lean condition because of leaking pipe conn.?

[georgieboy]

Goodday all,
i experienced a lean condition because of that the connection was torn between the header and the backpipe. I fixed it and lean condition is gone. Can somebody pls explain why this lean condition happened. I mean fuel-mix and everything was untouched and i only discovered this cld be the problem. It seemed so unreal at the moment. That a little leak cld make such a difference.

 

[Layton]

What makes you think it was lean?

 

[georgieboy]

layton, it was too crisp at that moment, like it was starving of fuel. And normally when i twisted the throttle the bike clears out with smoke and with that torn connection it didn't produce any smoke.
I am still wundering how to see this in combination with each other.
Wld the fresh air between the header and backpipe create a vacuum that eliminates the backpressure normall seen. Well i don't know by the situation was there anyhow.

 

[atc3434`]

If the leak was big enough, it probably could interfer with the return pluse that pushing most of the fuel back into the engine, after it tries to escape with the exaust. Without that return pulse, you could have a lean condition because of the weakend return pluse. There may be other good explanations as well.