Flame licker phasing

[tornitore45]

I am about to finish the Lanz tractor. I am at the point where I want to check the engine before the final assembly because is a bear to disassemble.
My question is: What is the correct phasing to be at least in the vicinity of right.
At what % of the down stroke should the port close and reopen? Obviously the two event are related by the cam shape but they can be moved together.

 

[Brian Hutchings]

On my Poppet, the inlet commences just after bottom dead centre so that the flame is drawn into the cylinder and the valve closes just before top dead centre to allow the vacuum to be created by the cooling down of the cylinder.
Brian

 

[tornitore45]

Brian, thanks for the answer but can not visualize how the timing you show work.
If the inlet open just after BDC the flame is blown out as the piston travels to the top. Unless there is considerable vacuum as the piston ascends, enough to suck the flame instead of blowing out.
It seems to be very counterintuitive.

 

[Brian Hutchings]

Sorry, I got my BDC and TDC mixed up!
The valve opens just before TDC so that the flame can be sucked in as the piston decends . The valve closes just before BDC so that the vacuum, caused by the heat being removed, can bring the piston up to TDC to begin again.
The valve open and closes slightly early to allow for the speed of the engine. On my Poppet, the cam is just loose enough to allow adjustment but not so much that it would move in operation.
Sorry for the confusion and I hope that helps.
Brian

 

[tornitore45]

Now we are cooking. Is what I thought but somebody mentioned having a lot pf problem finding the correct timing I wanted to hear someone that had an engine working.
Is a good starting point.
Thanks
Mauro