[Andy]

I noticed from Ducati Scotty's pics from his Cali trip, he appears to have the same discolouration as I do.  I'm wondering how many others have this, and what's causing it?  I've never seen that kind of burning/discolouration on a muffler before.

Personally, I don't care about the cosmetic appeal; but, if it's symptomatic of something else, I'd like to know. 

[SSR]

We dont have this problem in the exhaust but its present in the down pipe where it meats the exhaust. Although its really plae yellow and not that dark. We have the down pipe discoloration due to the catalytic converter fitted in the down pipe and it happens due to the heat generated where the cat is placed. You guys have the cat fitted in the exhaust and that portion gets to hot resulting in the discoloration.


In a nutshell, you should not have the discoloration at the place you have now. It could be due to the internals of the exhaust not placed or fixed at the right place or incorrectly.

Its covered under warranty and you should be able to get it replaced.

[qgolden]

Mine is not discolored at all, and I haul around a sidecar.

Back in my Harley days, such discoloration was a result of an exhaust system change without re-mapping the fuel injection system.  That would lend me to think you have a lean condition, but your Exhaust is stock.....

Perhaps an issue with the catalytic converter.

What if the O2 sensor was not working?  Would that throw off the Fuel Injection computer?  Might want to check the wires to the O2 sensor.
 
Just a relatively un-educated guess....   

[Andy]

Back in my Harley days, such discoloration was a result of an exhaust system change without re-mapping the fuel injection system.  That would lend me to think you have a lean condition, but your Exhaust is stock.....

It is running a bit lean.  I had the plug out a few days ago and it is whitish on the prong, tan on the post, though.  There's about 10,000 km (6,000 miles) on the machine.

[prof_stack]

The red C5 demo had some discoloration in the same place, due to the cat converter inside at that location.  That was after only 100 miles.

My C5, with 320 miles, is not showing any of that (yet).

The after-market (for closed road riding only) EFI silencer doesn't have a cat inside so it might be free of that.

But all the headpipes will change color over time, due to the extreme heat right out of the cylinder head.

[Ducati Scotty]

This is standard for newer UCE bikes in the US, I've seen it on many to one degree or another.  The very large stock muffler contains a fair bit of back pressure and a catalytic converter.  The exhaust gases don't usually go straight through a moto muffler, there's a twisted back and forth path inside most of the stock ones.  This gives extra length to put in more baffles and pass the DOT noise tests.  Some aftermarket mufflers are straight through, louder, and less restricitve.

All the turing directions and the smaller spots where the gasses pass through can concentrate the heat of the gases in that spot.  Also, the catalytic converter needs to get hot to work efficiently.  I suspect that area is either a turn point or strangualtion point, whether by intentional design to get hot for the cat or by error/compromise required in the design for another reason.

Either way, it gets hot enough to discolor the chrome there.  You can spend many hours and try to polish it you.  You may succeed, it will surely come back.  Unless the chrome starts flaking off it's just a cosmetic issue.  As mentioned, it's also common to get discoloration near the head where the gases come out super hot and immendiately get impede by a sharp turn.  This is also the reason for the heat shield on the UCE muffler, it gets much hotter than older non cat equipped mufflers.

I think the new accessory EFI Silencer from CMW is smaller and freeer flowing so it's less likely to discolor or get hot enough to melt your boots near the pegs

Scott

[Andy]

Thanks, guys.

The blueing on the header didn't concern me at all - never knew a single that didn't have it.  But the muffler was something new.

Just one more reason to re-do the exhasut system in black when I give it its five-year make-over.   

[r80rt]

It's the cat, it makes the muffler hot as hell.

[Ducati Scotty]

Yes, haven't burned my arm this much since baking school

[ScooterBob]

It's the cat, it makes the muffler hot as hell.

Correct -

[qgolden]

It certainly is caused by the Catalytic Converter. But what condidtion is causing the Cat to get that hot?  It does not happen on most bikes.  It does not happen on Bikes that work hard and haul more than their share of weight? So how can one presume it to be normal? 

All pipes since the beginning have blued or at least yellowed up near the Engine.  Many companies make covers just for this reason, but not the mufflers, not in a stock configuration.

[r80rt]

By it's nature a cat must get very hot to work properly, certainly hot enough to discolour thin chrome plating. Must bikes don't have a cat in the muffler, it's usually ahead of the muffler tucked up under the bike out of sight. They are usually painted black or made of stainless and they discolour form the heat to, It's just not as easy to see.

[qgolden]

I guess I wasn't clear, when I said most bikes I was referring to most Enfields. Mine is not discolored and I do not think most of the bikes here on this forum are discolored.  I do not know how many other bikes have cats in the muffler but there are quite a few these days, Harley has put cats in the CA and SVO bikes since 2006, as of 2010 all the cruisers have them.  Muffler bluing is not a general topic associated with cats in mufflers on the Harley forums that I follow..

I think it is a lean burn condition. and I think if it continues it could shorten the life of the muffler and Cat.  But that is just my uneducated opinion…I would be contacting a dealer…

-Q

[r80rt]

My C5 muffler did the same thing, its now hanging on the wall. How many miles on yours? Mine started to color about 1000 miles.

[Alan LaRue]

Old topic, I know, but my B5 has only 200 miles on it, and the exhaust looks exactly like the one pictured.

Did anyone ever find the need to do anything about it (change anything fuel related, replace the muffler, etc), or is it not really a problem?