any type of mod whether incoming (air, gas or nos) or exitting (exhaust) the engine needs to be re mapped or jetted in your case properly to benefit from the changes. The important thing to keep in mind is air/fuel ratio. So if you just added straight pipes and not do anything else. Your butt dyno is giving you the correct reading.

 

now lets say i jetted my bike to match the straight pipe. would i still need to worry about burning my valves?

 

No, as long as it's jetted properly. The purpose of jetting carbs or re-mapping is to acheive the proper air/fuel ratio for your mods to prevent the bike from running too lean or too rich. If your running too lean, this can cause spark knock/detonation, which can cause bad things to happen to your pistons!:fire

 

well i got a yosh pipe and i disconnected the canister just for fun and i was ridin it around, i noticed it bein weaker and i think i remember reading somewares that it would lose power... and it did.
now i haven't jetted it yet, but i do like the way it sounds more this way. i hope theres nothing wrong with running open header on a bike as long as it's tuned for it, i don't wanna believe it does harm, i wanna know if theres any gain vs the slip on since you do lose some backpressure and the yosh is pretty free flow to begin with. BTW i got a carb'd 01

 

You're gonna be asking to get pulled over especially in CA. Generally, the power curve shifts towards the high end without back pressure. So you lose torque and mid-range.

 

Back pressure ≠ low end

Exhaust velocity = low end

Changing the pipe behind the mid pipe wont hurt low end.

 

so there's no power loss? i'm expecting a gain up top but a more noticeable loss down low... correct me if i'm wrong.

why can a harley roll without exhaust but i can't?

 

I'm not talking about low-end, I'm talking mid-range loss that goes to the high-end. Read what fiveoh posted above.

You're just asking to get pulled over and telling a cop that HDs get away with it won't do you any good. :fact

 

A good idea on the street? No.

Will you lose power after correcting air:fuel ratios? No

 

ok yea thanks for all that. it draws attention like a muphuka i don't need that, but i do like the raspyness. like a drag bike. if i was free to do what i liked i'd definitely tune it without the can

 

Just make a custom muffler. Take any can you like and cut it to about 40% it's original length. Bam, loud bike.