I got my ninja last year it is the same thing as your grp here is what I posted about the break in.The medium plug I used is a number 6.

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Well I got my mr21ro1a fully broken in yesterday.She seemed completely broken in after the 12th tank.I had absolutely zero problems with break in.The one thing that shocked me with this engine was how fast it lost pinch.Like my picco .26maxx had about 2 times the pinch compared to my ninja and it lasted for about 16 tanks or more.I don't see how this break in could have weakened the rod but I will check it before I run it at the track.I ran a medium plug with 20% even though it was shimmed for 30% just because everyone was talking about the excesssive pinch.It was about 90 degrees outside with about 70% humidity.I will install a cold plug and run 25% for the rest of the engines life.I started tweaking the needles on the 11th tank and had it pretty good but still alittle fat on the top by the 12th.I don't think this engine is any harder to tune than other aftermarket motors but the tuning window is pretty small for that "sweet spot".Running it full blast like it would if it was at the track resulted in temps of 240 when the temperature outside was 80 because a storm blew over and cooled everything off.Maybe these guys are blowing there rods because they are more sensitive to lean conditions?


http://www.rctech.net/forum/exclusiv...ml#post4518679