Here's a quick clip of my quick and dirty O2 sensor readout. It's just a bar graph of LEDs for now. There are 16 LEDs that range from 0.0 Volts to 1.0 Volts. The clip is just demonstrative - you have to put the engine under load to get more accurate results, but without a helmet cam or some way to take video while I'm riding that will have to do. My readings look pretty good and are pretty close now with the airbox lid removed. I'm a bit rich in the idle circuit, the mid-range is a bit lean, and the upper end is just about right.

http://video.google.com/videoplay?do...43966805335495

Note how rapidly the sensor changes - when I cut the throttle you can see the mixture lean way out. The center point on the read-out is 0.5 Volts which means all the fuel was burned and all the air was consumed. But the experts say you actually want to be a bit rich for the best power so I want the result near the top, but not quite at the top.

Note that it is Version 1 - I don't intend to leave this on the bike as-is. When I make something more permanent, it will be a bit more refined and not bungied onto my crossbar. But this is good enough to let me know where I need to tune the carb.

 

Just to follow-up on this, my sensor has done its job. Based on the read-out providing confirmation of the mixture at various RPM and engine load, I've got my finicky Keihin FCR dialed in very well now, at least based on my first test run. When I first had my dyno run, the results indicated that the bike was running rich across the board, and in the RPM zones where it wasn't running ultra-rich, one could not a noticable bump in both HP and torque.

I posted on Thumpertalk to the "Jetting" section and the TT jetting expert, Eddie, recommended leaning everything out, but putting in a more agressively tapered needle. Not having the jet sizes nor the needle he recommend, I did the best I could and dropped the jet sizes by 3 from 155 and 55 to 152 and 52 respectively. Eddie recommended 145 and 45 so I was still a pretty long way from what he recommend. Even so, I did notice a better response, especially if I removed the two snorkels from the airbox lid (double snorkel mod). And that was my setup with my first run with the O2 sensor installed and it was still showing pretty rich, though it was better.

Just recently, my jets and needle came in that Eddie recommended and I changed those out today and installed the new ones as well as reinstalled my snorkels in my airbox. What was immediately noticable was that the bike seemed to idle much better and I didn't have that hanging idle condition that I had before. Occaisionally the bike would stall as I opened the throttle, i.e., at a stop light or similar. While I don't have enough time on it to know whether this is solved, the engine definitely feels more stable at idle and doesn't feel like it might do that. As one would expect, the O2 sensor indicates a slightly less rich level at idle - about 0.8 to 0.85 volts. On my test spin, my O2 result stayed slightly less rich than it was with the previous set up, again, staying around 0.8 to 0.85 volts which is right in the range that the experts recommend for a good mixture. Power is still good - those no-clutch wheelies still work well, perhaps a little better. Similarly with 2nd gear - I can bring up the front in 2nd with no clutch with a little tug on the bars.

I now get a little bit of a pop on deceleration, but I think that is normal. I wasn't getting any before and I think it was just too rich.

Anyway - I'll probably leave the sensor in place for a while until I'm sure I have it dialed in where I want it. I've basically followed Eddie's advice (the TT jetting expert) and it now seems to be very close to dialed in, much closer than before. And the O2 sensor comfirms it.

 

Sounds good, wish i could do that... thats the best way to get it right i believe. Glad its all better, so you have your air box lid back on? So i guess it its better, when it comes to a/f ratio, to have the lid on.... Sounds good brian, glad its all dialed in.

 

Yeah, I put my lid back on. I do have the high flow snorkel as well as a cut down version of the stock snorkel for even more air flow. Before I was running with both snorkels pulled so I just had the two large holes in the airbox lid. I didn't notice any difference in the O2 sensor readings between that and running completely without the lid. And ... in light of Tony's experience with his lid / snorkel, I don't think there's a whole lot of airflow difference between running with the double-snorkel vs no lid at all. I'm sure there's a little, but I don't think I can tell the difference. So I just put it back on.

Besides, that will give me a little bit of "adjustment" if I ever ride somewhere higher in elevation. Since I don't have room for one of those fancy fuel screws you can adjust with your fingers, I'll at least be able to pull the seat and remove the airbox lid for a little bit more air.

Here's my lid: