Muf or no Muf part II

OK guys I had a long talk with my mechanic he says that frying my engine is a lot of BS. That something that has come down from the car industry and that the straight pipes im running are longer then a lot of the mufflers You buy and put on. He has been working on bike for 25 years, he really sounds like he knows what he’s talking about. Please understand im not being a smart A$$ . I would just really like the facts, for me and anyone else that’s may go have to deal with this issue. So my question to you guys is this, Do you know for a Fact it is going to trash my engine or are you just passing on what you have heard from others.

I'm not a Harley specific guy, have no experience. But, generally, if the engine is properly jetted, you're fine. Problem is, make a mod, and changing to a much less restrictive pipe is a major mod on a Harley, you need to rejet (or remap EFI) to get proper fuel mixture. Burned exhausts valves do not in themselves occur from the changing of pipes, they occur from the improper jetting (lean) that the pipes cause and not rejetting after the mod and the high temperatures that occurs because of the lean condition. Be glad it's not a two stroke or you could wind up on your head after a high side when the engine seizes....been there, done that.

Jetting is critical on race engines, not so much on street stuff. The Harley engine might live at leaner jetting just fine being a relatively low output engine, but lean jetting is NOT a good thing even on a street engine. And, why make a mod if you don't take advantage of it with proper set up? Best way to get jetting proper (and I don't know what bike you got, whether it's closed loop, open loop, or carburetor) is to pay someone with a dyno equipped with an EGA to set it up for you.

JMHO based on building and racing metric race engines. CD is the expert here.

BTW, I hope you don't ride that thing through neiborhoods and you wear hearing protection if you got straights on it. Nothing more annoying to the public than straights on a motorcycle. I want at LEAST some muffling. I like to hear that rumble, too, just don't wanna PO the po po, ya know?

Open pipes, Drag pipes, High flow pipes, they all do the same basic thing.... reduce backpressure. They scavenge the exhaust gasses faster. This can actually suck some of the unburnt fuel out of the cylinder before the cycle is complete. Without rejetting, or remapping the injectors, this will cause an excessive lean condition that can burn valves, or worse like burn holes in the top of pistons. Most all mechanics in shops, both mom and pop places and the stealerships will tell you the same thing. I even had a friend running a '69 GTO that had it leaned out to the place he was getting 18-19 mpg if he didn't rod it. I may be able to find the pic of the quarter sized hole in the top of one piston, and 3 others had "melt" damage.

Your bike, you do what you want. If it were mine, I'd not run it that way. And I'd sure not go rodding it around that way, for fear of doing the above mentioned. My advise is free, so take it for what you gave for it. But here it is, my advise is to be looking for a different mechanic.

Later, Brent

Missouri

Yo man... There is a web site www.harleyhelp.com this dude Spyder owns, and he answers that exact same question... Go to the faqs page and about halfway down, is a topic on exhausts... Check it out... I agree, you will lose power with straight pipes..

Yeah, your super duper wrench is right it's a legend from Detroit. Problem is, it is based on fact and if he had ever worked on flat head ford V8's with a big cam and short headers he would have seen a fried exhaust valve or three.

The is not and never was about the length of the head pipes. The point is that you have a bike that is already lean to begin with and removing the back pressure without jetting or at least adjusting the idle mixture and a plug chop or two is a rather unintelligent act for an expert wrench to perform.

If the bike is EFI and an '06 Dyna, I can guarantee you the EFI is all out of whack because the stock ECU mapping will have no reference for the change in O2 in the exhaust.

It is your bike, your decision to make. You have read the opinions here and can decide from there.

my thought on a bike with no mufflers...????? what for? I guess your bike has a warranty so if you like the way it sounds and your wrench will warranty your motor when it screws up..whatever floats yer boat. I don't think it's a great idea though, just a coupla points. Big Brother is really starting to clamp down on this type of thing..noise for noise sake ain't a good thing. You might find in trying to keep the neighbors from getting too pissed off you may be short shifting your bike trying to keep from being noisy..that ain't a good thing neither. I'm not going to get on about what happens to your hearing. I wouldn't do a thing to it untill I got the pipes I wanted for it and then went with a less restrictive intake, a flash ..the bike should work pretty good then. I don't know about you but I work hard for my money..I'd hate to throw it away...enjoy the new bike.