First gear problem - How to fix it ?

[Heryst78]

Hi guys,

I’ve got a problem with my GST.
It’s a 1997 engine manual.

The problem is when I want to drive, i take the first gear on but it jumps, and once of two it goes to neutral automaticly.
The others gears doesn’t jump, just the first.

Is there an adjustement to do at the clutch ?
Clutch is new, bearings too

Sorry for my english i’m from France

Thanks