I drilled holes in a plate to create a flange, later if I end up using this
flange then I will shape it to look more like the factory flange and to
further reduce weight.

Tricky part will be merging the 2 pipes into one to form a make shift Y pipe
then to mate it to an expansion chamber maintaining the true length of the
factory pipes.

While waiting for theat manifold and carb to get here I started to play with a pipe,
using the body of an old stock Pilot pipe I figure I need to fabricate a Y pipe
something like this, where the heck is that intake and carb I cant go on until
it is here grrrrrr

would it not be better to direct the flow of gasses more towards the exit of the pipe to help reduce turbulence. Looking at the picture the pipe on the right seems like it should point more towards the right. I dunno, maybe this would change the header pipe length for that cylinder too much, but it seems like you would get better flow that way.

something like this maybe

I don't know all the details or specifics but the "Y" needs to be the same length of pipe on each side. Kind of the same way the best headers for a car are "equal length headers". If memory serves it's to make sure the pulses arive at the same time or because one helps to pull the other out.......I guess you could look at it as simple as both cylinders need to have the same size and length of tuned pipe, other wise one side may be more or less in tune! Like putting a Rev pipe on one cylinder and a torque pipe on the other.

Hoser why don't you try to contact the guy that got the pilot with the 600 Rotax on eBay, or the one who built it (pilotdude most have his info) if is the same pilot he might have the Stock pilot pipe the one on your pictures, and offer to buy, looks like a nice/clean setup don't know if it will fit your Engine but on the pictures look like it.

If it works look like a less headache too me

Odykid

Check out the length on these factory manifolds hehe

I need to get it running before I worry about building a 400-600 custom pipe
I would look kinda silly spending 400 bux on a pipe only to find out the whole
ignition system is fried and needs replaced $$$$ or the crank is twisted and needs
rebuilt$$$ don't worry I didnt have any problems keeping up with the Pilot Engine
this one should be able to keep up even with my billy-bob pipe hehe

Going back the other direction like I had drawn was to keep the true lengths closer to the same length

in your picture with the drawing the left cylinder "headeer" points back up the pipe from the right cylinder. I was just worried about turbulence more than tuned length since a "tuned pipe" will be hard to get with this setup.

Yeah my drawing is kinda crude I will be cutting a 45 ? and point it to the left then
about 3/4" straight then another 45? to the right the idea is to use up length the
gases inside the pipe will merge together parallel where they enter the pipe
if I take the route you have drawn it will be shorter than the other side either
way I am sure it will out perform the old style canister mufflers that came on
sleds heh

Ok the manifold I won off of Ebay (thanks Stoneman) finally arrived today
so I am able to resume locating the Engine, the rotary valve is driven off a
gear on the center of the crank , the gears are lubricated with its own oil
and there are oil circulation lines to the oil tank, the top line is going to hit
on the carb but I think the tube can be modified for clearance, maybe it
can be bent I wont mess with it until I take the Engine out again to weld
up the Engine mount, once it is on the bench I will work on it, worse comes
to worse I will have to take the head and cylinders off to modify it.

The bar between the Engine and trans is ( Aluminum bar with the stock center to center
distance and using shims got the proper offset) is working great to maintain the correct
belt alinement.

New Engine mount III

More on the Engine mount http://www.pilotodyssey.com/PO/viewtopic.php?t=744