Exhaust ports

[TR34]

What do you guys make out of this picture of my engines exhaust port. Clean port has a carbon build up on the valve stem and I think that is the side where the secondary air port is. All the other exhaust ports are the same . One side clean, other dirty. I was planning of plugging the tube right after it exits the air box housing for next year. Is there anything I can do to prevent this build up before it gets worse.
Thanks.

[TR34]

Well, I guess I will talk to myself!  Spark plugs are really nice at this mileage so no worry about burning oil or having a bad map. Now, is it possible that from the air box , mixed fumes of crankcase are mixed in to the clean air ports? I have to double check to see which one of the two ports have the clean air ports (reed valves) lined up.

[gPink]

TR, maybe nobody who has been on the forum since you posted has looked in their ports. I haven't so I couldn't answer your question. Maybe someone who has will post up.

[VirginiaJim]

Not something I do on even a semi-regular basis....  Agree with Gary on his summation.  You might try running a fuel system cleaner such as Techron or something similar every once in awhile.  Which reminds me that I probably should do that as well.  I'm getting ready to change the oil so running some through now might be a good idea.

[TR34]

Thanks for the replys guys. I have just noticed that myself. I guess every year I going little bit deeper in to this bike. I can't seems to leave things alone. Since It's winter now for me that I can't ride for another four months or so, this is the only therapy for me. Go down to the basement and try to see what I can and cannot do with the bike.:-)

[gPink]

Let us know what you find out.

[rwulf]

What you see in the exhaust port in related to what you put into the engine.
You might try changing your brand of gas and see if it makes a difference.
Dark area around valve stem would be caused by a cooler area of the port,
possibly related to engine not warming up. As in short trips.

[TR34]

Since it is the same piston port it is just divided in two at the exit, wouldn't you think it would be the same on both ports or valves?

[The Pope]

What do you guys make out of this picture of my engines exhaust port. Clean port has a carbon build up on the valve stem and I think that is the side where the secondary air port is. All the other exhaust ports are the same . One side clean, other dirty. I was planning of plugging the tube right after it exits the air box housing for next year. Is there anything I can do to prevent this build up before it gets worse.
Thanks.

I think that the air port is what is causing this. So closing it off would be what I'd try first.

What you see in the exhaust port in related to what you put into the engine. You might try changing your brand of gas and see if it makes a difference.

With this being only on one of the two exhaust valves (per cylinder), I don't think the brand of gas is the issue. Because if it was, all of the exhaust valves would show this build-up.

Dark area around valve stem would be caused by a cooler area of the port, possibly related to engine not warming up. As in short trips.

The cooling of this area could be being caused by the relitively cooler air coming from the air port.

[C1xRider]

I beleive the exhuast port is split between what's coming out of the combustion chamber (both valves), and fresh air from the air injection to supply oxygen to help the catalytic converter burn any remaining unburnt fuel.

In your picture, the right side should be what's coming from the combustion chamber.  As for your actual question about the build up around the vertical shaft (stem?) in the left side, I don't recall seeing any of that when I've had my header off (though it's been awhile).

It does look like carbon buildup, but there shouldn't be any exhaust gas exiting there.  It's possible that gas fumes build up in the airbox, from slow speed stop and go driving, then get sucked into the air injection and passed to those ports.  Since it would be raw fuel, it might be collecting there, as the narrowest point in it's travel with the highest temperature, and building up as tar / gum.

Can't be sure, but it's the only theory I have for you at the moment.  Hope i

[TR34]

I did double check the pair valve ports and as seen in the picture on the lower side and right behind the valve stem is the port. So, there is no question, air temp difference and mixed fumes are the cause of the color and canon build up. So, I will plug the pair valve tube and check it at the end of the next season. This will be much needed since I am planning of getting a muzzy dual set up and install K&N air filter, so when I take it to a dyno to get a map there would be a correct afr reading. At least that is the plan anyways. Thanks for all the reply you guys gave me. Highy preciated.

[rwulf]

I miss understood. It sure looks like an oil deposit. If it's on all of the valves on the
left valve guide and every left valve guide looks the same you maybe on the right
track. How does the oil lay in the cylinder head when the bike is parked on the side stand?
Does oil pool next to or around the valve stem?

[TR34]

It is only on the valve ports where clean air system goes to. Which is alternating ports so they are not all the left or  right valves. I do usually park on the center stand . And  I would guess, oil is mostly collects in forward edge of the valve stem .

[Son of Pappy]

Here's my take, with a twist.  What is the purpose of the PAIR air?  What is the most likely source of combustable material not burned in the cyclinder?  I'd run a couple of tanks with a good injector/fuel system cleaner through the tank with the PAIR valve plugged.  What I think I see is the burned contaminated portions of the fuel that have accumulated in the area most disturbed by flow.  Think of a bridge after a storm.  I also think it is a sign of an overly rich setup, do you run a PC or similar fuel control system?

[TR34]

Allright, so what you are saying in an other words; maybe it is a coincidence that color of the ports on each cylinder exhaust ports are lined up with the pair valve ports? And this is a picture of my spark plug. They seem to all the same. I have Jamie's map for my st up.