Engine-valves usually get tighter as they're used.

The symptoms of engine-valves that are too tight, are as follows:

* Bad fuel economy
* Difficult to start
* Stalling idle

The manual for my scooter states that the engine-valves should be checked/adjusted every 4000 kilometers.

I've got 1 cylinder with two valves on my GY6 engine.

My question:

**Is it really neccesary to slavishly check the clearance on my engine-valves at the stated interval? Can't I just check/adjust if one or more of the three listed problems happen?**

With only two valves I imagine problems will be much more noticeable compared to an engine with more valves.

The answers so far has been focusing on adjusting the valves - I am questioning the checking/verification of the valve-clearance.