Transfer Port Question

[Johnc(ks)]

I've seen several threads where transfer port designs were discussed, and I have an ignorance-based transfer port question for some of the 2-cycle experts. What is the difference between "open" transfer ports and "closed" transfer ports? I'm assuming that the transfer port is the passage that is either milled or cast into the cylinder that transfers the air/fuel mixture from the crankcase to the combustion chamber sometime during the power stroke. Thanks.

John C.

 

[bwalker]

I believe the term open refers to a transfer port that is a simple groove in the side of the cylinder that uses the piston as one of its walls. Closed on the other hand has a duct cast into the cylinder that goes from the crank case to the upper end of the barrel bypasing the cylinder itself.

 

[Philbert]

I was wondering this as well and found this thread. Is this the correct answer: 'Open' transfers are recessed into the cylinder wall and 'Closed' transfers run outside the cylinder and enter through ports?

Thanks.

Philbert

 

[Nardoo]

Exactly. Closed port cylinders are said to be more powerful and also better for modding. Generally open port cylinders are found on more inexpensive saws.