Originally Posted by PowerHouse

As far as the crank is concerned, the machining imperfections won't really hurt you. They are not impeading or changing the direction of airflow enough to matter. You can clean it up if you want without fear of screwing anything up. Its relatively simple. What is a big factor is the crank intake timing. The real gains in performance lie within the duration of the crank intake port and what degree it opens and close in relation to the transfer ports. You can clean up the edges if you want and again it shouldn't affect the stock degree specs thus not altering the engines stock running characteristics. The one guy is exactly right about the polishing aspect. Alot of people firmly believe that a polished surface is smoother and more efficient but after years of racing snowmobiles and personal watercraft and designing engines for factory polaris's race program, we have found that a course surface maintains a suspended molecule structure which in turn keeps the velocity speeds up and keeps the molecules from dragging along the surface which ends up as fuel puddling on the intake side and carbon build up on the exhaust side. As far as the "tear drops" in the windows of the ports, alot of engine manufactures are putting them in on their transfer ports. The theory is to help guide the mixture into the chamber but whats more important than just getting the mixture into the chamber is at what angle and speed it enters. Two stroke engines are loop scavengers which means the fuel/air mixture should enter angled up and away from the exhaust port towards the rear booster but not to interfer with the rear booster entry. The mixture then travels up the back wall into the dome, fires, rolls over and exits the chamber through the exhaust port completing the circuit. A common misconception is that a 2 stroke engine fills the entire chamber. The idea is to keep the new mixture entering the chamber away from the exhaust port because the exhaust opens first and closes after the intake portion of the cycle. If the ports push fuel towards the exhaust port, some of the new charge gets pulled out of the chamber during blowdown causing the motor to lean out. A common remedy is to open the needles to compensate for the lost fuel resulting in reduced fuel milage and loss of engine effciency and the fuel that gets wasted also burns in the pipe increasing engine temp due to the pipe pushing the hot gases back into the exhaust port when the pulse returns and that also starts a vicious preignition cycle that causes detonation and can ruin your engine if not found soon enough. There are alot more factors that makes these engines perform the way they should and there are alot of different opinions you will hear as you go along. There are alot of good engine guys out there and its good advice to listen to them and see if you can pick up any similarities between them. If you guys are interested in some engine work, you can visit my website at www.PowerHouseRCPerformance.com I also have a more detailed explanaton of 2 stroke operation if interested. Good Luck gentlemen and i hope to hear from some of you soon.

Mark @ PowerHouse RC Performance