So I have gotten a PCIII not too long ago and the mpg dropped from making approx. 150miles before the reserve tank light kicked in to about 140. After getting new chain and sprockets (15 in the front, 46 in the rear) and installing speedodrd the light kicked in at 127 today. Is this normal or should I worry?

 

When was the last time you changed your air filter? I had my reserve kick on at 87 miles when I first got the bike. The filter was a sight to behold, I'm surprised it ran. I changed that and modified my riding habits and the next time it came on I was sitting at 160 miles or so.

 

I would try a couple tanks before assuming you are getting less mpg, it might have just been riding harder.

 

Modern sport bikes tend to have lean air:fuel ratios to help meet pollution control regulations and improve gas mileage. Whenever we add aftermarket exhaust and air filters it allows the engine to flow more air which means we need to add more fuel in order to maintain the proper air:fuel ratio. That's what the power commander is for, it adjusts the air fuel ratio. They can be tuned , through the use of "maps", to provide better performance, or if you wish, better mileage.
I'm not saying that your mileage issues are definitely being caused by the PC III, only that some reduction in mileage is to be expected when adding more fuel to the air:fuel ratio.
Your gearing change is also going to negatively impact your bikes mileage as well.

 

As sparkman said, there are intentional lean spots in the OEM fuelling to meet emissions regs, PCIII will override these.

Also, the speedo drd will make your speedo accurate which means your odometer will count miles up accurately, it could be that your speedo was over reading before so miles were racking up quicker than you were actually doing them. If you have altered the gearing too then this would alter your MPG. Do a couple of tanks before you take it any further and try and do similar journeys at a similar pace to before. On my commute I get 150 miles out of a very full tank, on a weekend I get anywhere from 100-130, how you ride it makes a big difference.


When your light comes on, how much fuel goes in until the tank is full (i.e. bike upright not on sidestand, fuel all the way to the filler cap)?

 

Good point. I got a brand new K&N air filter that I put on December 21st, 2010. Is it possible that it would get that dirty over this time?

 

I will do more fill ups and see what I get next time. The two fill ups after changing the chain, sprockets, and installing speedodrd gave me 127 and 133 miles at the time the reserve kicked in. When I go tank it, I roughly put 3.5 gallons in (bike on the stand, all the way to the cap). One more thing I should mention, I am putting 87 octane fuel in, because I was told it is better to do so.

 

I have a 97 600 F3, so far it dies out on me at 130 miles then i have to switch it to reserve... this normal and if not, what is?

 

Ok, so before my last fill up and the reserve light coming up my bike did 117 miles. that gets me worried a bit.

 

I noticed about the same amount of drop in my mpg when i installed my pcIII. My range is around 130 - 135 and the light will come on. I don't ride mine hard most of the time. Just every once in a while. A friend of mine gets about 125 no matter how he rides. (most of the time really hard)