The STS carburettor is made of composite plastic. It will not have overheat problem. Besides, STS's spray bar(mid-needle) has 4 holes on it. Racers can lean it to get extra-power and fuel supply still will not cut off. So it don't have adjusting limit.

Check those broken crankpin,first you will find that it's sign of overheated. Because the pin area is darker and also sign of too lean. That means the lubrication is not enough. And if you measure crankpin you will find it is not round any more. It's oval. The stock crankpin is 4.29mm diameter,just measure the top-bottom and left-right places. When the crankpin has very big play,the conrod will hit the crankcase and pull apart the crankpin.

There is a case I just deal with.Yeah~ Fisher's D3 broken crankpin too. From I studied his crankpin,it is 3.94mm diameter from top to bottom and 4.08mm diameter left to right.(New one is 4.29mm diameter)So 4.29-3.94=0.35mm . That is not only a little play.