The International CBX Owners Association

It is ok to run cbx 82 engine without exhaust between 2-5 minutes at idle??

No, it is not okay.
https://www.quora.com/Does-running-a-mo ... the-engine

Why? Would that be different than a drag bike with an open header?

There is a difference between an open header and no header. I wouldn't hesitate to run an open header (with hearing protection), but with absolutely NO exhaust, I would not do it. I am just scared the old wives tales of cold air messing up the exhaust valves is true. It would be really cool (ha, hot!), but not with my motor.

Steve

PS -There is a video somewhere of a CBX without exhaust running.

Here is one:

https://www.youtube.com/watch?v=EVheMtylYyM

First question is why you would want to do it in the first place? Just to hear the bike run? You won't be able to hear anything anyway.

Dave