Some people put them in to supposedly help cure an off idle stumble. Some think it helps... others not. I personally don't think it does anything for performance and will cause you to need to use a higher octane fuel to keep it from pinging.
Do a search - There have been several threads in the last few months that got in to this discussion. I think the majority ruled it 'do it if you want, but the value versus work versus advantages' make it a more than likely not.
Or I may remember the threads wrong. I am old.
I had one, gave me a nasty flat spot at about 2K, got worse gas mileage, and made me have to run higher octaine (when the 4 degree first came out they said to run premium, then later said you did not have to, and yes I did test with regular too).
Did not notice any 'extra power'.
The best use for it, IMHO, would be to throw it at someone if they were messing with my bike.
They work -- the crankshaft key is relocated to advance ignition timing by 4-degrees ...
... the larger question is what would advancing 4-egrees do for you and your bike?
Typically the advance would remove some of the low RPM power (if you remember the older distributor systems low vacumm retarded ignition and low RPM kept the mechanical timing advance to a minimum -- to produce greater power for high-deman at low RPM). If the older distributor systems functioned correctly, then adding 4-degrees of advance full-time would not be something of interest for low-RPM and/or high demand (low-vaccum) situations, right?
They do work to advance the base-line reference for the ignition timing, but as many have said, they can provide too much at times, and can tend to reduce lower RPM power.
From personal use, they seem to help in cruising mid-band area, though I've not seen any milieage increase, nor could I provide any 'real' data other than the seat of the pants towing feel at about 2750-3300 RPM.
It'd come down to the personal decision in if you need/want to advance your base ignition timing 4-degrees, but the design and implementation do 'work' (advance your ignition timing)
That's kind of what I thought.The reason I was thinking about using it is, I just converted my 1500 wing over to a trike and since I'm now moving more weight, I thought it would help . But is it worth it. is the question???