HarleyTechTalk

rear cylinder not firing as good as front. I can unplug ICM and wait a few minutes and plug back in and cylinder seems to fire and hit like the front after a few minutes running it goes back to same problem. I can feel almost no heat or pressure at end of pipes on rear but front is good and never changes. I change to carb from EFI several years ago. every one says this is not possible !

2004 offered EFI and CARB versions so when I changed I ordered wire harness from factory and changed ECM to ICM. S&S carb and intake, intake had place for map sensor and wiring harness had a plug so I installed sensor. Just unhooked map sensor and timing issue is much better. will not using sensor hurt anything?

Just to start off I have no experience with your conversion. 
First question has it been running fine with the map sensor hooked up for the last year that the conversion was done?
My thought is that they are using MAP sensor input for timing curve input.
When rear cylinder dies do you still have spark to rear cylinder?
Second thought when you say when it happens no pressure or heat from rear pipe I would think you should still have pressure even if you did not have ignition, the rear cylinder should still be moving air in and out. Unless valve was sticking open.
use a spark tester when it is happening, you can even hook between spark plug with the alligator clip and other in the sp wire while it is running and see if you are getting spark to the plug. use the type that you can actually see spark jump the gap and not just show a light.
like this one.
http://www.autozone.com/test-scan-and-specialty-tools/ignition-tester/great-neck-adjustable-ignition-spark-tester/10257_0_0/
also when it does it shut bike off and do a compression test as soon as you can before it cools down.     

Do any work to pushrods lately, could be an adjustable slightly to tight. Heat makes it expand and not close fully, no compression no spark, just a thought.

I did a cam change, but this was happening before. Sensor seems to change timing curve, with it unhooked it sounds good but sluggish under acceleration. plugged in sensor and acceleration is good, went for another quick spin and twisted hard on throttle, ran good but does not seem to go back to time and fires weak on cylinder at idle. feels and sounds like it fires on one cylinder. Looked for intake leak but none found.

Quote from: 04wideglide on May 26, 2015, 05:56:12 AM
I did a cam change, but this was happening before. Sensor seems to change timing curve, with it unhooked it sounds good but sluggish under acceleration. plugged in sensor and acceleration is good, went for another quick spin and twisted hard on throttle, ran good but does not seem to go back to time and fires weak on cylinder at idle. feels and sounds like it fires on one cylinder. Looked for intake leak but none found.

  The map sensor is supposed to change the timing.. Not sure what it's causing a weak cylinder pulse but sounds like you might want to replace the MAP sensor... If you remove the MAP, the ignition module will pick the slowest curve.. In the case of the front cylinder hitting hard and rear not, it probably has a little too much timing at idle.. Make the front cylinder hit hard enough that the rear doesn't have any load on it.. Irregular firing pattern. I've not had this type of failure tho so I'm guessing.. I have had one cylinder hit not as hard at idle on a non MAP ignition due to timing tho. 

Thanks for the replies. On going Mystery, once it advances or retards don't know which, I am guessing but around 20% loss of power in general. Can unplug and start process all over. Thinking on Dynatech type module but don't know if it will fix it