in our never ending search to extract the utmost power from our scooters we delve deeper into the world of 2-stroke tuning.

i’ll go into further detail about the pro’s and con’s of swapping a 2-stroke engine in a later post. bottom line is the grand axis is fairly quick out of the box with plenty of potential to go faster than you really should on a fucking scooter.

before starting any project you need to do your f’n homework. find some
good lit and feed your head. this book by a.bell came highly
recommended and is definitely an educational read.

i was pleasantly surprised at how easy it is to tear down a 2-stroker. literally it
is three screws to remove the air shroud and four bolts to pull the head and
cylinder which exposes the piston. it takes about 15-20 minutes to completely disassemble the top half
of a horizontal minarelli-type engine.

one of the main reasons for this easy tear down is because 2-stroke internals wear much faster than 4-strokes due to the lack of a dedicated lubrication system. Oil is either premixed with fuel or injected into the engine where it reaches the internals.

carb tuning is an entirely different beast but if you haven’t
heat/soft seized your cylinder at least once, you ain’t pushing it hard
enough…

here is what a stock grand axis 101cc cylinder (left) looks like in comparison to the malossi 125cc cylinder (right).

i won’t go into all the specifics of how we modified this cylinder but most tuners will recognize what was done.

just like a rotary engine all the power is in the porting… we didn’t
alter any of the port heights as we still don’t know how it
will effect the power band and raising it too much will kill
performance but we ported, chamfered and cleaned up the rough casting in the
ports as best we could.

another key component for 2-strokes is the head design. moving to a
squish type combustion chamber prevents detonation and improves combustion by squishing the
air/fuel mixture from the edges of the cylinder towards the ignition source.

from left to right: stock g-axis head, our grassroots modified head (read: we didn’t really know what the fuck we were doing) and cylinder head machined by wind jammers japan.

more 2-stroke gnarlyness coming soon…

b.