Excessive header pipe bluing

My buddy has a 850 that just got a new Mikuni and a new exhaust system from Cdo Specialties. I noticed his new headers were ridiculously blue in a short period of time. I thought that maybe it was just running way too rich, but he said it was the cheap single walled pipes, and they all do that. I'm getting ready to finish putting mine back together, and don't want to trash my S.S. big bore exhaust. Is this normal or is my buddy missing something about tuning his Mikuni?

ALL the pipes are single wall, unless your talking Jap bikes. Pipes will blue, unless your running it at parade speeds.

Have him check that his auto advance/retard unit is advancing and retarding - when it should be. Needs a strobe timing light.

Running lean will also do that, doesn't have to be very lean to push the zorst temps up.

Can buy a polish thats supposed to take the blue out of blued exhausts - apparently works, to a degree - some chrome blues more than others. ??

Mikuni carbs are capable of being very lean or very rich with just one turn of the air screw, I turned my mates velo pipe a nice blue with just one turn of the pilot screw..the old amal's are less prone to weaken off the pilot mixture.
Mikuni pilot screw adjustment is tick over to 1/2-3/4 throttle and i noticed the adjustment is easly capable of making the header super hot!
To avoid blueing start rich, about 1 turn out..i went 2.1/2 and presto...BLUE..you can hear the engine note change with a 1/4 turn.

An excessively retarded ignition will push more heat out the exhaust.

As for protecting the pipes from blueing, you may want to look into ceramic coatings inside the pipe. I have read elsewhere that this protects them from blueing. If this is true then this is the time to do it, with new pipes and fresh clean steel inside surface.

Rohan said:

Have him check that his auto advance/retard unit is advancing and retarding - when it should be. Needs a strobe timing light.

Running lean will also do that, doesn't have to be very lean to push the zorst temps up.

Can buy a polish thats supposed to take the blue out of blued exhausts - apparently works, to a degree - some chrome blues more than others. ??

Click to expand...

From a bike mag, to prevent headers bluing, some manufactures double coat the chrome on the top part of the exhaust pipe ...............

One trick I use to minimize pipe discoloration is to get some very hi temp paint in a quart can and pour that down the head pipe. Block off each end and thoroughly coat the head pipe. In my experience that has prevented a lot of pipes from discoloring on my bikes, both Jap and Brit.

It may burn off but somehow it still keeps the pipes nice. I suppose if your carbs or timing were way the hell off they could still turn. Don't know as I've never had that problem.

Snorton74 said:

My buddy has a 850 that just got a new Mikuni and a new exhaust system from Cdo Specialties. I noticed his new headers were ridiculously blue in a short period of time. I thought that maybe it was just running way too rich, but he said it was the cheap single walled pipes, and they all do that. I'm getting ready to finish putting mine back together, and don't want to trash my S.S. big bore exhaust. Is this normal or is my buddy missing something about tuning his Mikuni?

Click to expand...

First off, I don't believe SS pipes will turn blue. They tend to turn a golden yellow color. It is chrome that turns blue.

I coated the new exhaust pipes on my Triumph Tiger with a product made by Kreem (see below). After 5,000 miles they still
look like new with just a slight blush of golden color at the bend. It is a good practice to get yer bike perfectly tuned with
old pipes before installing the new ones. Yes, it is easy to misadjust a Mikuni with the air screw. This product is an inexpensive solution.

http://kreem.com/blueshield.html

There are a number of high temp paints and ceramic coatings that can be used to coat the inside of exhaust pipes to control
heat. Most are more expensive and some are very very expensive. Do a google search.

I've always been baffled by the pipes on my 750. Bought cheap at a bike jumble (new, but cheap) and fitted 20+ years ago, they have never blued. I don't do parade laps either. True, they have gone slightly straw-coloured sometimes but a quick rub with Solvol gets almost all off. back in the '70's my Commandos did blue 'em up, but these cheapies are still going strong. I'm confused as to why.
Cheers, Martin

Blued chrome is a function of temperature. Actually, all colors of chrome are oxides of chrome and are a function of the temperature at which the oxidation occurs. Blue/purple is where the temp is hottest, going to blue, then yellow (gold) as the temperature becomes less.

As Dances says, excessively retarded ignition causes more fuel to burn in the exhaust port/pipes .... more heat in the exhaust port, and higher temperature, and less heat in the cylinder where you want it. Conversely, excessively advanced ignition causes more fuel to burn in the cylinder, where you do want the burning to occur, just not TOO advanced, or overheating can occur.

A lean mixture runs hotter.

Removing the blue with chemicals or polishes is removing chrome as well, exposing the underlying chrome to become oxidized in time. Eventually, if one keeps removing blue with polishes, one will have no chrome left, just the underlying copper base plating. If one leaves the blue as is, the blue protects the underlying chrome from further oxidation.

Coatings inside the header pipe act as an insulation which reduces the surface temperature on the outside of the pipe. Lower temp results in less blue.

Slick

EDIT: A lean mixture runs hotter in the cylinder

Hey Tex, you just mentioned that retarded ign causes more fuel to burn in the pipes, causing bluing. Does that necessarily follow that a rich mixture will do the same.
I was told one time that rich mixtures caused the blueing. My 750, from new, always had a golden hue. My 850, was blue when I bought it about 10 years ago.

Some years ago I go sick of my bike only doing 45 - 50 mpg so I worked on the carbs. As a result I now often get 65 mpg. My blue pipes are starting to golden up a bit. ??????????????????????????????????????????????????????????????

Why would that be.

Go Figure because I dont know how to explain it.

I am getting ready to do the length of NZ and back next month, so have considered putting on the brand new pipes I bought for my 750, as I have been running my bird-shit arc welded l/h pipe for the last 4 years. Can always buy another set for the 750. Might prove myself wrong about this bluing thing.

Dereck

Rohan said:

Have him check that his auto advance/retard unit is advancing and retarding - when it should be. Needs a strobe timing light.

Running lean will also do that, doesn't have to be very lean to push the zorst temps up.

Can buy a polish thats supposed to take the blue out of blued exhausts - apparently works, to a degree - some chrome blues more than others. ??

Click to expand...

+1

Excessive bluing of the header pipes means something is not right, running to lean for one thing, I have heard a lot of people blaming single wall pipes for this problem, what a load of B/S, when I built my Commando/ Featherbed in 1980 I got my header pipes made up by a car exhaust shop that had a mangle bender, used normal car exhaust pipe which is single wall and lucky there was a chrome shop next door, well after 35 years now and over 140k with them my pipes have never blued, they are getting a bit thin at the top bend (had to braze up one small hole in one of the headers but that was a few years ago now), if your bike is set up right, turned right then your pipes shouldn't go blue at all.
When I brought my new Triumph Thruxton in 2013 the header pipes started to blue up straight away, but I blocked of the air injection system it stopped straight away, the pipes are single wall as well, so if your pipes are going blue means there is to much heat and there got to be a reason for it.

Ashley

Don't be blaming the pipes. And yes it's about too much heat. If he's running points then the advance weights and bits can stick if not lubed regularly as the manual states. That's behind the points plate which will need pulling. Electronic is easier to deal with. Maybe his pilot jet(s) are gummed shut creating leanness heat. I do coat any new header pipes internally with a heat paint before any fitting and startup. Helps for sure.

@kerinorton

Hey Tex, you just mentioned that retarded ign causes more fuel to burn in the pipes, causing bluing. Does that necessarily follow that a rich mixture will do the same.

When analyzing how ignition timing or mixture affects exhaust temperature, the key point to remember is that combustion of fuel requires a finite time. Fuel atoms, or more precisly fuel ions, must find and react with an oxygen ion before the exhaust valve opens, otherwise the reaction will take place in the exhaust system, raising exhaust temp. Advancing the timing provides more time for the reaction to occur in the cylinder, and retarding the timing less time.

Leaning a mixture reduces the mass of fuel relative to the mass of air in the cylinder. There are fewer available fuel ions and relatively more oxygen ions. The time required for fewer fuel ions to find and react with relatively more oxygen ions is therefore less, and virtually all the reaction occurs in the cylinder, producing useful work with minimum fuel consumption, higher cylinder temps and lower exhaust temp. Richening the mixture, increases the fuel mass and reduces, relatively, the oxygen ions. Thus the time required for the reaction to become essentially complete becomes longer with increasing richness, and may spill over into the exhaust system. Excessively rich mixtures lack the oxygen to burn, and the fuel goes out the tail pipe as raw hydrocarbons or as free carbon (black smoke).

When fuel combusts in the exhaust system, it results in a crackling and popping sound.

Slick

Hi slick, I am a mechanic and yes i agree with what you say. I was sort of stunned when it was suggested the rich mixture caused the blue pipes and the leaner mixture caused the gold colour. Never really had a chance to prove it but my blue pipes on the 85o did start to go gold-ish when i fixed those mixtures. Go figure. I certainly cant explain it . Thats why I question theories on tis site. The proof is in the pudding they say. As Blaisestation and Gortnipper are likely to ride with me, there will be witnesses to whatever happens.
I guess we will find something out when I fit those new pipes.
Dereck

The only fix is to coat the insides of the pipes, either with carbon or heat-resistant paint. single-layer chrome pipes discolor and the hotter they get, the bluer and further down they will discolor. Using a product like Blue-Away will remove the discoloration, but will also remove the chrome and you'll end up with dull bare steel and then rust.

Before you jump on the Mikuni you need to know:

1) If the installation produced air leaks. I have sold a fair number of these kits and have found some well meaning would-be mechanics that think screw drivers are machines...

2) How is the Mikuni jetted? The possibilities are pretty broad and vary with temperature and altitude.

3) Slow speed operation: If you get caught in traffic frequently your pipes will blue quickly.

4) Cam timing: If your cam is retarded enough, you can blue the headers to the second joint in less than 10 minutes.

5) Ignition timing: too advanced or retarded produces the same results as # 4 above, just takes a bit longer. For those of you that are still running points consider that the springs that "control" the bob weights may be up to 47 years old, if so you can easily get full advance just off idle.

It's over 4 years since the OP had this problem.

He may have sorted it by now.

Old topic yes, but I just finished setting up my new SS header system and have coated the innards of the new headers with hi-temp ceramic, should keep any discolouration to a minimum