Grinding template to port cylinders??,

[Andy Birch]

Guys,

Does anyone have a tried and tested grinding template they could share with me to allow me to port my china 88 (66)cc cylinder at home please? Thanks, Andy

 

[sp1ke]

because of variations in machines sold that would be inpossible without knowing the donor of the templates has the exact same block from the same mfr then u got variations in what setup the engine has or what u want from it u might want a torquey hill climber or a speedy bike on the straight that suffers up hills variations in inlet tube from carb and exhaust flow bk presure so on so on so on

for these reasons i sugest learn what u need to know before you touch it u can allways take material away easyly its harder to add

base it on what u want from your machine dont over do it

or the genral bodge people use to advance all there ports at sacrifice of compression is to add a base gasket advancing when ports become open and blowdown duration amount of time they are open for

this adds that amount to the top of your chamber oposite effect of milling the head down decreasing compression instead of adding it aswell as increasing the volume of air in the crank slightly

wich drops compression at the head a lot so if u do that u would want to increase compression removing one of your head gaskets or milling it a lot of people do that

i prefer to port it properly wich means learning how to port where to so on

ive been porting a 66cc today funny enough polishing and port matching polishing and flowing my inlets and exhaust port engine side cant do exhaust outer matching till i make a new pipe

 

[Steve Best]

To learn anything about performance, you have to read the bible:
http://www.amrca.com/tech/tuners.pdf
Gordon Jennings wrote this book in 1974 and it is still 99% valid today.
Read the the theories and the principles.

The porting business is big, and templates are a booming market, but it is a bit crooked.
More is not always better.
For example a big HP motor may not be able to pull away from a stop or make it up a hill.

This pict is from another engine but gives an idea of how to mod the exhaust for more torque and power:

Widen it at the top of the port. Don't go much higher. Height loses torque.
If you have enough width, you don't need height.
Don't take anything off the bottom of the port or the sides at the bottom.
No gain down there and you will lose torque again.

Same on the intake side. Widen the sides only but at the bottom of the port.

Once this is done you can use basegaskets to experiment with raising the ports.

Do NOT port match the intake to cylinder.
A big mismatch (14mm intake to bigger cylinder port) works well here.

Steve