Help with Kymco 50cc 2 Stroke Scooter

[auswi]

Hello,

My wife has a 2007 50cc Kymco 50cc 2 Stroke Scooter Model Bug but I think it is also known as the Yup here in Adelaide Australia.  (7600kms on the clock)

The bike gets to 60kph initally but after about 5mins the bike only does 10-15kph with the throttle wide open.  I took the bike to get serviced and was advised the exhaust has a build up of carbon which is causing the engine to bog down although they did not take the exhaust off.  After talking to another mechanic he advised if that was the case it would bog down under accelleration all the time even when you start off with a cold engine.  Would running too rich cause this issue and if so how can I adjust this.

Any suggestions appriciated

Thanks auswi

[eamartin]

After about 5 minutes, when the bike only does 10-15kph, does it run steady or does it miss out; does it run slow for a bit then stutter, recover and run slow again for a bit?  Please describe it.

[auswi]

The scooter appears to run with the same engine noise as 60kph but just runs at 10-15kph but there is stuttering

I started her bike today and noticed it wont rev all the way with throttle wide open, sometime higher revs then other times, bike is on centre stand and there is alot of stutter.  I can see petrol flowing in the fuel filter.  sounds like a fuel starvation issue if I was to guess but that is only a guess

Cheers

auswi

[scooterfan]

Hello,

My wife has a 2007 50cc Kymco 50cc 2 Stroke Scooter Model Bug but I think it is also known as the Yup here in Adelaide Australia.  (7600kms on the clock)

The bike gets to 60kph initally but after about 5mins the bike only does 10-15kph with the throttle wide open.  I took the bike to get serviced and was advised the exhaust has a build up of carbon which is causing the engine to bog down although they did not take the exhaust off.  After talking to another mechanic he advised if that was the case it would bog down under accelleration all the time even when you start off with a cold engine.  Would running too rich cause this issue and if so how can I adjust this.

Any suggestions appriciated

Thanks auswi

I think you should take the first mechanic’s advice serious and get rid of all carbon in the exhaust as a starting point - otherwise you might be running in circles for the rest of the year.

[eamartin]

Did the bike run well for you previously?  Did this condition arise suddenly or incrementally?  Have you made any modifications to the bike?

[auswi]

The Bike was running well prior to this and the onset of this issue was incrimental over a few days

[eamartin]

To test for clogged exhaust, I have removed the exhaust pipe/muffler and then ridden 2 strokes to see if the removal cures the problem.  I doubt you'll want to do this.  As for the fuel delivery restriction, possibilities include restricted air hole in gas cap, clogging of fuel filter, improperly functioning fuel valve diaphragm and intermittent blockage of internal carb passages.  Gas cap problem can be tested by loosening or removing it for a test ride.  Fuel filter can be replaced or temporarily eliminated.   The fuel valve diaphragm could be bypassed if it is a separate unit (carb vacuum port would need to be capped off to do this.)  If the fuel valve diaphragm is part of the tap threaded into the bottom of the fuel tank, this would be problematic.  One could somehow just rig up a temporary fuel tank delivering fuel directly to the carb (no diaphragm, no vacuum line, no filter).  One thought just came to mind...a deteriorating vacuum line from the fuel valve to the carb (or carb manifold).  This would be cheap to replace.  Or, see if it's hard/brittle at its' tip, cut off an inch and re-connect.  Correcting blocked carb passages is self-explanatory.