Softail dynoing lower then Dyna chassis

[mtkawboy]

Had my bike dynoed at Beartooth Hd in Billings Mt a while back. The guy was telling me my 95 Fatboy would be down 4-6 hp with the same mods in a Dyna chassis because of the way the shocks work backwards. Anyone know if theres any truth to this ?

[BVBOB]

Originally Posted by mtkawboy

Had my bike dynoed at Beartooth Hd in Billings Mt a while back. The guy was telling me my 95 Fatboy would be down 4-6 hp with the same mods in a Dyna chassis because of the way the shocks work backwards. Anyone know if theres any truth to this ?

The reason is more likely that the softail has to turn the balancer assembly in the B motor and the Dyna with the A motor does not.

[mtkawboy]

This is a 95 EVO motor in a Softail frame, no balancer

[Tech23]

Originally Posted by mtkawboy

Had my bike dynoed at Beartooth Hd in Billings Mt a while back. The guy was telling me my 95 Fatboy would be down 4-6 hp with the same mods in a Dyna chassis because of the way the shocks work backwards. Anyone know if theres any truth to this ?

I think maybe you misinterpreted what what he was trying to say.......if not I would keep an eye on him, and see if he pokes his eye out using hand tools.

[Totenkopf]

A Softail chassis / swingarm with the undermount shocks, during maximum power, consumes more of the drivetrain power than a Dyna chassis setup does with the external over shock configuration. Like for like, it can be as much as 5 - 8 hp difference on a chassis dyno. The two chassis styles react differently in terms of power transfer.

A rigid frame is the most efficient for power transfer and is what we use for racing. To get traction we use low pressure in the slick so the chassis squats when the slick wraps and then wheelie bars set correctly to keep the slick planted.

[mtkawboy]

Thanks for the answer, no I didnt misunderstand him. We spent a ton of time talking about it. He told me an average stock softail EVO made 48hp and a dyna 54 hp

[Colonel Sanders]

Tote, could you explain a little more what's taking place with a softail that causes it to soak up more power on a dyno. I get the initial launch at the strip being softened by energy being transfered and dispersed by the shocks but after the initial hit when the suspension becomes more or less static (more so on a dyno) why would the suspension continue to soak up HP? I mean, at that point you have a belt turning an axle that is stationary in either case so what would be the difference?

Perhaps some part of each power pulse is moving the suspension and therefore being dampened? But wouldn't how much is absorbed simply be a function of how soft the suspension is set rather than what type of suspension is used?

Thanks, Tote.

[Colonel Sanders]

Watcha think, Tote?