Back pressure

rappz7

rappz7

New Member
If i go from 26 inch mufflers to 17 inch mufflers running a stock intake system will there be a back pressure issue? I have a 1979 cb650 and Ive heard that shortening the mufflers may have this effect. Anybody have experience with this?
 
Just any old muffler? Care to elaborate? Is it a straight pipe?.....Did it come off another bike or is a shiny and store bought one? .....a little bird once told me that Hondas Suck....I wonder what happened to that fucker......
Anyways if you slash cut the pipe at the header you will most likely fuck your valves ....if you have a muffler it will be good....unless you consume too much aspertame
 
DesmoBro said:
Just any old muffler? Care to elaborate? Is it a straight pipe?.....Did it come off another bike or is a shiny and store bought one? .....a little bird once told me that Hondas Suck....I wonder what happened to that fucker......
Anyways if you slash cut the pipe at the header you will most likely fuck your valves ....if you have a muffler it will be good....unless you consume too much aspertame
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It's an EMGO reverse cone shorty megaphone exhaust muffler. They are not stock mufflers. These are a bit smaller at 18 inches than stock which were 26 inches.
 
Thats probably going to flow more Than the stock and may give a flat spot if you just ditch the old one and stick that on....you may want to get a high flow air filter to match and.... jet the mains and pilots in the carb.....Its a trial and error sort of thing....You could get lucky and be fine ....but you want to be ready to either go back to stock or squeeze that lemon for some more juice
 
DesmoBro said:
Thats probably going to flow more Than the stock and may give a flat spot if you just ditch the old one and stick that on....you may want to get a high flow air filter to match and.... jet the mains and pilots in the carb.....Its a trial and error sort of thing....You could get lucky and be fine ....but you want to be ready to either go back to stock or squeeze that lemon for some more juice
Click to expand...

Thanks for the info
 
Normally i dont say that much ....but ive been there making changes thinking im a rocketscience builder....only to end up making them worse....
 
DesmoBro said:
Normally i dont say that much ....but ive been there making changes thinking im a rocketscience builder....only to end up making them worse....
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I'm by no means trying to make this bike into something its not. The engineers responsible for these bikes built them to perform as they are and its a bullet proof design. I just think the shorter pipes give it a sportier more minimalistic look which is what I'm trying to achieve. If i have to re-jet/tune than so be it but it would be great if I didn't have to. I guess Ill just have to wait and see. Swapping out the mufflers is really my only choice unless I wanted to drop hundreds on a quality system and finding a stock one that isn't complete crap is next to impossible. I know because Ive been keeping my eyes open now for almost 2 years. Sure there may be a few nos exhaust systems out there but they sometimes go for more than a quality after market system.
 
Swap em and see, if your performance suffers, you need to make adjustments. Carb tuning isn't rocket science, just do your homework (google is great)
 
You will want to re-jet if you change to a free-er flowing exhaust. The stock systems are most often heavy and designed to do the job they were made for, reduce emissions, cut the noise and give proper midrange power.
If you free that shit up you drop some weight, get a nice sound (depending) and it will most likely flow better at the top end, but probably knock of some torque at the low end due to the loss of exhaust velocity.
It all depends what you want from this bike.
 
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