mc21 frame ( with aprilia rs250 mk1 front suspensions and brembos)
sp front wheel. the back is 17' but not sp yet
lightened to about 122 kg with a little fuel in.

keihin pwk38 airstrike carbs,
open carbs
velocity stacks
aluminium 38mm short manifold
tyga hi-flow reeds.
heat-shield

ported crank-case
epoxy to the oil pools like honda rs models.
stock pistons
mc21 r model cylinders
2 top cylinder sp heads..
0,4mm cylinder base gaskets
ported exhaust ports (to get more wide and more height,tryed to have as flat posible the top of the port like mc18 cylinders)
8 heat range sparkplugs

power valves are always 100% open (pv mechanism removed)
lightened mc21 flywheel,lightened clutch.
kickstarter and mechanism removed,no oil pump

jha mc18 1989 exhausts with exhaust wrap
mc18 1988 pgm1 electriks (aprilia rs 250 coils)
engine is mc21 but i fit a 1989 mc18 gearbox (and clutch is 1989)
gearing is 14-40 feels short but builded for small tracks. probably because the 1989 is one of the most short gearboxes and also designed for a 18'rear wheel.

pulls nice from 7500rpm and you can ride it at low rpms with no problem. (this is good,remember power-valves dont work)
it get's to a mad pulling at 10.000
rpms get very fast up to 12.500+ max rev is about 12.800- 13.000 (clock readings)
from 2nd gear and 10.000rpm to 4th gear and 12.500 it takes about 6 seconds or less

smaller diameter front spockets may produse more chain and spocket wear.


next engine will be with
some crazy ported mc18 cylinders
2 rm125 single ring pistons, skimed mc18 heads
and the right exhausts for over-rev
16-40looks good if there is posible to fit a 16 spocket.