Hi Mr Lizzy
I have a Crrcpro 45, my mate has the 50 and we use the "so called crappy Jen Feng chinese plug" and they run like a swiss watch.
Run the plug gap at about .6mm (22thou) and it will run fine.
My suggestion is to run the engine before changing anything, the engines work fine and are very good value.

We have a lot of Crrc pro 45's and 50's at our club using the original plug.

Unfortunately there is a lot of "chinaphobia" out there.

Hope this helps
Cheers
Paul