

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #2 on: May 30, 2021, 06:21:53 PM »
Hi,

Thank you for the quick answer.
In the videos i watched on youtube, you can see they are also open that bottom hex bolt, but
they fill the oil from the top, where there supposed to be the cap that you unscrew.

I found this instructions from another scooter manual, and it looks like the same shock absorber design.

Seems like you need to push that top cap inside, and then remove a circlip to be able to take the cap out.
Problem is, it's not moving.  When you push it, it push the entire leg inside.
Maybe it so rusty it got stuck?



Thoppa

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #3 on: May 30, 2021, 07:58:32 PM »
Hi,

My SYM doesn't have a circlip inside the top of the leg - just a plastic cap sealed into the stanchion - which seems to be what you have too - no clear method of disassembly - and that's why I looked for another way to do it.

The upper half of the fork leg, the stanchion, has a circlip at the top on the outside - that's to ensure the fork leg mounts correctly into the steering clamp. But I couldn't find a circlip or anything inside the top. It seems they haven't followed other designs I'm familiar with.

Most cheap motorcycle forks use a bolt at the bottom to hold the damping tube/rod in place. It can be hard to remove - needs a shock torque, for example, from an impact driver. To separate the upper and lower parts of the fork (the lower leg from the upper stanchion), you have to aggressively pull the two apart with repeated force. But with the SYM, you just undo the bolt at the bottom and it freely disassembles. I actually found this disassembly easier to do than a motorcycle fork, and it's easier to change the seals. If I remember correctly, I removed the lower drain/assembly bolt with the fork upside down, using an impact driver. Then turned it right way up to drain the oil out of the hole where the bolt was. I seem to remember that the two halves are ready to fall apart so be careful when you turn it right way up - the two halves can slide apart just cos of their weight. After draining, slide the two halves apart, and remove the dust cap, circular retaining clip (check the clip isn't rusting - the rust can cause grit that damages the seal), then remove the old seal (and note the washer below it). Then I fitted new seals, reassembled, and then turned the fork upside down again to partly fill the fork with ATF through the hole where the lower drain/assembly bolt goes - do that slowly cos it won't flow fast through the hole. Then bolted it... and it's finished :-)

My SYM has an 8mm hex head on the drain/assembly bolt and I used 120ml of ATF in each leg. I also fitted gaitors after the change so the seals will stay cleaner for longer and I don't have to do that job again. And so far, about 18 months, so good. Here's my post about it: https://symforum.com/index.php?topic=12195.msg46460#msg46460

BTW, if it is a small leak, you may not need new seals - just cleaning the dirt out can be enough if the seal is in good condition. There are tools to do this such as:

https://item.taobao.com/item.htm?spm=a1z0k.7385961.0.0.464f43f17UNYdL&id=549961051963&_u=t2dmg8j26111
« Last Edit: May 30, 2021, 08:43:11 PM by Thoppa »
Ninja 650R
Citycom 300

gingel

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #4 on: May 31, 2021, 01:26:03 PM »
Thank you for the detailed explanation.  :)

With my shock absorber there isn't a plastic cap sealed into the stanchion.
There is that black cap which can easily be remove, and under there is what looks like
a metal cap but it's not a cap which unscrew.

Not sure we have the same exactly setup.
I don't want to open that bottom bolt until i'm 100% this is the right way with my shock absorber.

Why SYM don't use standard shock absorbers?

Thoppa

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #5 on: May 31, 2021, 05:35:53 PM »
Hi,

It's the lack of a mechanical drawings for the forks, in the service manuals or the parts fische, that I find annoying. I was just left to guess and try, and you are in the same situation. When I contacted the dealer, they didn't even know if seals were available - they wanted to sell me a complete fork "cushion". It's not that expensive but far more than just seals.

The only other issue I have with the 250/300 scooters is the lack of an oil pressure sensor.

However, the rest has been great and I'll likely buy another SYM to replace this one.
« Last Edit: May 31, 2021, 05:38:17 PM by Thoppa »
Ninja 650R
Citycom 300

gingel

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #6 on: June 17, 2021, 09:52:19 AM »
Hi,

You are right about the lack of a mechanical drawings for the forks.
There isn't even information about which type of oil to use, and how much
oil is needed.
The problem is my scooter is an old model, and the dealer doesn't even have
a new complete shock absorber.
So i either try to rebuild it somehow, or i can toss the entire scooter to the bin.

I think i'll try your method, to open it from the bottom bolt.

Thoppa

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Re: Sym Duke 125cc - front shock absorber rebuild
« Reply #7 on: June 19, 2021, 03:12:07 AM »
I hope it works!

Ninja 650R
Citycom 300

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