I had planned on leaving mine stock when I bought it, then I took a trip with the wife and found things needed some improvements. I think I finally have it where I want it, I can pull the trailer and it has power to spare, plus I can run pretty much any gas in it and get away with it.

 

I recently put my 11 back to stock as I had some minor warranty issues that needed addressing. I also wanted to see if I could remind myself why I went through the trouble of modifying the stock exhaust to begin with.

A simple FM headpipe and Ness airbox conversion and 6 months of dinking around with the TTS Vtune trying to get the rear cylinder knock retard from kicking in. As it turns out, the problem was either due to a degraded sensor, or the sensor probe itself not sticking far enough into the exhaust flow to get a proper 02 reading. The sensors themselves were only 4,000 miles old.

All of that effort, frustration and expense just for the 10° to 15° reduction in oil temp that probably could have been gotten just as easily with a simple Jagg oil cooler upgrade. If the fairing oil temp gauge is accurate, I'm running about 250° with the stock setup and a little cooler with the catless headpipe and Ness air box under the same conditions.

In the future, I may put the Ness airbox and a catless headpipe with shorter bungs back on and maybe some quiet performance muffs to see if I can move a little more air through the motor. But with the most recent HD ECM download, I must say that the trike is running pretty dang good as it is and a bit cooler than when I first got it. I'll probably just ride it that way until the HD warranty runs out.

 

If you get curious you can hook the TTS up and record data and see if your still getting knock retard.

 

I was curious and I did because I wanted to compare the 02 sensor data charts both before and after the turn back to stock. When I reinstalled the stock headpipe, I also installed brand new sensors. Knock retard activity is no longer a problem.

 

You see much difference in the O2 sensor activity, you might have had an O2 sensor taking a crap on you.

 

The graphs below show voltage activity on the rear cylinder, both before I changed out the FM headpipe to stock and after. The front cylinder graph data (not shown) mirrored that of the rear cylinder so I assume that if the rear sensor went bad, so had the front. As I mentioned, I installed new 02 sensors when I changed the headpipe back to stock. I had less than 4,000 miles on the original sensors.

Old sensors


New sensors


The help section in data master shows an illustration of what marginal sensor data would look like and it looks a lot like the data dipicted in the old sensor graph above. The new sensor graph shows consistant high and low transitions which also according to data master, is what it should be.

When I removed the FM pipe, I measured the depth of the 02 bungs and they are on the plus side of about 3/8" deep. That puts the nose of the probe barely a 1/4" past the threads into the exhaust flow. Some are saying that you need at least 3/8" to 1/2" to get accurate 02 sensor feedback? For instance, the stock headpipe allows at least 3/8" of exposure into the exhaust flow as I measured it.

I don't know, but if I put the FM pipe back on, I'm going to remove about an 1/8" of material from the base of the bung to put the sensor nose a little deeper into the exhaust flow. I bought a counterbore/spotfacer with pilot just for that purpose. Maybe the extra depth isn't needed, but it shouldn't hurt and if it saves me from having to take the dang exhaust system apart again, it will be worth the extra effort.

To the OP, sorry for the hijack.