My first 4 stroke engine. Replaced a Super Tigre .75 in a Hangar 9 Spitfire MKII 60. Throttle arm on the same side so basically a drop in. Startled me by starting on the first flip. Starts and runs as good or better than any engine I have had in 50 years of model activity. Liked it so well I purchsed a Magnum RFS .52 for my Kaos .40. Same experience as the RFS .91. Usually one flip starts and flawless performance. Thank you Hobby People for great products at great prices.