Velocity Stack Issue?

[TonyJ]

I have a 89" Chopper with a Mikuni 45 and a Joker Machine Velocity Stack. It has 3.13 gears. On the highway, at about 70mph in 5th (about 3000rpm)(Im guessing, no tach, no speedo) when I give it a little gas, it detonates. Happens when its 50 degrees or 100 out. I have retarded it, tryed different brands of fuel, the normal stuff. Plugs are good in color. Has a Twintec ignition.

Does anyone know if there are any known issues with velocity stacks? Is it possible that at speed it is leaning out due to design?

I will be taking it to my tuner to have him check out the curves on the computer but I have always had this issue, even when I change the curves manually. Dont really want to put on a "traditional" style air cleaner, but might have to. Bike runs great thru all the gears, this is the only issue.

Thanks


Other details
Allen Johnson Heads, Viper Plus Cam, Wisco Pistons, bike weighs 525lbs Ignition is now about 4 degrees before tdc

[tx_shooter]

The only issues I've heard of with velocity stacks is with the lack of a good screen available for most stacks. If the stack has a decent flowing screen it should help out with air quality and flow. A buddies bike ran decent with the stack - but ran better with the basic little screen. We never figured out why - we just went with it.