I had a gp-42 on the lt-40. I still own it but have replaced it with a os la .46 engine. that gp was tight!! it was so tight that when you started it would only get one puff out before it would allmost seize. I had to mount it to a test stand, oil every thing down with castor oil and get the duwalt 18 volt drill to turn it over. I had that thing spining untill it finally loosened up some. then we tried to start it up with the prop on and it took a few whole fuel tanks before it would start reliably. I dont think its that great of a motor but that is only one example.