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Engine Stumbles, coughs, backfires

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Old 10-14-2011, 11:57 PM
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Default Engine Stumbles, coughs, backfires

I installed a Thundermax and the bike ran wonderfully for a month. Then all of a sudden it started running very lean. Literally ran great to a stop, then when I restarted the bike ran crappy.

The Thundermax seemed to try and add fuel as it got better but it would not go away. It being a stumble/cough/misfire at 30 mph and 2500 rpm's on up, very light throttle positions.

I put the stock ecm back on. Same problem. Bike runs fine at speed, but not idling around town, unless I lug it at 2000 rpm's....

Any ideas? Harley Dealership just says everything is crap and I need their version of a tuner. I already have the TTS and that map worked just fine...

Appreciate any ideas.
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Old 10-15-2011, 01:30 PM
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It's possible it could have nothing to do with the tuner. An intake leak will cause it to run lean and not run well. I replaced the intake seals twice on my Dyna and it finally runs like it should with the TMax. Also found a leak in the fuel line inside the tank and replaced that.
I would reinstall the TMax, load the correct map again, reinitialize according to Zipper's instructions and see if that makes a difference.
Of course the dealer will bash the tuner because they didn't sell it to you. Properly set up it should pull like a freight train.
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Old 10-17-2011, 12:19 AM
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This problem has been resolved. So, after hearing that my TTS map and the Thundermax were poor substitutes and that they would have to install Harley's tuner. Fortunately, they did not know how to flash the ECM so could not get their computer system to communicate with the bike's ecm. So they were encouraging me to send the ECM in to HD for flashing, buy this and that from them for close to 900 dollars.

I said thank you, paid 133 dollars for their fine diagnostic work and the wash job, and took my bike home. Since it was running just like a car would if it had plugged injectors, I bought a can of Redline injector cleaner that my Indy shop guy sold me, run it through the bike. Cost me another 6.00. Put it in the tank, added non ethanol fuel and rode home.

Reinstalled the Thundermax, reinitialized the Thundermax, and went for a 100 mile ride.

Results: Not one single misfire, or decel pop bike ran as smoothly as ever!

I was sure it was a poor connection somewhere since it started running cruddy all of a sudden. Well, I went through another "School of Hard Knocks" and found that I could solve the problem with a really simple solution.

Oh well...
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Old 10-17-2011, 06:36 PM
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Glad it worked out.
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