Here is the problem with the 61mm drop in cylinder. I have been in this business many years and I will tell you with certainty that regardless how you drive, that drop in kit is trouble. The normal 61, mm that needs the case bored is thin to begin with but if built and set up correctly it will last as long as the stock. With the drop in kit the outer diameter is cut down so as to fit the case making it too thin for even the lightest driving. Your engine will run hotter adding to the problem. In perspective when you measure the 61mm drop in thickness it will be thinner than a 63mm where the case needs to be bored. Regardless of what anyone tells you the big bore kit will not make any more power since the stock cylinder only fills to about 55% adding a larger bore will not increase above 55%. The only way to increase power is to increase the volume in the cylinder and that is accomplished with the head and cam. You will be much better off investing in a good quality performance head and cam. Jetted properly you will have a seat of the pants difference.
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