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Discussion Starter #1
Alright here goes nothing. Probably a simple question. I just finished stage 1. I took my bike to get rejetted. It is running great but the only problem is once in a while at idle, if I sharply roll the throttle (like when rev matching for a downshift) it backfires. What is this? Too lean or too rich? Idle jet or what?


06 Sportster 883 Custom, straight pipes, semi apes, saddlebags, sissy bar
 

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Too lean. My bike does the same thing sometimes after I missed the pipes more. Really need to get a little more fuel into it. They turning the AF mixture screw under the carb out more. The max you can go is around 3 turns or it could fall out. Keep that in mind. Worst case you buy a new pilot jet for it no biggie.

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Discussion Starter #4
Alright thanks guys that's all I needed!


06 Sportster 883 Custom, straight pipes, semi apes, saddlebags, sissy bar
 

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Been dealing with the same issue on my FXD I recently purchased. The guy I bought it from is an admitted "tinkerer" and we have been fixing his work since day one. Im still trying to work out the kinks in the carb and have gone both ways i.e. Lean to Rich and still get the back fire altho better then day one. Leason be wear of Tinkerers selling harleys when they admit they prefer Brit motors
 

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Discussion Starter #6
Well hopefully mine can be corrected. It never used to. I remember reading somewhere what it meant if it takes a few seconds for the idle to drop back down to normal. Like when I release the throttle it slowly drops instead of just going straight down. Anyone hear of this? Does it mean I have an exhaust leak at the head? Or an intake leak?


06 Sportster 883 Custom, straight pipes, semi apes, saddlebags, sissy bar
 

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After making sure the cables are free and lubed, clean the carburetor. The needle could be sticking up. You started talking about a backfire, and now you're talking about idle down issues!! Both are carburetor related, but most likely not the same thing.
 

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Discussion Starter #8
Well it was like this when I got it back from the shop. I didn't have the necessary carb support bracket when i did the stage one. It is coming today and I will put it on. The guy told me to put the bracket on and ride it and let him know how it is. He said he may have to put in one size bigger pilot jet. The idle thing I agree is something different. I don't think it's the cable. And the jets are brand new so I don't think they're sticking...


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What size jetting currently?
 

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The biggest problem you have is with the straight pipes. Some out there claim to be able to tune them. I don't believe it.

If you are going to run the straight pipes, be prepared to have little ticks like you are seeing. No manner of rejetting it is going to make much of a difference, you will always have some burp or cough or weird performance tick. Spent a good deal of time and effort trying to dial in my cycle shack drag pipes, it just can't be done.

You need some pipes that have some back pressure to be able to properly tune the engine.
 

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Discussion Starter #12
Sorry. My sig says I have straight pipes. I changed it on the online site but for some reason it keeps coming up in the iPhone app. Here is the series of events. I had straight pipes. Bike was running lean. It was spitting out the carb in low rpms. I ditched the straight pipes for screamin eagle shotguns. Bike was running a little better with the added back pressure. Then I put a stage 1 air intake on. Bike ran awful spitting and coughing and carrying on. I could barely limp to my bike shop for the rejet. After the rejet the bike ran great no coughs or spitting whatsoever. He told me to let him know how it was he said he might have to go up one more size on the pilot. It was fine on the first ride, but once when I took it for a longer ride and got it real hot I noticed (mostly sitting at a light when it turns green) I bump the throttle quick and it backfires. So I think I'm going to bring it back for one size bigger pilot jet. I believe the slow idle drop is another issue.


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Ok, sounds like it is just a little too lean. Maybe the tech went up a size and still had to turn out >2-1/2 rotations to get it where he wanted it to be. I upped my jet from 45 to 48 and am running about 2 turns on the adjuster. Some folks do run a 50 jet. Some talk about shimming the needle.

It would be easy to check the adjustment for yourself. Just get a long thin screw driver and turn the adjusting screw clockwise until it seats, be sure to count the number of turns you need to seat it. If it is more than 2-1/2 turns, you want to go up another size on your jet. If it is less than 2 turns, back it out the number of turns you counted and add another 1/4 turn. Then see how she runs.
 

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Discussion Starter #14
Yeah that's the plan for that issue. Thanks man. Now I'm still wondering about the slow idle drop...that's annoying. I come to a light and it sounds like my idles way too high. Then it slowly drops back down. It sounds like my old 94 Chevy on a cold morning.


06 Sportster 883 Custom, straight pipes, semi apes, saddlebags, sissy bar
 

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Haven't had that problem, but I understand it can be caused by a lean fuel condition as well. Wait and see how it runs after adjustment.
 
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