I just bought a new 05 ultra classic. had the Big Bore 95 kit put in it with 204 cams. Problem is now on deaccelleration when using the engine as a brake such as coming down an incline, the bike will pop and crack like a small backfire in the exhaust. The bike is fuel injected. I called my dealer and he said it was normal and that it was nothing to worry about. My friends have harleys and none of them do it. I also put Screaming Eagle mufflers on it. all the work was done before i picked the bike up. has anyone else had this problem ?

 

My bike does the same, especially when the engine is cold and the EFI is kicking in more fuel. I tried several different setups, but lost power or performance and went back to the original. You have to understand that the advanced timing requirements of a 204 is going to allow detonation in the exhaust, almost no matter how you set it up. The only cure, don't let up on the throttle.

 

My pprwk had a note on it to the effect that it's normal , after mine was installed on the 2000

 

Your new ECM download that was required for your Big Bore kit is flowing more fuel to the systems than before. Now that you have that increase in cubic inches and fuel flow the only part of the upgrade that did not get changed was the heads. The stock heads do not flow enough air for the increase in fuel, so it pass the excess fuel unburned to the exhaust. When you are decelling you are in essence creating a vacumn and the unburned fuel is igniting in the pipes. It is normal for most bikes that have that mod or any mod to the exhaust and breather systems to have that popping.

I have a 2004 Ultra Classic and I am running the Vance and Hines Oval Slip-Ons with the SE Stage I breather, stock ECM and a Power Commander III USB. It pops all the time on decell and I called dynojet about it and that was basically their answer. I think you are fine unless you are just plain bothered by it, but your bike is running fine.

I hope that helped a bit.

See you on the roads.....

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O-k guys I agree and disagree to some extent. If your running with the Harley ECM upgrade you are stuck with that program no matter what. What I mean is you can't adjust the fuel mixture at different rpm and load ranges. Now on the other hand with the Power Commander or other similar unit such as the Race Tuner, Daytona Twin Tec you can, which is just like jetting a carb. I really like the Power Commander and that's what I have run on more than one bike. I also really like the Twin Tec with the wego's but it is pricey, but if you can afford it is better than the Power Commander, because it actually reads the AFR off the exhaust and has a self tuning feature called BLM or Block Learn Mutiplier.

With the Power Commander you can manually adjust the low/mid/high load range of the engine to either a percentage richer or leaner in each of the ranges over the base map your bike is running. You can also fine tune even better in the software program, by selecting the cell ranges at a particular rpm and throttle percentage that you want to adjust leaner or richer of the base map. The best way is a dyno tune, but you have to find someone really good that just does'nt throw in a different base map or two and says it's tuned and takes your money.

It's all based on the AFR or air fuel ratio and you can get the decel backfire out even with the stock heads. If you look at the rpm that your bike is (if you have a tach) decel backfiring then you have an idea which cell ranges to start with. If you manually do it, it's just a matter of moving the bars up for richer or down for leaner and running the bike until you start to see improvement.

John TN

 

mine is stock, it did it with stock mufflers wasnt too bad but since yesterday, when i installed the rhinehardts, its pretty loud and ugly sounding.[:@]

 

I'm running Rineharts with Power Commander and Stage 1 upgrade. I have a very experienced Harley mech. that dyno'd mine and I get absolutly no back fire or popping. 2000 Screamin Eagle with EFI. Modified mapping (stock downloads are junk with any mods other than slip on SE2's).

This problem has been addressed many times on this forum with many different opinions. My take on it is if you're not happy with your Doctor-get a second opinion. Having a Dyno in your shop doesn't mean you know how to use it. There a lot of good shops out there but they have to be geared towards us crazy bikers that can't pass a shop without stopping for another go fast part.

Terry