Triumphrat

GrandPaulZ

(asked in a PM)

This all goes to your intended use.

For racing, lighter is better.

For everyday road use, heavier is better.

In racing, you want the engine to have fast response and spin up to high revs very quickly. Lighter flywheel allows the engine to spin very freely on accelleration, and drop revs very quickly on decelleration (for engine braking effect). Normal decrease of efficiency in engine tuning (carb, plugs, points & valves) over time is magnified and amplified in free-spinning engines; so, you must keep it in finer tune or it will be more quickly noticeable.

On the street, you want the engine's intertia to remain as constant as possible for smoothness at idle and typical road speeds. A heavy flywheel requires less throttle at idle and gives a more predictable feel on accelleration and decelleration. A steady spinning heavy-flywheel engine is somewhat more forgiving of normal decrease in efficiency over time; you won't notice the need for minor valve adjustment or new plugs until it's more pronounced.

That's my additional 2 cents...

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GrandPaulZ
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Tiger Dale

I totally agree.

TD

jimmy bush

Unless of course you like your street bike to have the lively response of a race bike. I might be a crazy old fart but I'd like mine to be able stand straight up if I wack the throttle too hard. It won't of course but I'd like it if it could. There is some guy on the Hinkely twin forum that is getting 112hp at the rear wheel of his New Bonneville. The bike is supposedly docile enough to be comfortably ridden on the street unless you get crazy with the throttle, then you'd better be hanging on. I think that thing would be a gas to own/ride. I would like to do some of his mods to my T100, maybe about 80 rwhp worth but that's just me. (Hey, you said is was for argument didn't you?)