Hi Ragz, I don´t have the 40 but i have the 50 and the 80RV. In the RCShowcase site it says that the distance between the magnet and the sensor for your engine should be 5mm. That could become a majop problem for starting your engine or make it run properly.
This is the link, scroll down a bit and you´ll find it.
http://www.rcshowcase.com/html/faq.html

Hope this helps
John