After searching from various sources on the internet, finally I have found a custom rom Android 4.1 for Lenovo A800. I found it in the Chinese forum. If you are interested you can visit it here.
Here is the ROM information
Model name : Lenovo a800
Andrid version : 4.1
ROM Author : Supernova
ROM version number : a800ydss-Caoxinxin-lawa + MIUI
ROM Features: Based on official S126 original package produced extremely streamlined, ultra-small memory occupied
Step 1: brush into mobile uncle Chinese recovery. Tutorial also posted here
Step 2: Download this card brush ROM copied to the external SD card root directory
Step 3: shutdown state, data cable, one end of the phone, one end of the port of the computer. While holding down:
Power button + volume + volume keys (3 keys with the press) to enter the recovery Brush mode, first rec clear the user data and cache, and then enter the card brush
Options Brush can.
Step 4: Brush complete, restart the phone
I can not install this ROM, after download the package error for me