Modern Vespa

Hello guys,i have a vespa lx50- 4 stroke,4000 km from new,2012 year until now no was problems,but one week ago start problem,when was cold, time to time when start engine every morning hard and hard..one morning was imposible to start...change,new spark plug,clean and check carburetor,vaccum hose and fuel line are new, air filters new,valve clearence are ok,fuel pump works...maybe you have some ideas to help me !!!please share your oppinion or experiance,thanks

take the sparkplug out, still connected to the wire, put base of plug on bare metal part of the engine, then try to start. See if there is spark. If not then you have a problem with the coil (the wire), the plug cap, or the CDI

maybe the CDI. I had to replace my CDI on my 2008 LX50, it's a very common problem.

Or maybe you have a problem with the kill switch. When you say the engine doesn't start, do you mean that the engine doesn't crank, or it cranks but doesn't fire? If no crank, then the kill switch might be the problem.

I checked ,spark is,engine crank but not start,sometimes starts but after few second off.or stars and want to drive,and engine off or sometimes sart try to excelerate but engino doesnt want to excelerate..

you could also have a leaky carb or a leaky intake manifold

From wich place can be leaky carb and intake manifold??i saw and didnt see some cracks or something

While cranking the starter, spray brake cleaner or carb cleaner all over the intake manifold. If no impact on engine, then likely no leak.

A carb leak would be inside the carb, likely something with the diaphragm not seating properly. You would have to disassemble the carb, clean all of it well, put some grease on the diaphragm seat, and then reassemble. While you are at it, check for plugged jets.

Another try to try is to spray starting fluid or carb cleaner into the airbox while cranking the engine. See if it fires. If yes, then you don't have spark problem, you have a carb problem.