Scootering – August 2019

SC

OOTERING

PRA

CTICAL

PROJECT STREET

SLEEPER: PART8

The heart of any two-

stroke motor is its

exhaust, specifically the

expansion chamber.For

me,box-pipes were

hideous things, but over

time my perspective on

this has changed

considerably.

Power hungryyoof
Ialways used to be the guy chasing more
bhp, it was my quest...Iloved the
challenge.Within tuning, the expansion
chamber is king. It can tameamotor with
peaky port timings and deliveratonne of
low-down torque, or it can allow the
engine to sing-on at high revs, and reach
its full potential. Box-pipes, however,are
functional items, built to be robust,
compact and effective... as emission and
sound silencers. But over the years, as we
look back at the classic lines of the
Lambretta scooter,wehave to
acknowledge that the clubman-style
exhaust is part of the iconic styling
silhouette that we lust after.Irecall when
the new LambrettaV-Special was released
and they had neglected to fit the link-style
forks we all recognise in favour of straight
tubed items. An outsider would take the
financial economic gains in that decision,
whereas an enthusiast would take the style
option. So, when it came to styling my
street-sleeper scooter,the original
silhouette is whatIdesired... as best as is
possible when creating something of this
nature. And whenIwas toldaprototype
clubman-style pipe was on its way to me, I
was delighted!

All in... or all out?

When it comes to exhausts,Ihave to be

either all in or all out. By thatImean it

either has to be all about the performance

or all about the styling... no compromise

will do. This wasabit of aproblem when

the first pipe arrived, the one which came

with the engine, because it wasa2-into-1

expansion chamber.That compromise

essentially reduced the spine-tingling

sound of the beautiful purring twin, and

also reduced the power output when

compared toafull set of independent twin

pipes, which would have both sounded

better and given more power! Nobody ever

saw HRC fitting 4-into-1 pipes on to Mick

Doohan’s500cc V4 GP bike. So, if you

want power fromatwin-cylinder,two-

stroke engine... then fit twin pipes! They

look shit hot, sound awesome, and

perform to the best of the engine’sability.

Thankfully,this problem was solved when

both of the other more definitive options

came to market. The 2-into-1 system was

acompromise, whereas twin-pipes, or a

box-pipe, were not. One was all about the

power,the other about traditional/classic

styling. Given this isastreet-sleeper,and

arusteration project, for me it had to be

the box-pipe. No doubt.

The goods

When the pipe arrivedIgot straight on

with fitting.Youknow the job in hand; you

think about it overabrew in the kitchen

before you march out to the garage

clutching the new component. Butit’s

always the same, isn’t it? In your mind it

was abracket,afew springs, andacouple

of nuts in order to get the pipe fitted.

Probablyahalf-hour job, and then I’ll be

back inside for Homes Under the Hammer.

But that’snever the way.Straight off the

bat, Icouldn’t get the bloody double

manifold to slot on to the stubs.Various

lubes were tried... loosening of this,

tightening of that, and then it became

apparent there wasaproblem (isn’t there

always?). The weld inside the manifold

hadn’t been filed down sufficiently,and

was gougingawedge against the stub. It

would never go on. So, it was out with the

Dremel. Problem solved!Well, almost.

That modification did allow me to get the

New box-pipe fromTino for theTarga-Twin

Manifoldhadfitting issues,

Dremel to the rescue

Engine case stud causing fouling

problem was soon resolved

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