Kevins Question  : Hello, I contacted you for a little information , I'd recently changed piston / rings and seals valve stem ( by a pro ) when starting my engine , white smoke comes out, and a smoke also when stop , do you know would it come? thank you

UPower : white smoke is water , a blue smoke is oil

There is no water in these engines but there may be condensation into the exhaust is returned to the silencer during washing .
So white smoke at start and which disappears when the engine is hot it does not matter

A light blue smoke disappears hot is normal. All engines consume oil and burned by the smoke .
Thick smoke including hot deceleration is a sign that the engine does eat oil
Must be checked by monitoring the engine oil level. If greater than 1/4 liters afternoon consumption ( about 3 or 4 hours ride ) it is useful to disassemble the engine.
The mean wear come from the rings due to the dust that enters into the engine from the foam air filter . The cylinder sleeve is no many wear.
The valve stem seals do not wear out too. Should be at least 10 years or 50 000km to justify their replacement

Take care in case of mistake, if new rings are for a 52.4 bore and you put them in a cylinder 56mm , even new, it will smoke !