Okay what would happen

My mufflers are old and need to be replaced. What would happen if I took them off and ran with just the head pipes until I saved for new mufflers? Would the bike still run okay or what? As far as the noise goes, I don't care.

 

Not good. Apparently running an engine without any backpressure can be fatal. Supposed to be bad for the rings and valve gear.

Of course I have no specific proof of this but even a high performance racing engine has some form of muffler.

My advice, Don't do it.

 

The carbs would be so lean that the bike would not run well at all. Remember that changing from a stock ehaust to a 4-1 requires and increase in jetting due to lowered back pressure. Straight headers would bring the pressure down to a minimum. Without rejetting it can't run well.

 

How can this be? Harleys and other bikes run like this all the time without trouble. I read somewhere that running without the mufflers will increase the overall power of the bike. 4 into 1 is what I want to do, but I can't afford it yet.

 

Other than the maintenance manual stating "Do not run the machine with the exhaust baffles removed" I am unaware as to why. I can, however, say one fellow I know did and the bike (an 82 750) ran like crud. The back pressure is a necessity with the carbs used on these bikes, not an engineer (yet) but I don't argue with what works. I need to make a clearification of an earlier post. The carb types are not the CV as I wrote, but a CD (constant depression). I am aware that the HOG boys run open pipes (thanks a bunch guys, I love noise at 2 am, really) and yes, for a normally aspirated carburetor, this helps. But in this instance, these do not function in exactly the same way and do require a bit of back pressure or the fuel mixture leans out badly (remember, these carbs normally run "proportionally weaker than that of a conventional slide-type" and this adds up to an easy way to burn out valves and motors if your not careful). I think you should error to the side of caution and preserve your asset, lest it fry from an untested modification. I hope someone with a bit more knowledge comes along and answers this burning question for us.

 

when you say that reducing backpressure should increase power you are right... sort of. On new bikes and cars that use EFI (electronic fuel injection) then yes this is the case, as the computer automaticly adjust the fuel mimxture, keeping it constant, which means when the engine breathes easier, it runs better to. So if you slap a turbo on, the computer doesnt need to know anything, it just keeps doing its job adjsuting the fuel mixture as needed.

However in a carbureated (spelling?? its late) engine, the carbs are tuned to the application, meaning that if you make an adjustment to the engines ability to breathe, you then have to adjsut the carbureators to compensate. In short could you run your bike with straight pipes? theoretically yes, if you retuned your carb.

BUT! when making comparisons keep in mind that a harley is an ENTIRELY diffrent machine. For starters harleys are mostly V engines, which typically have lower compression ratios, and higher tourqe at lower RPM's, also they are domestic. Our bikes are inlines which typically have a higher compression ratio, lower tourque, but more HP, and a wider powerband, including a higher redline, aannnnnd they are japanese.

So dont think that "a bike is a bike is a bike" this is no more true then a honda civic is the same as a ford F-350 superduty. just something to keep in mind.

 

Okay I get it, leave it alone. Thanks for the answer it made sense. But I will get rid of those stock mufflers, there just to ugly to keep.

 

no mufflers=burn down. Don't do it.

 

perhaps give them a quick polish for now? i hear some pine-sol, ajax and hot water can do wonders for chrome and other polished metals.

also check out some grade 00 steel wool, might help as well.

 

"Never Dull" does wonders on 'ugly' chrome.