​ 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.

old thread But was wondering the X5 what style pipe, low to mid/ or mid to high style

For those who run the Boss .28, the needles in the carb are the needles used in the MR Ninja/ Grp .21. If you can source the Ninja/Falcon/GRP .28 needles, massive improvement in not only tuning but Power!!! I have all the 28 mentioned and the Boss is wayyy tame vs the others ., until you put the proper needles in it. Tonight I was putting a tune on it and noticed the lsn sticking out wayyy farther than my Falcon that I was running last weekend, then I checked my Ninja and GRP 28s and they were all about flush, had me scratching my head . Then I grabbed my GRP .21 and the lsn was sticking out like the Boss 28 so I checked the GRP 28 needle and Ninja 28 and its vastly different when compared to the Boss. Then I compared the Boss 28 to the GRP .21 lsn....identical. Swapped the GRP 21 hsn and lsn and Boom show time! I guess this is another way they made sure the others were superior to the others as far as performace..? Maybe these were assembled when the "correct" needles were no longer availible ..?The Boss crank pin is the same as the Ninja 28 BTW. I'll time the crank soon and compare to the Ninjas as well as the sleeve but from eyeballing the heights of the ports its Identical. Long story short, swap the needles and it feels and sounds like the Ninja/Falcon. My Grp is a tick tamer than the others. Cheers Guys!!

Thanks for the information.