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.