VESPA ET4 50 Workshop Manual page 119

ET4 50
Engine
loss of engine blows as the mixture is too lean (low CO), ignition failure or, incorrect timing or a clogged
or unsealed exhaust valve.
If it is difficult to adjust CO values, check accurately:
- That the automatic starter is efficient.
- That the tapered pin-housing is efficient
- Tank level adjustments
ENG - 119