Topic: CB650 exhaust issue

[BrianWood]

I’ve been slowly going over my 79 CB650 and trying to rebuild anything that looks like it needs it or doesn’t work. A couple of weeks ago I had to take one of the headers off to access a bolt and I noticed the exhaust gaskets were pretty beat, so I pulled off both sides and ordered new rings. While I had everything off I decided to change the plugs (which turned into an hour long metal sculpting project involving an 18mm socket and an angle grinder), so once I had new plugs in I fired the engine off, admittedly just to see what it sounded like but I convinced myself it was to see if new plugs made the engine run better. When I started the engine, I had blue flames shooting out of the #3 exhaust port but not any of the others. I’m pretty sure this has been happening for a while, at least according to the header pipe. Can anyone out there clue me in as to why this would be happening?

Thanks!

[American Locomotive]

That'd be unburnt fuel, burning out the exhaust pipe. Could be from late ignition, to that carb being a little rich. Many different things. You really shouldn't be running the engine without some kind of pipe on the exhaust ports anyways.

[BrianWood]

Thanks for the info, I really appreciate it. I know I shouldn’t have run the engine without the exhaust pipe back pressure so I only ran it for 10sec or less, but now I know I have a valve adjustment in my future!