Performance mod overlooked....exhaust gasket!
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Joined: Dec 2012
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From: California
Performance mod overlooked....exhaust gasket!
I recently did a big bore, FMoto head install and wanted to get away from the factory fiber crush type exhaust gasket. I first tried the smaller SE ring crush type without success due to leakage. Wasn't aware of any other type so I went back the to larger OEM fiber crush type for that good seal. After a week of new motor break-in, I decided to take a look at the exhaust port to see if there was any restriction from this crush type gasket. Holy crap was I surprised to find THIS much crush effect obstructing the exhaust port! As you can see, the black area was restricting the port! I haven't seen or heard much about this topic so I did some research and found the perfect solution as you can see. A set of Copper Compression Rings from 'James Gaskets' for a messily $12 bucks! Tip? I used a little anti-seize on the ring to hold in place until pipe install. The copper ring will not crush into the port however, it isn't a 'press fit' (very close though) on the outer wall either. Great seal and more power!!
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Joined: Nov 2012
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From: Fla
He probably meant...
Compressed fit, meaning the gasket is compressed when the exhaust flange is tightened down...
A 'pressed fit' would mean that the part is pressed into place with some force using any number of different means. Like with a shop press, an arbor press, or just a nuts/bolts/washer press to use in place on the engine or part...
That copper ring reminds me of the copper washers used on the old british bikes. We would re-use them by re-annealing the copper. You'll be better off using new copper gaskets when disassembled again, but if you're interested here's a site that explains how to re-anneal copper washers/gaskets...
http://www.motoiq.com/magazine_artic...r-washers.aspx
After looking at the Genuine James gasket site, I found that the copper exhaust gasket is actually a crush washer. So I don't believe re-annealing is an option, since it may actually be hollow to allow the copper to conform in the space and present a better seal. Good read anyway, and very short, if you are interested...
BTW, that was a good catch ironjunkie! Restricting a port can defeat the purpose. Good tip for anyone, modified engine or not...
Compressed fit, meaning the gasket is compressed when the exhaust flange is tightened down...
A 'pressed fit' would mean that the part is pressed into place with some force using any number of different means. Like with a shop press, an arbor press, or just a nuts/bolts/washer press to use in place on the engine or part...
That copper ring reminds me of the copper washers used on the old british bikes. We would re-use them by re-annealing the copper. You'll be better off using new copper gaskets when disassembled again, but if you're interested here's a site that explains how to re-anneal copper washers/gaskets...
http://www.motoiq.com/magazine_artic...r-washers.aspx
After looking at the Genuine James gasket site, I found that the copper exhaust gasket is actually a crush washer. So I don't believe re-annealing is an option, since it may actually be hollow to allow the copper to conform in the space and present a better seal. Good read anyway, and very short, if you are interested...
BTW, that was a good catch ironjunkie! Restricting a port can defeat the purpose. Good tip for anyone, modified engine or not...
Last edited by Def Mute; Mar 4, 2013 at 11:04 AM.
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Joined: Jul 2008
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From: Indian Land, SC
Question, did you torque the flange nuts to HD specs?
Reason being, I installed some MGS Duals on my bike, torqued to specs, 2 heat cycles and re-torqued to specs. I had to remove the rear pipe and the HD stock gasket had not mushroomed out into the exhaust port.
The James Gasket's was a good find though and I will book mark for the future.
Reason being, I installed some MGS Duals on my bike, torqued to specs, 2 heat cycles and re-torqued to specs. I had to remove the rear pipe and the HD stock gasket had not mushroomed out into the exhaust port.
The James Gasket's was a good find though and I will book mark for the future.
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Joined: Dec 2012
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From: California
Torque- No torquing, just tight. The exhaust flange appears to be flush with the head.
Fit- The ring didn't fit tight to the outer wall of the port, requiring anti-seize to hold it in place until I got the pipe in place.
ID- The used fiber gasket measured 1 1/2" after crushing. I'm certain the copper ring will not crush into the port like that, if any. Hope this info helps!
Fit- The ring didn't fit tight to the outer wall of the port, requiring anti-seize to hold it in place until I got the pipe in place.
ID- The used fiber gasket measured 1 1/2" after crushing. I'm certain the copper ring will not crush into the port like that, if any. Hope this info helps!
Elite HDF Member
Joined: Jul 2008
Posts: 4,741
Likes: 45
From: Indian Land, SC
Torque- No torquing, just tight. The exhaust flange appears to be flush with the head.
Fit- The ring didn't fit tight to the outer wall of the port, requiring anti-seize to hold it in place until I got the pipe in place.
ID- The used fiber gasket measured 1 1/2" after crushing. I'm certain the copper ring will not crush into the port like that, if any. Hope this info helps!
Fit- The ring didn't fit tight to the outer wall of the port, requiring anti-seize to hold it in place until I got the pipe in place.
ID- The used fiber gasket measured 1 1/2" after crushing. I'm certain the copper ring will not crush into the port like that, if any. Hope this info helps!
Those copper washers do look interesting. What site did you buy them from? Link maybe?
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Outstanding HDF Member
Joined: Jun 2012
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From: Atlanta, Georgia
WOW!!! Your 107 build must be a monster motor in order for that small amount of restriction to cause a decrease in performance!! They must have used the "special" b-heads and the "custom race proven" big bore kit instead of the regular heads and regular big bore on your bike. Just sayin...
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Joined: Dec 2007
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From: Bay Area
I have replaced dozens of sets of pipes and never had an issue with oem gaskets, Ive even reused the same ones a couple of times. I would venture to say it was an installation issue that caused it to fail, especially since you didnt use the book spec to torque the nuts.
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