If you go to Ed Hartley's page, you can see a lot of different OS1.40 set ups. http://www.rcpattern.com/2cycle.htm

I used a pipe for a while, but the last two planes I have used a Bolly 590 muffler. No set up or tuning with a muffler. Mine turns a 15,5X12 4 blade at over 7,800 rpm on 15% fuel. Plenty good for most 2M's. I'm half convinced that by the time you make a tuned pipe long enough not to have a noticeable"peak" that you lose much of the benefit of a tuned pipe.

Great info guys,

I too own a 140RX that is still in the box, the plane is not ready yet.

Any tip or procedure for tuning the correct distance of the pipe?

Good point, Jeff. Also, it helps remove the midrange 'burble' (richness).
Me, I shorten the pipe, fly the whole flight at full throttle and can fly the FAI P05 sequence in 5 minutes - kidding!!

And the muffler is a lot shorter!!
-Will