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Hello
I have A 78 HONDA CB400T. When the engine is runing there is what sounds like woop woop woop on the left side. Speeds up when engine rpm's go up. I only heared it after taking off the mufflers. I just got the bike is not runing right. It will idle ok when I try to rev it rpm's start to go up then drop right off let off the gas and will back fire through the exhaust.

First off put the mufflers back on the bike. It was designed to run with the back pressure, and removing the mufflers could lean the mixture up enough to burn a hole in a piston. And that my friend is bad mojo.

Johnj wrote:First off put the mufflers back on the bike. It was designed to run with the back pressure, and removing the mufflers could lean the mixture up enough to burn a hole in a piston. And that my friend is bad mojo.

Yup.