"Many moons ago, I'd already breathed a
bit of life into Paul's MC28 250cc motor, but eventually he saw the light and
wanted a 300cc. He ran this for a while in 'stock' form and life was good.
However, Performance by name means performance by nature, so out came the engine
for a bit more surgery.
It stayed as a 300cc, but I spent a few
hours on the cases with some epoxy here and some grinding there to assist flow
and pumping efficiency. All the 'dead' space in the cases, such as the oil drain
pockets and behind the reed valves is filled, and then
re-contoured.
The mixture is fed into the cases
through modified (bored and polished) HRC kitted MC28 carbs, and
controlled by TYGA Hi-Flo reed valves fitted with HRC RS125 'A' kit carbon
reeds. Foam filters keep out the small children when it is on full
volume.
The cylinders were stock, so another
couple of days saw their transformation with completely new port timing, time
area and angles. Wiseco pistons replaced the stock items. These US made slugs
are lighter and stronger than the stock pistons, so it lets the engine rev
faster and harder. The big bang is controlled by the very efficient VHM heads,
which are designed for a tighter squish clearance and a chamber more biased to
the top of the rev range. The mixture is ignited by RS250 plugs and
caps.
A lightened MC28 flywheel is fitted to
further assist in engine acceleration.
The gearbox has also had some treatment.
The primary drive and driven gears are lightened, as is the clutch hub and
basket. The transmission plate is modified to fit an extra needle bearing for
the shifter shaft to enable smooth and silky gear changes. The clutch
itself is beefed up with out TYGA dry clutch rebuild kit.
Setting up the carbs on the jungle roads
near my house is a little tricky, but the locals love
it......probably.....and I've totally lost count of how many people ask me if my
fuel's run out, or the spark plug fouled as I push home after another plug chop
:-) "
