[GSXF]

I believe the problems really come if you run a motor with NO exhaust, like, just straight out of the head. Then you can have temperature-related issues with your exhaust valves, I believe.

For car engine header is part of the cooling equation, hence the straight pipe instead of no header. Since motorcycle is also a combustion engine, I think engineers would use the same design/principle. What I am not sure is that if I run a straight pipe in the Kat, would it hurt the engine??? I want to experiment with it but I don't have to have to transplant another engine after the test...lol Yes, I agree that a good exhaust is not all about horsepower gains, but more importantly consistent gains across the different rpm ranges.

[Astro4x4]

No power to be had from exhausts? Factory exhausts are already so good? Am I hearing all this correctly? Let's say you run an aftermarket exhaust, and jet for it on a 750.... you might gain 8 hp (Ivan claims 6 hp with a slip-on and his jet kit)..... that's almost 10% of your original power that you've gained!

Ya you are hearing right if we are talking stricly exhaust. Add a jet kit etc. and the story changes.

[GSXF]

Add a jet kit etc. and the story changes

Ditto with the jet kit.

[loudnlow7484]

Ya you are hearing right if we are talking stricly exhaust. Add a jet kit etc. and the story changes.

Don't give me that s**t......... that would be a pretty dumb point to make, wouldn't it?! If you add a full exhaust, and don't jet for it, it runs like pi*s, generally. That's like saying running alcohol doesn't make more power. You're right, if you don't jet for it, it doesn't. As a matter of fact, you might trash your motor if you don't jet for it....... that doesn't mean that it won't make more power on alcohol.

Your argument sounded that factory exhausts are so good that aftermarket ones don't do much for performance, which would be wrong.

[Astro4x4]

Dude we were, or at least I thought we were talking strictly about exhausts 'cause no mention was made of motor mods. So ya, you're right.

[airforceranger49]

For car engine header is part of the cooling equation, hence the straight pipe instead of no header. Since motorcycle is also a combustion engine, I think engineers would use the same design/principle. What I am not sure is that if I run a straight pipe in the Kat, would it hurt the engine??? I want to experiment with it but I don't have to have to transplant another engine after the test...lol Yes, I agree that a good exhaust is not all about horsepower gains, but more importantly consistent gains across the different rpm ranges.

bump.... anyone got an answer for this question yet?

[tone]

Hmm lots of confusion in this thread

The simple answer to the above is if you run a bike without any exhaust .....
#1 it will sound ****
#2 it wont run properly once the speed rises to the point that the engine is trying to force out the used gasses against the wind pressure
#3 you will also lose the scavenge effect of the exhaust as there isnt one
#4 if by any chance you do get it to run in a fashion it will run weak & you will burn out the valves

The same things apply to a lesser degree when running just downpipes with no silencer but it can be jetted to suit this setup & run without major problems although its not easy

All the above applies to race exhausts but again to a lesser degree, reletively minor changes to jetting will be needed in most (but not all)cases to get the mixture spot on, not all bikes will need bigger jets as that depends on the particular bike, the exhaust used & the outlet size

Cars running noisy exhausts tend to have only the back boxes changed (in this contry anyway) there is usually at least one other "silencer" & sometimes a cat which will retain back pressure & allow scavenging to a certain degree, also remember cars rev lower than bikes the valve timing is very different & they crank up the revs a lot slower in comparison to bikes but they will still burn out the valves if run on a lean mixture for any length of time

tone

[STULER]

severe backfiring and you toast your engine.

[06katanarider]

I pulled off my exhaust just to see what it sounded like and it sounded like $@#*. When I slowed and geared down it sounded worse and backfired.