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Author Topic: Back fires and surges at low rpm  (Read 12684 times)

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crunch29

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    • CVO1: 2010 seultra, red and black, D&D fat cat,SE Ventilator air cleaner, se pro tuner,Pro 110 performance upgrade
Re: Back fires and surges at low rpm
« Reply #15 on: May 02, 2010, 07:30:46 PM »

Just to clear things up. I didn't download a map from Steve. I purchased all my parts through my local dealer and they dyno tuned the bike. The reason I did this was because they wouldn't warranty my bike if I had someone else install parts and map my bike. I'll post my tune and I think the dip in my low rpms is what I'm feeling. Also I did contact D&D because I am running the performance baffle which is pretty much open and doesn't have much restriction. I think I read in a post a while ago this was someones problem. Anyhow D&D said the performance baffle should work fine on my bike, they thought it was the tune.

''

Keith
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grc

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Re: Back fires and surges at low rpm
« Reply #16 on: May 02, 2010, 07:43:44 PM »


All I can say is, if the engine shouldn't be run at 1500 rpm then Harley needs to reset the idle speed to 2000 rpm and make the whole point moot.

One earlier comment indicated that even with a "perfect tune" the writer couldn't run his bike at 1500 rpm in 2nd gear.  The engine is designed to run between approximately 900 and 6000 rpm, and if it is tuned properly it will run at any point between those two extremes without surging, backfiring, spitting, coughing, puking, or any other -ing.  If it won't, then you don't have a "perfect" tune, period. 

I can run my bike at 1600 rpm in 4th gear without bucking, jerking, backfiring, etc., so I find it a little ridiculous that someone can't do the same in 2nd gear.  And I can smoothly accelerate (very light throttle) in 2nd or even 3rd from that engine speed with no problems.  I don't grab a handful at those engine speeds, but if I did it wouldn't be an excuse for the engine management system to create backfires, hesitation, surging, or any of the other symptoms mentioned.  Telling someone with those problems to fix it by running around at 2500 rpm and up all the time is something I'm not surprised to hear from the typical Harley dealership, but it's not any more valid than when they tell you stuff like the oil from the air cleaner soaking your leg is normal.  They don't "all do that", and the ones that do need to be fixed, not just blown off with technically incorrect BS.

As previously noted, these are not engine speeds that we should use when putting a significant load on the engine, and I believe my first post made that point.  But there is absolutely no technically valid reason why a Harley engine shouldn't run smoothly without hiccups and backfires at all speeds from idle to redline.  Throwing in the "lugging" argument is just a way to avoid the real point and the real problem, which is the fact that the folks supposedly tuning the subject bike don't appear to have a clue.  What would the answer be if he reported misfires and surging at 5500 rpm, that he was revving it too high and needed to shift earlier?

Jerry
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Jerry - 2005 Cherry SEEG  -  Member # 1155

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Doc 1

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Re: Back fires and surges at low rpm
« Reply #17 on: May 02, 2010, 08:05:01 PM »

Thanks for the offer Doc... Ya can't change this old dog's habits so easily. HDA is about 1.5 hours away from me or I'd come say Hey.


Ahh..too bad, would have loved to see ya show up for lunch or something.
Doc
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