Magento Frontend Catalog Search is incomplete

Hello Magento Expert,

We use Magento CE 1.8.1.0 and the standard Catalog Search of Magento with Like Search

The Problem is, our shop contains 2500 Artikles. Every Artikel ist setting to display at the Search Page and every Artikle is activated!
Magento Frontend Catalog Search is incomplete an contains only 518 Artikles.
For Example if we search for Artikle "Sunglass 22-6" so, "Sunglass 522-6" will display but the Artikle "Sunglass 22-6" is not indexed.
This is only one example of many!

What´s wrong? Does anyone have similar problems?

Is there an extension that replaced the Magento default search?
A SKU search alone would be fine!

Many Many Thanks!

By default SKU search is enabled. Any how can go to Catalog > Attributes > Manage Attributes. Select "SKU" from the attribute list and make sure "Use in Quick Search" and "Use in Advanced Search" is set to YES

Cheers
Arun