ignition module problem
Your original post and description sounds just like mine, rear cylinder misses about every third time and kind of pops, mine only does it when cold. I had a long thread about this last year and tried quite a few things to no avail but since it only does it at idle and evens out when warm I'm ok with it.
Here is what I tried, all new intake rubber, carb serviced and rejetted a few different ways, compression good, leakdown excellant, SE wires and coil, check all electrical/ignition wireing, few different kinds of plugs(autolite coppers are great), changed the exhaust-(not related to issue). One thing I noticed on mine was the rear cylinder runs slightly richer than the front and like most EVO drivers, I maintain cold idle with the throttle lock and not the enricher, keeps the plugs cleaner.
None of what I tried fixed the rear cylinder issue and even when I fixed my intake leak there was no change. Did you put a cam in your's, just currious. If you get it fixed post back what it was, that would give me something to mess with this winter.
Doug
Here is what I tried, all new intake rubber, carb serviced and rejetted a few different ways, compression good, leakdown excellant, SE wires and coil, check all electrical/ignition wireing, few different kinds of plugs(autolite coppers are great), changed the exhaust-(not related to issue). One thing I noticed on mine was the rear cylinder runs slightly richer than the front and like most EVO drivers, I maintain cold idle with the throttle lock and not the enricher, keeps the plugs cleaner.
None of what I tried fixed the rear cylinder issue and even when I fixed my intake leak there was no change. Did you put a cam in your's, just currious. If you get it fixed post back what it was, that would give me something to mess with this winter.
Doug
OK so I just switched the inputs to the coil and left the spark plug wires alone. Now the fluctuation on the vm is on the front side and the rear is steady. The front cyl is running perfect and the rear is still stuttering, so that's not it. Also when i put my hand over the front pipe it always pushes out on my hand but on the rear pipe it i feels like it pushes out but in between puffs it sucks my hand up to the pipe. What can cause that?
Last edited by miacycles; Oct 27, 2010 at 09:48 AM.
I have a stock cam. I think I'm gonna put a single fire ignition in and see if that helps, sense the pistons don't fire exactly opposite of each other maybe the dual fire is making the rear cylinder fire on the compression stroke or something IDK, just guessing. I watched several of the videos of other members sportsters on here and they all sound the same. I would like to hear one with the signal fire for comparison. I'm just the kind of person that if something seems wrong I have to make it right, just so I don't think about it all the time. I have a buddy with a 05 dyna and it sounds perfect at idle, doesn't miss a beat. I wonder if it has single fire ignition? I'll check into it.
It looks like dual fire does cause a problem. I found this in a google search. http://www.daytona-twintec.com/tech_evo.html
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