Tom Mathews' tuning info:

"custom exhaust"

The engine is stock with a needle kit, running Uni filters instead of
the stock airbox. Ultimately, we ended up at 160F/158R mains, 45 pilots,
needles in middle position and A/F set at 1.5 turns. She idles very
well with a responsive throttle, A/F ratio hovering around 13. She's
making 54 HP and a nice flat torque curve at 41 ft/lbs, repeatedly at
750 ft above sea level. Keep in mind that i am running about 30 inches
of additional exhaust length over stock, creating a bit more flow over
a standard stubby, so your mileage may vary...