When I first put my PCIII on my bike after doing the big bore kit in 2009 (2008 TE 250 with power up) I spoke to someone at the Power Commander facilities technical help group to try to get an established map, but since mine was so new at the time they had none. The person was very helpful and when I told him one of the problems was terrible backfire on decelleration, if I remember correctly, he said to add fuel in the "0" throttle colume. I had the bike running great for 2 years and near the end of last season I noticed the backfire was coming back. This off season, I adjusted the valves - 3 of the 4 were at the top of their range so I replaced the shims with thicker ones to get them in the middle of the range. The bike seems to run stronger, but unless it's my imagination, the backfire on decel is even worse. Before I tweak my map and experiment, I'd first like some input....is my memory correct - add fuel to the "0" throttle colume? If so, explain what's happening and why this fixes it...I have a theory, but want more feedback. Thanks.
yes, adding some fuel in the decel and 0 throttle positions could help. this is curing a slight lean condition in those zones. before adding any fuel, make sure all your exhaust connections are secure and not leaking. if you have a loose header, for example, that slight bit of air entering can cause a 'lean pop' on decel.
Well, Sunday afternoon it finally got into the low 50's and all the snow's gone, so I figured I get the laptop out, review the latest printout of my fuel map, and get this sorted out. The fuel that's in the tank is out of a 5 gallon can that I bought at the end of last season from a place that had 93 octane non-ethanol gas which I added fuel stabilizer and a small amount of 2-stroke outboard oil to. This is the same gas that was giving me the backfire on decel problem. I shook up the gas can and topped the tank off on the bike and fired it up to warm up. I switched the dash to read RPMs so I could take note at what point the backfiring was happening. My latest fuel map has 2% in the "zero throttle column" up to about 4,500 RPM and then no fuel in the RPMs above that. My thoughts were that if it backfires at zero throttle at 5,000 RPM and above, I would add 2% fuel to those areas too....makes sense. When the bike was good and warm, I took it out and tried my best to get it to backfire but couldn't...at any RPM. Could what I'm experiencing be the result of humidity in the air and air temperature? The last time I had the back firing it was colder and drier and now it warmer and moister. The bike didn't seem to have quite the power as it had when I was experiencing the backfiring either, so all these would point to a slightly richer-running bike, right?
