While you wait for answers, we may have found some information which could help you.
Click here for Spring Grass Helpspare part for challenge extreme?
Blade guard?
How to fix Challenge Extreme Grass Trimmer 350W Product number SRT 350B?
Spring for Prop Shaft in a 250W Grass Trimmer?
what is the sparkplug gap setting?
Where can I buy a primer build for a challenge extreme lawnmower xss40a?