Please can somone tell me whats wrong my Sym Symphony SR125?

Is my Scooter to rich or to lean?
Its fires up alright but theres hardly no power there..
I made a video so you can understand better


Thanks Ben.

 

first of welcome to the scooter shack ben.

now lets start, your scooter should idle at around 1,500rpm to around 1,900rpm. in your video the scooter is idling at way over 4,000rpm thats way to high.

if you have removed the carb at any point can you check its been seated again correctly the carb joining to engine needs to be air tight , usually its a rubber hose with a clamp, or a manifold like fitting with a little rubber O-ring seal, you must make sure these are intact, not split or damaged ( they cause airleak)

if you removed the airbox and put a open style airfilter, TAKE IT OFF, put your old airfilter back on and connect the carb to it ( your little scooter will run better with its stock airbox trust us on this ), make sure its seated correctly and connected to carb correct ( an airbox leak as with a carb manifold leak will cause scooter to run lean ) if you have an airleak you may find bike gaining higher rpm without touching throttle then dropping out to a stop as it becomes so lean it stalls itself..

First off, you need to address the idle rpm, check your throttle cable is not getting nipped or pinched holding the throttle slide up in carb.
check the carb throttle slide is fully seated down when there is not throttle added ( ie you twisting it). you should see a tiny little gap (remove airbox so you can see into the carb for this. with the airbox off have someone twist throttle open with bike NOT STARTED and check the throttle slide fully opens, if both the slide is closed without throttle and fully open when given full throttle its fine DO NOT MESS WITH IT. do not adjust the idle mixture screw at this point to just get the idle screw setting sorted first

your carb has two little screws on the side, one is for the idle setting and the other for the fuel mix at idle.
the tube where the throttle cable goes into carb is the slide throat and outside of that tube is a little screw ( idle screw) start bike and use a screwdriver to turn it anticlockwise and lower the slide , as you do this the engine rpm should start to drop, if the engine rpm starts to increase turn the screw the other way. use your tachometer and get the scooter to idle at around 1,500 - 1,900 rpm WITHOUT THROTTLE.

now see if the scooter starts to behave a little more, if not pop back

 

Hi Tamiyacowboy.

Last week while i was riding it, It just suddenly started to lose speed/power. Then it just cut out. After it turned over alright but just wouldn't kick in. Today it did kick in so I took i took it for a spin around the block. When I was riding i noticed that it wasn't enough power to go uphill. It was a doing around 15mph!.

The scooter has already got the stock airbox.

The Carb is seated tightly, there's no leaks and no splits, the Throttle cable is fine and i got some freeplay and turns alright.
Maybe the Idle Screw need Loosing or tightening? Also the idle mix screw needs tightening?

Theres nothing i can do now until the morning because its dark.
Hope you reply,
Thanks for your help
Ben



I have a SYM SYMPHONY SR125.
Heres a video i pinched of youtube of the scooter.

 

It does sound like it is revving hard but, I've just bought the same rev counter ... 1. What do you think to it; I've yet to put mine on and 2. Is it set up correctly, there are 2 settings according to my instructions 01 counts that the plug fires twice per revolution and 02 counts once per revolution.
Just a thought, which one do I use, I'm guessing 02 ??

Sent from my GT-I9195 using Tapatalk

 

if it was running and has lost power, i would advise on a compression test and maybe a leakdown test. possible the piston rings have started to fail hence the not going to well and lack of power. a leakdown test would show if the crank seals are leaking or not to.

i would try get a compression test done see if the rings have failed, that would be a good start, if theres compression a leakdown to check the engine seals and gaskest are in order and working good.

 

Check valve clearance, a tight tappet can cause low compression due to the valve being open slightly.

 

Yeah valve clearances and mixture screw need setting