Sahartman, I've had a plastic retainer on the new TT bearings fail and destroy a piston. A set of stainless front and rear bearings can be had from RC Bearings for around $12.00 including shipping. I just ordered two sets, and the prices went down! Go figure? Speaking of the newer generation engines versus the older generation. A lot of us feel the the older engines out perform the newer ones, so always keep an eye out at swap meets for used TT Pro 40's. Don't search so much for the older carburetor (straight needle valve), but look at the cooling fins on the crankcase. The fins on the older engines are not machined. The fins on the newer engines are machined. Often the color of the older engines is gray, compared to a brighter silver on the new engines. This is only speculation, but we believe the changes came about when they stopped production in Taiwan, and moved it to mainland China. Quality may have also suffered? Good luck, Greg