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Old 05-25-2004, 04:08 PM   #1 (permalink)
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Backfiring - Popping out exhaust

My '99 FXR3 is backfiring HORRIBLY out the exhaust when it is cold...and even when it should be warmed up. Here is what I mean. When I 1st start my bike ('99 FXR3 80" EVO) it idles fine. I let it warm up for a good 5-6 minutes (1 cigarette's worth of time) before I pull off. This morning it warmed up for probably longer because I had to put the dogs up and stuff...anyways...I'll continue.
When I give it some gas it sputters, spits, pops, and backfires like crazy. Not a single pop every now and then...I mean CONSTANT backfiring out the exhaust. I can't ride it. I rode about a mile like this hoping it would clear up once it warmed up...but it didn't and I had to go back home and get the car.

Does this sound electrical? Could it just be the air/fuel mixture screw needs adjusting? Maybe an air leak at the intake?

Help is appreciated!! All I know is that kids in the ghetto 10 miles away are ducking for cover when I ride my FXR thinking there is an AK-47 popping off some rounds nearby.

Thanks,

Kent
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Old 05-25-2004, 04:54 PM   #2 (permalink)
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I'm as ignernt as they come, but my overly rich bike likes to do that to me when the plugs finally get too fouled to fire. I'll start losing one cylinder intermittently, then it all goes to hell. A friend has convinced me that the only way to correct an overly rich carb is to load in a bigger cam. Like I said, I'm ignernt.

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Old 05-25-2004, 05:06 PM   #3 (permalink)
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Well...I just bought new plugs and gapped them per HD specs. I bought these plugs just a month or so ago and have only ridden 2 or 3 times with them.

I tried a hotter plug at 1st...but it backfired REALLY bad when I did that...then I put in the new cooler plugs (as were in there already) and it quit backfiring...now it is backfiring again.

I'll check my plugs. I don't want to do a freaking cam change right now.
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Old 05-25-2004, 05:07 PM   #4 (permalink)
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[QUOTE= A friend has convinced me that the only way to correct an overly rich carb is to load in a bigger cam.
bigger cam for an overly rich carb???? change the jets maybe??
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Old 05-25-2004, 10:59 PM   #5 (permalink)
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Uhh...don't let your friend work on your bike anymore, lol. Changing cams to lean out a carb is like "fixing" a stretched chain by getting a bigger sprocket. Just a shot in the dark here, but...2 quick questions...

1. Do you by chance have aftermarket pipes? or...(wince) stock pipes that someone has "drilled out" the baffles to make them louder?

2. has any other mod-type work been done to the bike - airbox "gutted", etc...?
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Old 05-26-2004, 06:51 AM   #6 (permalink)
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My 91 heritage used to do that. If the plugs get fouled during warm up it will run like sh!t. All I did was use the choke less. Instead of letting it warm up with the choke on, I would let it run about 30 seconds with the choke on push the choke in and use the throttle with tension wheel on to complete the warm up. Don't know if you problem could be this simple.
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Old 05-26-2004, 07:41 AM   #7 (permalink)
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[QUOTE=choppers4life][QUOTE= A friend has convinced me that the only way to correct an overly rich carb is to load in a bigger cam.
bigger cam for an overly rich carb???? change the jets maybe??[/QUOTE]

That was a joke...sort of. Of course I could just rejet. But I'm ready to spend for some more power so I'll just tolerate it until I do the upgrade then rejet for the new combination. It's not so rich to be real annoying, it just fouls plugs about every other oil change. It still runs pretty good.

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Old 05-26-2004, 08:50 AM   #8 (permalink)
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There are other mods to the bike, but it has been like this since I bought it.

The '99 FXR3 came with the Screamin Eagle air cleaner setup - still installed
It had Vance & Hines shorties...which I hated and changed to Hooker Longshots - neither had baffles.

I have made NO changes in accessories or anything this year at all. This just started happening a little about a month or 2 ago. It started just before I noticed my rocker box leaking oil everywhere, so I'm convinced it has something to do with oil getting in the seals/gaskets at the intake and causing an air leak.

I'll be taking the carb off tonight to investigate and replace the gaskets/seals in there.
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Old 05-26-2004, 09:08 AM   #9 (permalink)
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Check for intake leak my 99 FLSTF done the same thing both intake gaskest were washed out replaced tham no more problem. Just spray some WD40 around the intake where it bolts up to the head if you notice any change in the idle the gaskets are washed. Consider buying new flanges for the intake at the same time (cheap insurance).
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Old 05-26-2004, 10:05 AM   #10 (permalink)
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agree with that last one. sometimes the intake flanges warp also. ran into a guy with a similar concern last year. that took care of it.
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Old 05-26-2004, 11:25 AM   #11 (permalink)
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Quote:
Originally Posted by Chilly
That was a joke...sort of. Of course I could just rejet. But I'm ready to spend for some more power so I'll just tolerate it until I do the upgrade then rejet for the new combination. It's not so rich to be real annoying, it just fouls plugs about every other oil change. It still runs pretty good.

Chilly

Ahhh...my apologies...got it now.
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Old 05-27-2004, 03:48 PM   #12 (permalink)
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Just a thought your manuel has a test for the VOES I've found your problem on other bikes with a bad switch and replaced it and no more problems

Good luck
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Old 05-28-2004, 08:56 AM   #13 (permalink)
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Well...it was NOT the intake gaskets. I replaced them, but the old ones looked perfect. No change...still backfires HORRIBLY. This sucks. I took the carb up to my buddy that is going to clean it all up for me. There was a lot of oil residue in the carb and all over it from the rocker box spitting oil all over everything.

Today after work I'm going to check the Petcock screen and put the carb back on. I don't know what is causing this.

Also...found out the carb has a Thunderjet kit installed on it.

I don't know crap about VOES. Can anyone tell me what FLHTP is talking about? What test?
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Old 05-28-2004, 09:02 AM   #14 (permalink)
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check the timing could be to late which will cause it to backfire.
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Old 05-28-2004, 12:08 PM   #15 (permalink)
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Just a thought here, I had some serious problems with backfiring through the tailpipe and I mean shooting about a 3 inch blue and white flame out the back end. There was a short from the rear coil terminal and the wire. Caused all kinds of stuff to happen including the backfiring.

Once this was fixed and the carb retuned it cleared all backfiring up.

Just my 2!
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