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Discussion Starter #1
Hey everyone,

I ride an 08 Vulcan 900 custom and recently installed Cobra speedster shorts, Barons BAK, and fi2000r. I immediately noticed some popping on deceleration. Since then I have marbled the reed valves and tweaked my fi2000 settings which has reduced the popping a good bit. I know that I may not be able to completely eliminate popping, but I would like to have less than I do now.

The only other thing I can think of is a possible exhaust leak at the head pipe. I did use new crush gaskets when I installed the pipes. I have read where a lot of people say that Harley Davidson gaskets are thicker/better. Can anyone suggest any other ideas before I go through the trouble of re-seating the exhaust pipes? Also does anyone have the part # for the correct Harley gaskets that fit the VN900?

Any help would be much appreciated!
 

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i had the same issue with my new pipes........in a garage, get one of those long grill lighters and with the bike running, hold the flame around the pipes at the heads briefly - if the flame pulsates or goes out you have a leak. try loosening the nuts, wiggling the pipes then re-torquing them.
 

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Discussion Starter #3
i had the same issue with my new pipes........in a garage, get one of those long grill lighters and with the bike running, hold the flame around the pipes at the heads briefly - if the flame pulsates or goes out you have a leak. try loosening the nuts, wiggling the pipes then re-torquing them.
That's a good idea.. I'll give that a shot. I'm not sure if this is tied in to the same problem but I've also noticed that my bike seems to idle slightly higher after I've ridden it for a mile or two than it does before I ride it (this is of course after it idles down from choke).
 

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Using Your Marbles

You can use a couple of marbles to block the air injection hoses located at the very front of the front rocker cover and the very rear of the rear rocker cover to help reduce or even eliminate the "popping" heard on decelleration.

If you look from the right side of the bike you will see a hose coming out of the rocker at the locations described above. Remove the hose (held in place with a spring clamp) shove a regular marble up the hose far enough so you can clamp the hose back on the tube.

Doing this cuts off the air injection to help burn off unburnt fuel. If you do not do this you may get lots of poping on decel normally not heard because of the stock mufflers (though some of us here it even with stockers). Some with newer models (2008 and up) have said this did not work as well or possibly not at all on their bikes.
Quoted from VN2000.com
 

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How long into rides does it pop on decel? Mine popes within the first 10 minutes or so, but then it goes away.
 

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So far I haven't seen a VN900 that does not pop after adding new pipes. Are there any without this issue after installing new pipes?
 

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i have HK 2 into 1 Sideburner pipes and after marbling and fixing my leaks at the heads, i have no popping on decel.....will be soon installing a BAK and fi2000r, will let you guys know if it starts popping or not....
 

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i have a mod air filter and hard krome exaust and just installed new fi2000 and know my fuel injection light has come on and stays on how do i fix that or is it normal also what is the best setting for this bike at this setup
 

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So far I haven't seen a VN900 that does not pop after adding new pipes. Are there any without this issue after installing new pipes?
Nope after New pipes, marbling, and tighting all bolts and connections two or three times, and setting the fuel manager correctly the pop is almost none existence, almost, have a hard time making it pop when I want it to. Most open pipes will have some pop, the catalytic converter does a lot to deaden that on the stock pipes but even stock pipes will pop on occasion. And the old timer term is backfire, can be through the intake or pipes, still backfire. The pop is caused by the right fuel conditions in the pipe and the pipe is hot enough to ignite the mixture.

Saw one thread stating, if using Power Commander set the high rpm cells to 10 or above on zero throttle, and that will create a rich mix in the pipes that should prevent most backfire, unless running very hard and drop is sudden and total, seems to work good so far, but uses a little gas, so I have to decide if it is worth the price.

Ride Safe and keep the shiny bits in the air.
 

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I have a 2007 VN900 Custom. I installed an Arlen Ness Big Sucker, Power Commander, and knocked the screens out of the stock pipes. I like the sound and performance, but the popping everyone is talking about on this thread is driving me nuts. It happens at high rpms when I let off the throttle. I've tried both enriching and leaning the air to fuel ratio at 0 throttle and nothing seems to help. I haven't marbled it yet, because everyone seems to have a different opinion as to what is causing it. I would think that backfiring when letting off the throttle would mean its too rich at 0, but I can't seem to make it go away.

Does anyone, by some miracle, have a set up similar to mine that has solved this dilemma? And I hate to sound like a newb, but I'm getting ready to take a riding vacation and I'm wondering if this popping is damaging the engine.

Thanks for the help guys.
 

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I am the new owner of a 06 classic LT w/3500mi bone stock. I have noticed popping since I bought it and just figured it was normal. It really hasn't bothered me, I even think it sounds kind of cool sometimes. I HOPE it's not hurting anything or a sign of something seriously out of whack. I've heard people mention "marbleing" but haven't figured out what that is yet.
 

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Figgy, the hose coming out the top-back of the air box feeds fresh air in to the exhaust path. Pull the hose off the air box and stuff a marble or wire nut inside the hose.
 
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