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Discussion Starter #1
So the bike I bought has some performance goodies thrown on by a PO, and backfires a ton on decel. I thought maybe it was all that damn ethanol they throw in our gas these days, but paying the extra cash for the old fashioned gas didn't seem to fix it. Then I thought maybe I need to block off the Reed valves; turns out that's been done too. Adjusting the cobra fuel controller (F2000i) didn't fix it, but sure did hurt my fuel economy. Then I read that exhaust leaks cause it too because they allow oxygen to enter the exhaust to mix with any unburnt fuel.

So then I started looking real close at the exhaust where it comes out of the cylinders, and I noticed this blackening right where the pipe connects to the rear cylinder. Am I seeing what I think I'm seeing here? If so, I reckon I'll need to pull it off and replace the crush gasket...should I just replace both while I'm at it or just leave well enough alone on the front cylinder?
 

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Seems like maybe the PO reused the old gaskets. Personally, I'd do both. That way I'm sure it's done right. Plus if the backfiring persists after the gasket change, you know to search elsewhere for the cause. Mine pops as well. I picked up a set of the hardley gaskets. Just need to find time to fix it. Here's the how to with two hardley gaskets.

https://gadgetsfixitpage.com/article.php/banish-exhaust-leaks
 

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Looks like an exhaust leak to me. I've heard of some aftermarket exhaust headers cracking the weld at the header flange, in addition to the flange bolts loosening up as the gasket is flattened/reused because the header acorn nuts bottom out before getting tight. Hardened washers under the acorn nuts will make the nuts more effective.

Oh, and pet peeve. Its not back-firing, just popping in the exhaust on closed throttle decel. True back-firing is the fuel/air mix spitting back wards out the intake. An exhaust leak at the header flange will cause popping in the exhaust.
 

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Discussion Starter #5
Looks like an exhaust leak to me. I've heard of some aftermarket exhaust headers cracking the weld at the header flange, in addition to the flange bolts loosening up as the gasket is flattened/reused because the header acorn nuts bottom out before getting tight. Hardened washers under the acorn nuts will make the nuts more effective.

Oh, and pet peeve. Its not back-firing, just popping in the exhaust on closed throttle decel. True back-firing is the fuel/air mix spitting back wards out the intake. An exhaust leak at the header flange will cause popping in the exhaust.
Haha yes, I've learned the difference between backfiring and popping in the time between posting this and now. Replacement gaskets had to be order through the dealership and just arrived yesterday, so I'll be replacing them this week.

Good idea on the washers under the acorn nut, I'll toss one under there just to be sure its all kosher.
 

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Discussion Starter #6
Silly question perhaps, but bear with me.

I've heard it's a pain to get the gaskets to stay in place while positioning the pipes. I've also heard a dab of grease will help hold it there. However, I don't have any grease sitting around...but I do have a tube of RTV.

So my question is, would a dab of RTV do any harm just to hold the gaskets in place in lieu of grease?
 

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Silly question perhaps, but bear with me.

I've heard it's a pain to get the gaskets to stay in place while positioning the pipes. I've also heard a dab of grease will help hold it there. However, I don't have any grease sitting around...but I do have a tube of RTV.

So my question is, would a dab of RTV do any harm just to hold the gaskets in place in lieu of grease?


Use high temp silicone(copper), a dab on the seating surface will keep the gaskets in place until the flange is tight


Saddle up and feel the wind in your Helmet! ATGATT
 

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Discussion Starter #8
Small update:

Got the exhaust pulled off, and the crush gaskets aren't the only issue here (in fact, they looked fine). The flanges are warped pretty bad and the retaining ring on the rear cylinder is just totally mangled. They also aren't the OEM flanges, as I've learned. I'm not sure why the PO didn't use the stock parts (perhaps because they're so expensive, to the tune of $140 for a full set thru the dealership, versus $30 on Amazon for style he used).

I found the OEM parts on partzilla for $17.10/ea (OEM is 2/pipe...odd design if you ask me), so it cost me about $90 after tax and shipping. So now my bike is confined to the garage, exhaustless and sad until they show up, hopefully next week.
 

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Someone has installed the HD style exhaust flange, and as you have found out, it won't work. Should have asked, I have a set of factory flanges I would have let you have at a good price.

 

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Discussion Starter #10
Someone has installed the HD style exhaust flange, and as you have found out, it won't work. Should have asked, I have a set of factory flanges I would have let you have at a good price.

Order hasn't shipped yet, can cancel still. What are you thinking?
 

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Discussion Starter #19
USPS took their sweet time delivering them, but they showed up today, and I installed them today. Still pops, but not near as often and not near as loud. So I'd call it a success!

Thanks again man.
 
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