Daytona.

Laconia.

port.

When we first announced 5-port

power, we got mixed reactions:

‘‘Hmm... really... good

for you ... yawn."

Since then, we've visited

a few race tracks.

(Daytona: 7 out of the first

10 places in the 250cc Race.

2nd and 3rd in the 200 Mile

Classic against machines twice

our size. Laconia: 8 out of the

first 10 places in the 75-mile

Expert 250cc Final. Mosport:

1st in both the 250cc and the

Open class.)

Suddenly, everybody’s interested.

Here’s the difference with 5-port power:

In an ordinary 2-stroke engine, burnt gases

at the top of the combustion chamber keep

the fresh charge of fuel from completely filling

the chamber. Some of the fuel goes straight

out the exhaust port.

5-port power puts two extra ports at the back of

the cylinder. Fresh fuel swirls up into the top of the

chamber (not out the exhaust). All the burnt gases are

pushed out. The chamber is completely filled with fresh fuel.

Note: Isle of Man: England world Championship

250cc Class— first place, Yamaha.

125cc Class—first place, Yamaha.