cutting piston for reed valve (power porting)

[tavspeed]

hi all,does any one have any pictures or info showing the cut out in the piston to suit a reed valve,power porting,ithink it is called,i believe it starts near the inlet side gudgeon pin and slopes down to the piston skirt,dont want to put holes in,the piston unless i have to.
also what is the maximum i can take off the piston skirt on the inlet side without causing issues.cheers.

[Darrell Taylor]

you can either copy a ts1 type piston by cutting out a paper rubbing as a template although the cut out and windows are slightly offset when used on the piston port inlet or as you say without windows best place to start is marking out the inlet onto the piston skirt when its fitted up which will provide your 2 outer lines the top line of the cut again mark out the inlet onto the piston in pencil but do it in aound 4 positions at 2mm intervals starting from bottom edge of gudgeon pin down,then remove the piston and use your judgement as to what height you consider safe based on intended use/piston quality and skirt width/inlet port width
a wide inlet will mean your left with thin legs on the skirt so you wouldnt want them too long but a narrow inlet leaves wide legs and a higher cut can be made
stroke and rod length also influence the decision placing more or less load onto the skirt