Need tech advice on twin cam 96" 08 street glide. Purchased a Zippers thundermax w/ auto tune, bike ran excellent for short while, then started coughing back through the intake on acceleration starts, usually from a stop or slow speed, and/or when blipping throttle on deceleration downshifting. Have observed light white, almost blueish smoke back thru intake on an occasional cough. The thundermax module has been diagnosed, replaced and the zipper tech's are pretty confident it's not the module, therein lies the problem. It acts like a fuel problem, Harley says it's the tuner, Zippers says it's sounds mechanical, I personally think it's also mechanical. Wet Sumping? The bike also seems to labor much more at cruise, hesitation is also evident and it's substantially louder.
Best description: is an out of tune bike with retarded timing that coughs back thru the intake

this is an 08 street glide w/ 9,000 miles, a thundermax w/ auto tune, screamin eagle air and rinehart true duals.

appreciate any thoughts, suggestions, advice.

 

Put the stock ECM back in and see if its any better...It will tell you which one is the problem !

 

Sound like fuel stavation.
Scott

 

Tried running stock ECM and couldn't make the bike cough, thought I was done and ready to send back the Thundermax. Then I thought (first mistake) to check the 02 sensors, well, the front cylinder was sooty black, the rear cylinder was chalky white....Hmmm. talked again with Zippers, now there really stumped.
I went as far as to replace the front exhaust gasket just to be sure, and re-installed the thundermax, right back to coughing through the intake.

What could be making that front cylinder sensor think it's lean, all the intake seals, gaskets and o-rings have been replaced prior to this, so there is no intake leak.

again, any opinions would be welcomed... Thanks so far

 

Just a dumb question or two intryign to help: Did you allow the bike to warm up at install of the Thundermax, or have you done anything in error like re-loading a map, and the process gets interrupted? Also, do you for sure have the front 02 sensor in the front pipe and the rear in the rear pipe? Can't think of anything else, was thinking fuel pump or filter in the tank, but with the stock ecm running the bike, that almost answers that one right off the bat..... And the connection of the main harness is good and tight, no bent pins, and some dielectric grease is there?