Yellowing of exhaust pipe cobras - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 17 (permalink) Old 06-27-2013, 05:38 AM Thread Starter
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Yellowing of exhaust pipe cobras

The bike I just got already had cobra exhaust installed. The left pipe( the one that runs under the bike to the other side) is very yellowed / brassy looking where it first comes off the cylinder. I'm sure these are a dumb string of questions but is this caused by excessive heat? Is this different than bluing? Does it mean the cylinder is running too rich/ lean?

Thanks for answering my newbie questions. Been reading the verses but some things I just don't get!
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post #2 of 17 (permalink) Old 06-27-2013, 09:22 AM
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I believe that's from running too rich, blue/lean. If you ever decide to sell those I've been searching for them for a while.


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post #3 of 17 (permalink) Old 06-27-2013, 09:27 AM
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Originally Posted by Hermis View Post
The bike I just got already had cobra exhaust installed. The left pipe( the one that runs under the bike to the other side) is very yellowed / brassy looking where it first comes off the cylinder. I'm sure these are a dumb string of questions but is this caused by excessive heat? Is this different than bluing? Does it mean the cylinder is running too rich/ lean?

Thanks for answering my newbie questions. Been reading the verses but some things I just don't get!
Questions can be answered here, use of the "Search" button can produce many many answers and educate you beyond on most subjects, allowing FEWER questions.

Using the search button I got an education on colored pipes.

hope this helps
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post #4 of 17 (permalink) Old 06-27-2013, 02:14 PM Thread Starter
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Questions can be answered here, use of the "Search" button can produce many many answers and educate you beyond on most subjects, allowing FEWER questions.

Using the search button I got an education on colored pipes.

hope this helps
Thanks for heads up. I searched for hours before I made this post. Found a ton of stuff on bluing, and mentioning of yellowing. In the posts where yellow was mentioned, no reason was given. After searching more, my understanding is that yellowing is the same as bluing or at least the same process, and the pipes turn yellow before blue? If that is the case I know what to do!
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post #5 of 17 (permalink) Old 06-27-2013, 02:16 PM Thread Starter
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I will let you know... They are a bit loud for my taste but I think that project will come down the road a ways!
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post #6 of 17 (permalink) Old 06-27-2013, 02:29 PM
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Quote:
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Thanks for heads up. I searched for hours before I made this post. Found a ton of stuff on bluing, and mentioning of yellowing. In the posts where yellow was mentioned, no reason was given. After searching more, my understanding is that yellowing is the same as bluing or at least the same process, and the pipes turn yellow before blue? If that is the case I know what to do!
Yellow does not mean they will turn blue, but if lean enough they will. Most go overboard, but it means it is probably lean at cruise. At steady mph cruise, does it 'hunt'? Require small throttle input to hold steady mph? Cruise is the pilot circuit, OEM intentionally sets this lean. Post your setup?
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post #7 of 17 (permalink) Old 06-27-2013, 02:36 PM
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Definitely from being lean, rich only makes them black on the inside but never a change on the outside.

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post #8 of 17 (permalink) Old 06-27-2013, 03:38 PM Thread Starter
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Yellow does not mean they will turn blue, but if lean enough they will. Most go overboard, but it means it is probably lean at cruise. At steady mph cruise, does it 'hunt'? Require small throttle input to hold steady mph? Cruise is the pilot circuit, OEM intentionally sets this lean. Post your setup?
It doesn't hunt at cruise, holds real nice. I'd like to post my setup as soon as figure out what it all is! I got this bike with a lot of aftermarket custom work done by the previous previous owner. I know it has cobra exhaust. Carbs screws haven't been adjusted as far as I can tell since the caps are still there. Got the mf battery in and marbling (im getting a lot of popping on decel) it this weekend along with changing to iridium plugs. Ill get my setup into my signature once I know what's all there!
Thanks,
Hermis
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post #9 of 17 (permalink) Old 06-27-2013, 06:14 PM
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Just as a side note, Blue Magic metal polish and a polish ball on a drill works wonders on that yellowing.( ask me how I know that )

http://www.amazon.com/BlueMagic-400-...rds=blue+magic

and

http://www.amazon.com/Extra-Thick-La...s=buffer+drill
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post #10 of 17 (permalink) Old 06-27-2013, 06:15 PM
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When I got my Bonneville the first thing they told me was "the headers will blue on you, it's normal"
They are blue the first half foot, the rest goes from a dark wheat to a lighter yellow as you move from the cylinder.

This is caused by heat. The rear cylnder on the Vulcan gets hotter than the front. Yes, it's due to a lean mixture, but is not an indication you're running "dangerously" lean. Check your plugs that's how you tell.

There are things on the market you can polish the pipe with that might get rid of the yellowing, but unless you change the jetting it will just come back.

As long as the plugs look good I wouldn't worry, but you can try installing a bigger main jet.
(As you got the bike used, I have no idea if the other owner changed the jetting. But I think even stock bikes use a larger jet in the back)

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