I just bought a 2000 RC51. the power on the bottom seems a bit rough and I have been reading about lowering the gearing and running a power comander to help this out a bit.

I only paid $1100 for the bike as it was supposed to have a bunch a wiring issues but it just needed a battery and a couple wires taped up as a mouse had eaten away the insulation of the wire. I was looking at picking up a used power commander as I am into the thing so cheap.

The power commander II plugs right into the ECM so it would install easier. the power commander III has direct injector control and plugs into the injector and a couple other places.

on a stock bike is there any advantage to the power commander III? or should I just get the cheaper power commander II. I can pick up a power comander II for $175 or a IIIr for $200. the only mods this bike will see are power comander and might change the front or front and rear sprockets.

Hi Hognutz,
Welcome !:)
For the little extra $$ between the two go with the PCIII. As one of the biggest issues with the early RCs is the fuelling. The III give a smoother injector setting even better if when you put on different sprockets you get it dynoed & mapped.

The power commander III has direct injector control and plugs into the injector and a couple other places.

Really? I have a PCIII and its a direct plug in. Took less than 15 mins to install.

For the tiny bit extra $$? the PCIII is the better choice.

From the meager info I've been able to find, the PCII was a less sophisticated unit than the PCIII series.
The PCIIIr has the same injector timing connectors as the PCIIIUSB, but also has an extra connector that interconnects with the ignition pulse generator since it had the capability to alter ignition timing.
The PCIIIUSB doesn't have that connector, only the ones that interconnect with the ECU and injector harness.
The PCIIIr is also smaller than the PCIIIUSB, probably almost the size of the PCV.
I have no idea why the PCIIIUSB is so much larger (approx. 30%) than the IIIr or V.

well I was able to get the guy down to $150 on the PCII so I am trying that as I took a wile for people to chime in.

I will see how it goes and if I don't like it I will resell it and try the PCIII.