I`m not sure how that setup effects intake, exaust return so to speak etc...
plus, who knows the quality of your gas (premium with ethanol? lame old station lacking decent filters, hence, posible stale gas etc)..
I`d just suggest starting out FAT and work your way down by what the plugs tell you on a good lil run..
be sure to start out fat enough that you dont actually burn it down on the first test run..
try the stock jets to START OUT.....see what the plugs read after a run...also keep in mind the temps during that first run...if it`s fairly warm out considering...thats gonna make a huge difference compared to a run when it`s VERY cold out..
the thing is..it`s scary to suggest actuall jets, considering all the variables..and no one wants to be responsible for suggesting what jets to use and end up having a guy report back that he burnt down...
as far as that goes, even starting out with fat stock jetting, could result in a burn down if you had an air leak at the crank/case area, intake leak, dirty carb/s, alotta moisture in your tank from setting etc.. maybe even a real bad pipe/ to head connection?..
just play it safe at first and work your way down..
jets are ALOT cheaper then pistons, cylinder replating, and posibley even worse damage due to a lean condition...
and again, remember temps WILL play a big role..a good plug reading when running on a 20F day, may read lean on the ragged edge on a minus 10F day...just for example..
if/when you get what looks to be the perfect plug reading..Firgure your safe for about a 10F maybe 15F change in temps either way...much more then that, is questionable at best...
the perfect plug read at 20F, might mean a burn down at -10F on a decent hot run..