MacAllister Pressure Washer Trigger Handle Tear Down and Can You Use Bosch Parts? 

The trigger on the MacAllister is very stiff so I wanted to open this up to perhaps remove a spring or at least reduce the tension. Check out what is inside this handle and how it works.
Also, this model actually uses Bosch parts for their new range of pressure washers. I've replaced the trigger handle and hose with Bosch parts and they work perfectly.
You should be able to replace your parts with Bosch parts from these models:
Easy Aquatak
Universal Aquatak
AQT
33-10
33-11
35-12
37-13
40-13
42-13