Sounds like a cool build, can't wait!

use a degree wheel to set the timeing pressure check engines case ! set pop off to 8psi tillys have to be perfect !!!terry ives has new rods for 101 macs

check pop off pressure on carbs ! use alky and caster oil only 22-24 degrees advance allways do a pressure check on the engine !! lap in all serfaces on glass taped to paper

the flex on the pipe is way to short ! you want 9-1/8 from piston face to the 1st cone or it will run too hot &stick ! alky keeps it cool GEM stack will fit IF you can find one 8 to 10 oz of pure caster pressure check it with your pop off guage

i do not know where vintage terry gets his parts / he is the MAN for mac parts KART engines ! there may be a saw sourse i do not know , terry IS THE ONLY PLACE to buy a new good type of new burris type tapered piston other piston do not have a TAPER in them SO they will stick ezyer oem from mac no taper wiseco no taper terry knows THE MAN who OWNS the only die in the world to make mac pistons, the MAN loaned the die to mr IVES ,i may be off a bit on the info the ives repop of a burris mc piston is what you want to use IT HAS A TAPER! the pistons are slightly smaller in ring area you can PUT a taper in a wiseco or OEM mac piston you measure 1/4 of a inck down from bottom ring wrap eletric tape around the piston then take fine emory paper and sand it down a bit then hit it with 1000 grit or finer it takes time /use a lathe if you have one BUT BE VERY CAREFUL 4 claw chuck is best put about 1 thou in the taper make ring area 1 thou smaller than the skirt this will help it not to STICK ! plus if you use alky for fuel it will help to keep crown of piston cooler get the 2 cycle tuners guide and read it

get a pro to set pop off to 8psi ! hr tilly will work or two tillys get a PRO to set pop off ! popoff MUST be PERFECT or it will not work ! steve O'Hara is the BEST mac engine man for macs !!!! EC birt was best tilly guy but he died steve is a 7 time IKF enduro kart champion he has 65 running macs !