cobras and burnt valves

[cma1]

anyone have a problem running cobra pipes without re-jetting a few sizes larger ? it would seem to me that opening up the exhaust that much without compensating  topside would cause a huge loss of backpressure subsequently burning the valves.

[Patrick]

Lack of back pressure ? Here we go, I ain't touching this one. If you're worried about that, why not just increase the valve lash.

[Gavin_Sons]

Have you seen the inside diameter of the headers? I dont think there is any way to lose enough back pressure to burn a valve.

[Momz]

The sheer length of the Cobras or even the TBRs ensure that there is sufficient heat trapped to keep from burning the valves.

Cut them short,...say just to the rear of the rider pegs,....then you may have problems.

[Chrisj CMA]

anyone have a problem running cobra pipes without re-jetting a few sizes larger ? it would seem to me that opening up the exhaust that much without compensating  topside would cause a huge loss of backpressure subsequently burning the valves.

I bought my '97 in 2002 with 5K on the clock.  It came with Cobra pipes and the carbs were NOT re-jetted.  I suppose I cannot for sure tell you that nothing has happened to the valves, as I have never opened the motor up.  However, it now has 137K on the clock and runs as good as the day I got it. 

[salty1]

+1 as to what Chris said. Mine has never been rejetted and runs absolutely fantastic! I hope I get as many miles too.

[cma1]

hard to argue with 137K huh ? o.k. i guess i'll put them back on. didn't have any luck selling them, shipping too high.