How to Port Engine Cases?! - A Tutorial On Porting Engine Cases



  • Hello guys, Daniel from Dan Racing here.

    Due to the lack of tutorials in this forum I decided to make a little series of them to help some new tuners into the scene.
    This specific tutorial on porting engine cases i'm using TDR125 cases(same as DT125RE/X) but theses things should apply to almost all of 2 stroke engine cases.

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    There are 3 main places to be carefull with, in all 3 of them, gasoline atomized into the air will flow through, being it's final destination, the cylinder.

    1 & 2 - This is one of the most important areas, because it's the part that connects with the transfer ducts on the cylinder, this connection should flow as much as possible. In here you should place the cylinder on the cases and check for any kind of 'step' between the cylinder and this part of the cases. if there is a step it should be eliminated to avoid any major disrupt in the airflow to the cylinder.
    If the cylinder is smaller than the cases, it's better to fill in the step in the cases with epoxy than cutting the cylinder, because the transfer ducts in the cylinder are made to mantain a straight area all the way to the actual port.

    3 - TEXTURE - Texture in the cases should be like stock, altough after porting them it's very hard to get the stock texture again unless you use some kind of soft sand blasting. The texture should be rough, but not too rough. I like to use the dremel grinding stones to do stripes(all really close together like in the first picture) 90 degrees with the airflow(Airflow in black, blue are an example of the stripes, the stripes shouldnt be deep at all, just enough to create small disruptions in the airflow to keep fuel atomized, this should create very small horse power gains, but you actually should gain more fuel efficiency due to improved atomization so smaller jets needed to achive a good A/F Ratio.

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    I'd love you guys opinion, or just tell me what you guys to for yourselves in terms of porting, im currently working on a guide on how do port cylinders so stay tuned to the tutorials category.

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  • @DanRacing Nice work. 👍🏻