Topic: Am I going to ruin something?

[Dr. Noisewater]

Hey guys, did some searching but couldn't find anything conclusive.

The bike's a 75 CB550f (069a carbs), factory airbox with Uni foam filter, and Mac headers with open Cone muffler. No backpressure.

I put this bike together over the last year and I've only really ridden it a few times now that it's "complete". I've noticed a good amount of popping on deceleration when riding in about 40-50 degree weather. We had a warm day a couple weeks ago and it ran GREAT in the warm, I don't remember the popping.

Is popping due to a lean condition? Would an open exhaust cause lean or rich? Could I compensate by adjusting the air/fuel screws?

BTW, the carbs were rebuilt and have all stock jets, the plugs are new and properly gapped, and I did a carb sync yesterday. Thanks guys!

[Dr. Noisewater]

Did a little more searching and found something about loss of backpressure causing valve slapping - Can anyone expand on that?

[FunJimmy]

I can't comment on the valve slapping, cause I've never heard that before, but free flowing mufflers will contribute to a lean burn. As an engine breathes better, more air flows and therefor requires more fuel. Try adjusting the sir screws first.

[Stev-o]

The popping on decel is most likely caused by the lack of back pressure.  My K4 does it in all temps. 

What do you plugs look like?

[Dr. Noisewater]

Thanks guys, I rode it a little more today and it seems the carb sync actually cured the popping on deceleration. So it seems to be running fine as is, I guess I'm just scared to put a hole in my piston after spending a year putting the bike together.