Question RE: Craigslist '80 GS750 with blue/purple headers...possible exhaust issue?w

[FLsailor]

Hey everyone,

First of all, I'm a brand new member (first official post) so thank you in advance for dealing with me, haha. I also apologize if I've placed this thread in the wrong sub-forum. Please let me know if I need to move it.

I'm a 6-month motorcycle "veteran," and have voraciously ate up every bit of bike-related knowledge I could find since getting my license in August.


I've found a 1980 GS750E on my local Craigslist which I'm very interested in purchasing.

Pictures from two separate CL postings available HERE and HERE.

After talking on the phone with the seller, he has seemed to indicate recent engine work involving "replacing rubber and seals, carb clean, etc." as well as replacing the original air intake box as the bike "wasn't able to rev above 3k RPM or so." After since replacing the air intake, the bike functions normally, according to the seller.

So here is my question:

As you can obviously see from the Craigslist pictures, the headers are all kinds of blue and purple and gold.

Now, I understand that some discoloration is perfectly normal, especially for chrome plated and steel exhaust, due to heavy heat transfer.

But do any of you think the blueing on these header pipes are due to an incorrect air/fuel ratio? From what I've read, a too-lean mixture can cause over heating in the engine, and blue pipes can be a symptom of that.

Is there a way to be able to tell if the engine has suffered any damage (without the obvious answer of taking it to a mechanic!)

Is the discoloration rust? Is this something I need to even be worrying about in the first place?

Thank you so much in advance for any help you can offer.

All the best,
Nate

[Agemax]

as he has just rebuilt the carbs and fitted an airbox it sounds like he was running pod filters before and could not get it to run right. it was probably running too lean which would cause the headers to blue.
if it is running fine now then the bluing is not a problem and can be removed quite successfully.
welcome to the site by the way........

[Vmass]

Hey Nate,

I'm certainly no expert, but those pipes look very typical to me nd the rest of the bike looks pretty good too.

[sedelen]

4 into 1 headers have more of a tendancy to blue over stock pipes headers. Those headers really don't look that bad to me. I've seen way worse. But it does sound like he did, or maybe even still does have some issues with the carb jetting. Trial and error to get them just right when rejetting for headers and pods. A test ride and pulling the plugs and looking at them should help determine if it's close to being correct.
The headers can be de-blued and polished, you may have more problems dealing with the rust, if that is indeed rust though.

[Gregory]

4 into 1 headers have more of a tendancy to blue over stock pipes headers. Those headers really don't look that bad to me. I've seen way worse. But it does sound like he did, or maybe even still does have some issues with the carb jetting. Trial and error to get them just right when rejetting for headers and pods. A test ride and pulling the plugs and looking at them should help determine if it's close to being correct.
The headers can be de-blued and polished, you may have more problems dealing with the rust, if that is indeed rust though.

Where are the threads located on how to de-blue the pipes? Mine are way worse than the ones in his pictures.

[sedelen]

Where are the threads located on how to de-blue the pipes? Mine are way worse than the ones in his pictures.

Check this out, but read the whole thread.

http://www.thegsresources.com/_forum/showthread.php?t=203625&page=3

[tkent02]

Check the compression before you buy it. If there were any burnt valves it would show up on a compression check. They are a bit blue, but not much. I would guess that it's fine, but needs a little jetting change or at least some carburetor adjustments.

Like others have said, 4-1 pipes tend to blue more than factory exhausts as they are single wall. We have all seen way worse bluing with no engine damage.

[FLsailor]

Thank you again everyone for such a quick response with my post! I appreciate how informative and welcoming the members on here have been.

This is another newbie question (and I've been trying to search the forums for related info): When I go and check out this bike in person, aside from the standard "used motorcycle inspection procedure," what specifically should I look for in addressing the blueing / possible ratio problem issue?

According to you guys, I should check the compression, the spark plugs, and the power on a test ride. Anything else?

Again, thank you to everyone. You've all been really helpful.

[tkent02]

Just leave your "I wanna buy it" self at home. Go add up all of the little costs it will need, tires, chains, cables, routine maintenance things. Look for signs of a hard life. Crash damage. Rust and corrosion makes everything you will do to it a pain in the butt. Look for clean oil and brake fluid. Leaky forks, other leaks. None of these things are a deal breaker, but they should effect what you offer for it. Be aware that is about the only model GS who's engine isn't always considered bulletproof. Some last a long time, others have oiling issues.

Overall that bike looks nice up up close in person you will spot more deficiencies.

Post up a location, perhaps one of us more experienced bike buyers will go along to look at it with you.

[mrbill5491]

Yup, bluing on those pipes isn't bad, mine are far worse. Though I kind of like the bluing, gives it some character no?

[SqDancerLynn1]

I would check the exhaust cam if possible ? The second gen 750 80-82 had oiling problems if not taken car of

[BassCliff]

Greetings and Salutations!!

Hi Mr. FLsailor,

If that's the one you're going to take home then this information should come in handy. It's you're S.W.A.G.

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Thank you for your indulgence,

BassCliff