Well I got my 97 Fatboy back from an Indy yesterday and they installed new Vanes and Hines Longshots. The sound is awesome and they look great. I had longshots before but they were only 1 3/4 in and did not have heat shields on them. The new ones are 2 1/2 in with heat shields. The sound with these is a more full sound Potato Potato!!!

She backfires on decel which I had as a problem with the old pipes. With the new pipes I am also having backfiring as I shift up in gears. It is when I let off on the throttle and then shift.

The bike wants to run and is more peppy than the other pipes. I am going on vacation this week so I do not want to bring it back to the indy to have them look at it. A friend of mine says that I may need to have my carb tuned to the new pipes. Any thoughts here would be helpful. I would really like to eliminate the backfiring all together. As a side note, I will probably take the bike to the Stealership this time to do the work.

 

Sounds like a leak or ecm problem

 

Check where the new pipes attach at the heads. Makes sure gaskets are the right ones and that they are tightened equally.

 

+1 on the leak. I had mine doing the same thing a little backfire on decel, started it the other day, and felt air coming out by the muffler clamp. Moved into proper postion and tightened it and walla, no more backfiring.

 

Thanks for you comments. I will give it a try.

 

have a BSL on my bike, K&N filter and PCIII/dyno'd and have decel pop. No exhaust leaks and per my local indy, no further tuning can get rid of it.

 

You do have to have the carb rejetted. I had a friend who had longshots and every time you let off the throttle it sounded like glasspacks on a car, even when you upshift, personally I didnt like the sound compared to my V&H staggered duals on my 99 fatboy.
The jetting accounts for the backfire, but the decel rumbling if that is bothering you too, may be due to the larger 2-1/2" pipes, you may consider exhaust cones or a quieter baffle. Not sure what pipes you had before but with louder pipes the decel popping is more noticable than the quiet pipes.

 

Took it out for a ride this morning. With the choke half way out and the rpms up it did not backfire when I shifted. Once it was warmed up and the choke was pushed in all the way, the backfiring began again while up shifting. Sounds like it is both cyclinders as I hear a pop pop.

The older pipes are the ones in my avatar picture and were 1 3/4 in. I was the second owner and do not know who made the them. I also had the decel backfiring with the previous pipes generally in 3rd gear.

Both the new and old pipes are pretty loud.