​ I have been running the Sirio X5 and XRd ss5 for this past half year with empressive results. Other racers can't believe it. When i tell them whats in my mp10tki2! Now i won't stop using them.

the reason i started was because i upgraded from a Reds wr7 to a gen2 721. WELL! with not even a half gallon after break in the motor started giving me Serious issues. Like bearing/rod failure. I didn't want to be down waiting on parts so i found the X5 for less than 300 dollars shipped. Got it, broke it in, and away we go!

During this time I podiumed 3 times with the X5. Paired with reds quatro clutch, and Xone exhaust. 1 first place at the club 2 3rd place finishings in the nitro pro series. Wowing everyone a long the way. The little X5 has very smooth power, and in no way lacking at all!

The 721 was back in business at this piont, but i just left it in the pit box as a spare. Ended up selling my wr7 to a friend. Took that cash and bought the XRD ss5 ceramic(limited edition 2021 Sirio).

So now i am running the ss5 keeping the x5 as back up and letting the reds just soak in after run oil lol. These motors so far got me hooked. Smooth power, GREAT POWER, easy to tune. That is my experience with them. I did not tear down motor before or after break in neither. All i did is pull back plate off and check if bearings where truely Ceramic and the cranks are as claimed!

So i will be racing Siro/XRD for a while. Even stocked up on crank bearings. So far great motors.