I just bought a new tuned pipe , and the inlet to the pipe is about half the size of the exhaust port of the engine . Is this right ? Should'nt there be free flow from the engine to the open chamber of the muffler ,then have a restriction at the exhaust part or tip of the pipe ?

Here is a picture of the pipe in question !

If the header fits correctly its probably right. If the header is smaller than the exhaust port then no.

The muscle pipe series by Curtis Youngblood give the power of a pipe w/o having to mess with header length to get them tuned right.

Oh it bolts right on ,but where the exhaust comes from the engine , is a larger hole than where it goes into the pipe . Like the exhaust will have trouble getting out of the engine ,into the pipe.

Sounds like you have the wrong header.

What he means is the hole in the header is smaller than the large port on the engine. Even though the header is the right size. This is common in all my previous RC glow experience... Just about all headers (non round ones at least) have a smaller opening in them than the large square port on the engine.

I know some people dremel or mill the opening larger, others leave it as is. I don't know which is best, but until i see real evidence to say milling the opening larger is good i'll leave it as is.