2006 exhaust super stinky


Junior Member
When I first got my 06 on 11, it didn't really smell. Over time, it has gotten really strong. It has a pretty clean stock yammy filter, I replaced it year or 2 ago, but it is still good as not many miles have gone through it. I put in iridium plugs a couple years ago. I DID have a gasket leak, my suspicion is the cat pipe to muffler joint, but I replaced both. I did this as my legs would reek after a ride. Now, the legs don't reek, but my back still does.

So, I am wondering if the engine is rich. I haven't had time to pull the plugs, especially since it is such a pain the butt, and I have large hands. Can we say xxl gloves. Last time I did plugs, I had to drain part of the coolant, to make enough room for my hands.
But, normally exhausts only stink this bad when rich. I also have what sounds like a miss at low rpm. It pops at low rpm. However, the bike accelerates well and has great response, so I am pretty sure I do not have a miss.

I came across this co adjustment thing, and thought it might be at least worth checking out. I know I need to hook a wire to another wire and then use the display.
What are the "stock" c1 and c2 numbers generally supposed to be? Keep in mind, the bike is all stock as far as the exhaust is concerned, same with fuel system. Only non-stock are the plugs.

are there things to really keep an eye out for, when I do this? I know to write down the numbers I initially find, so I know what I started with.

Gary in NJ

Junior Member
Site Supporter
What year is your FZ? If it is the model with the O2 sensor I would suspect that. What does the exhaust smell like? If it’s rich it will smell like a 1970 Chevelle with a 396 and a 4bbl carb. If the cat has gone bad it will smell like someone is lighting matches.


2007 FZ6
Site Supporter
There are no standard #'s for the CO settings.

On every bike, they'll be different(stock, factory setting). As you noted record what your are before adjusting anything.

It would be best to check the plugs..

Couple questions.
-When dead cold, do you have the slightly higher "warm up idle"?
-And if so, once warmed up, does it drop down and sound like it idles normally?
-Any black smoke from the exhaust when revving the bike?

If you can post a good video of cold start up, the idling down, and especially the warm idle.
(If real bad, it can be heard)..

Have you ever figured out your mileage (before and after)? That, depending on how you ride, would give you an idea if it's running rich..

***As a side note, another member recently did a valve adjustment and one of the cams was out one full tooth. The bike ran good but the mileage dropped quite a bit. *** Something you may want to check, especially if you bought it used, you don't know if someones been inside and dinked with it...

Here's the link to the above, ^^^, problem and fix:


Super Moderator
Elite Member
Site Supporter
The miss at idle might indicate a vacuum leak.


Junior Member
Well, it's an 06. I got it with less than 2k on it. PO had a small layover with it. Bit of scuffing on bottom of engine, left side; the left slider, and the fairings.Very little, but enough to scare him, I guess. It still has less than 20k on it, I have other bikes. I've pulled very little apart, so I don't think it is vacuum. I've had vacuum leaks on other bikes, and this doesn't sound, or feel, like that. 99% sure it is way rich.
Without a real tach, I can only go by sound. I don't consider a digital block tach to be a real tach. Starting rpm is not much higher than warm idle, it is rather jumpy though. slightly surge-y on overnight cold startup.

I have not gotten to do much riding, so I just filled my tank with fresh fuel. I always dump in seafoam and top the tank for winter storage. However, the smell is not from old fuel, as it's happened for the last couple years. My mpg I'd say on the old fuel, was about 40mpg, city/town.
I think 45 is about my average. I'd say the plugs have about 6k on them, and they are iridium. Even copper should last that long, with little trouble. I will have to check for black smoke, but the stink is there, cold or warm. Maybe slightly less when warm.

I'd say it smells worse than my 78 cb750 when it runs rich.
I am fairly certain it is rather rich. I guess I'll just pull the plugs and see what they look like. Bike will easily get to 100 mph, with plenty to go, but I'm not going to do it.

Gary in NJ

Junior Member
Site Supporter
You do know if you scroll though with the select button on the indicator, there is a digital read out of rpm. What are you using for an air filter? Have you tried changing it? Just because it appears clean doesn’t mean that it isn’t causing a restriction.


Old-School Member
My 04 stinks badly also, but I have a strange feeling it may have something to do with the cat bypass pipe I installed with the quad exhaust..... :)


Junior Member
Well, Haven't had much time to work on things. Took my air filter out, and bike stunk less. The air filter is stinky as all get out. It just utterly reeks. It's not dirty, but I have had restrictive paper filters in the past, usually off-brands such as emgo, but this is a yamaha filter. But it does show that either the injection is way too rich, or the filter is too restrictive.
So, I have to dig around, find the wire I need to ground and get the co numbers. It IS possible to get into a diagnostic state without grounding this wire, but you do not get co numbers, you some d numbers, and it kicks the fuel pump on/off as you select through them. Maybe someone has a manual which talks about this?

Anyways, after the ride today, which was idle up to 75 mph, and 30 miles; my plugs might tell me something.


Junior Member
Well, c1 was -11 and c2 was 6. So I dropped c2 to 0. Plugs are cleaning up, the insulator is light tan. They were pretty rich, the thread ends are really black. So, I think, for now, I am leaving my settings, and will try a different air filter. Seeing as how it stinks so bad, it had to really be restricting.

Next step would be to take a year and move stuff so I can get my xxl sized hands into places and check valves and sync the throttle bodies. Just have to see what shape my mercury sticks are in.