Heavy Duty – July-August 2019

TECH TORQ

MELBOURNE MOTORCYCLE HIRE & TOUR

LIVE MORE. RIDE MORE!

H-D, Triumph, BMW.

ph: +61 3 9870 1730

eaglerider.com/melbourne

email: [email protected]

401 Maroondah Highway, Ringwood, Vic

the very impressive figures of
122.65 horsepower and 107
Newton metres (78.9lbs/ft).
Hoody sent me an update
when I told him about this
question saying, “Interestingly
the original engine out of that
thing is still in Dan Dycer’s sand
drag bike. It makes over 145hp
on nitrous and is probably one
of the fastest and race winning
bikes in its category.

SPORTY VS
BIG TWIN
Doc, my brother Ralph
inherited an Sportster Iron
and is thinking of trading it
for a Big Twin as he wants a
faster bike for Sunday rides.
And because his mates tease
him about Sportsters. But he
does enjoy riding it. What do
you advise?

• Milo

Okay, the fact is a Sportster,

given the same horsepower,

will always leave a Big Twin in

the dust. It is called power-to-

weight ratio boys and girls.

Take, for example, a Fat Bob

and a Sportster lining up. The

Sportster Iron, for example

comes in at 247kg, while the

Fat Bob hits the scales at 304kg

and the Heritage at 316kg, a

difference of around 60kg in

the case of the Fat Bob. It’s as if

the Big Twins start out carrying

a pillion passenger – even when

they don’t. Okay, so not all of

us are dating supermodels, but

these figures should make the

point.

Think of the last time you

picked up a 60kg dumbbell

at the gym. Heavy mothers

aren’t they? Adelaide Harley-

Davidson Bike Works installed

a Screamin’ Eagle Stage IV

Street Performance Kit on a

Sporty motor. The kit includes

CNC-ported cylinder heads

with performance valve springs,

SE XL SE-585 cams, forged

hi-compression 10.5:1 pistons

and rings, a 58mm throttle

body and intake manifold, and

a top end gasket kit. Plus dyno

tuning. 102.78 prancing ponies

and 84.17 lbs/ft of torque

makes this a flyer, ready to blast

off many a Big Twin!

CRANK RUNOUT

Doc, I have a concern regard-

ing your reply about the S&S

gear driven cam conversion

question in a previous issue.

I was thinking of this and

I asked my dealership for

Power (hp) / Torque (ft-lbs)

ADELAIDE HARLEY-DAVIDSON BIKE WORKS

Engine speed (RPM x1000)

125

100

75

50

25

(^0) 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7
■ Max Power: 102.78
■Max Torque: 84.17
Above: The dynograph shows the results achieved by a Sporty motor with a Screamin’
Eagle Stage IV Street Performance Kit.