engine backpressure ? and straight pipes

[basstracker]

So I have heard that running straight pipes usually burns out your valves because of lack of backpressure. My question is if a 1990 fzr 1000 exup has a valve the adjusts backpressure would there be any issues of running straight pipes?

[DonTZ125]

It burns your valves because either a) you run too lean because the restriction of the muffler is gone, greatly increasing the airflow through the carb, or b) because you're actually sucking fresh air all the way back to the head. This is normally hard to do, and normally happens from people rebuilding their engines and dicking around running the engine without ANY pipe.

There is no great performance advantage to be had in running without a muffler, and the possibility of damaging your engine, your hearing, and the sport's already tattered reputation. Just leave the damn muffler on.

f*ck me, I'm in a pissy mood tonight...