Without doubt, the bulk of the technical questions I receive are connected in some way, shape or form to aftermarket exhaust systems. That should come as no surprise. The aftermarket exhaust business is huge, so installing some sort of pipe is almost a prerequisite to owning a cruiser. While I don't particularly mind repeating myself, it's something I apparently do on a regular basis according to Mrs. Zimmerman, I thought it be easier on all of us if we reviewed a few of the more common questions that pertain to the installation of an accessory pipe. Call it Pipe Job 101, if you will, and keep those cards and letters coming.
What's the best pipe for my bike?
I get this one a lot, and the short answer is: I don't know. For starters it's impossible for me to test every known brand and type of pipe on every model of motorcycle. So in many cases, like you guys I have to rely on feedback from other riders to tell me what works. The drawback to that approach is that "most popular" isn't the same as "best," and I'm sure you can appreciate the distinction, so I'm always loathe to say it's this, that or the other pipe based strictly on hearsay. But the bottom line is those pipes didn't become the most popular because they were junk. So if you pin me down on what's the best pipe for your Yamaguchi Firebelcher 1000, and eight out of ten guys tell me it's the Wind Breaker Flatuance Five then I'm probably gonna suggest that's the way to go.
How much horsepower will I gain if I install an aftermarket pipe?
OEM exhaust systems are very, very efficient, so simply installing an aftermarket pipe doesn't normally net you a big horsepower gain. In fact, whenever we've dyno tested pipes, (see Pipe Dreams, Aug 03 and Pipe Dreams II, Dec 07) we've been dismayed to find that many pipes actually reduced horsepower, which is a real bummer if you just dropped upwards of 600 bucks on a set of pipes. Why this is so is a separate article, but here's the bottom line: If you want to see an increase in power, (and by increase I mean pick up maybe 10 to 15% more torque and horsepower) you'll have to go for the whole nine yards, so along with the pipe plan on adding some kind of modified air box kit and rejetting your carburetor or remapping the EFI. It won't be particularly cheap, but as far as bang for the buck goes, it's your best option.
Mark,
I installed a new pipe on my bike and it turned blue before I even started the engine. The mechanic, Otto is his name, down at Ferds Feed and Motorcycle shop where I bought the pipe said it's normal. My question is why would anyone name their kid "Otto"?
Wondering
Poke and Plumb, AK
If I only install an aftermarket pipe will I have to rejet or remap the fuel system?
The answer here is a qualified maybe/probably/but not necessarily. Typically aftermarket exhaust systems are less restrictive than their OEM counterparts so carburetors normally need to be re-jetted or EFI systems remapped to cope with the increased airflow.
But by no means is that a hard and fast rule. I've installed a few systems lately that didn't require any changes to the fuel system, and while those pipes aren't in the majority (yet), there's enough of them out there to warrant discussion. On the face of it, I'd say yeah, chances are if you install a full system you're going to be fiddling with the fuel delivery as well, but check with the manufacturer beforehand, you may be pleasantly surprised. I also think that down the road the "no-Jet" pipes are going to be getting more popular, especially if the states start cracking down on motorcycle emissions.
What's the difference between a "slip-on" and a "full system?"
While I'm usually tempted to say 500 bucks, my mom always taught me not to be rude. The difference is of course that a slip-on is just that, the stock mufflers are removed but the OEM head pipes retained, the new mufflers, if they can be called that, are than "slipped on" to them. On the other hand a full system is as its name implies a complete header to "muffler" exhaust system that replaces the stock set up from one end to the other.
As a generalization, slip-ons are easier to install and seldom require rejetting to function properly, they are also relatively inexpensive. On the other hand a full-system normally requires modifications to the fuel system and costs a bit more, but when paired with the right intake tract modifications provide a greater increase in power.
I'm not sure if I'll like the sound of the pipe I'm considering, is there any way to hear one in advance?
The first time I was asked this question it pertained to a Vulcan 1500 and one of the more popular aftermarket pipes. Back then I suggested the writer head down to the local Kawasaki shop or his favorite biker hangout and try to find a bike like his, wearing a set of the pipes he was considering, and politely ask the owner to fire it up for him. I'd still argue that's the best way to judge the aural quality of a pipe, but like many things, in the intervening years technology has outpaced me and these days many of the manufactures and quite a few of the owners forums have sound clips that you can listen to. Frankly I don't think those do the pipes justice, after all you're listening through tiny little speakers, with a volume control, so how realistic can it be? But quite a few guys tell me they've bought pipes they're happy with, based largely on what they heard on a web site. So I'd definitely suggest you punch up your favorite pipe builder's website and put on the headphones. If nothing else it'll give a completely new meaning to the expression "piped in music."
Mark,
What's all the hub bub about blue pipes anyway? I've been riding since 1936 and my pipes are just about rusted through. My bikes exhaust system ain't so hot either. What was the question?
Bill "the plumber" Smith
East Bumwad, Texas
I installed a pipe and jet kit and now the bike backfires out the exhaust when I shut off the throttle, what's wrong?
I answer this one at least once a week, and by no means is it a question exclusive to aftermarket pipes. First what we're talking about here is technically known as an "after fire," not a back fire, but that's a fine distinction when your bike pops and bangs like a '55 Ford with a cracked exhaust manifold every time you roll off the gas.
There are several different types of backfires. The ones that erupt on the intake side of the engine, or loud intermittent booms that suddenly erupt from the exhaust are generally caused by mechanical problems. However the rhythmic exhaust popping that occurs on deceleration, especially when an aftermarket pipe has been installed is caused when small amounts of unburned fuel make their way into the hot exhaust and spontaneously explode from contact with the hot metal.
Ironically this normally occurs because the pilot mixture is too lean, rather than overly rich. Here's what happens, lean mixtures tend to burn slowly, and incompletely, so when the throttle is suddenly shut at road speeds combustion is incomplete, the pilot jet is just too small to supply enough fuel under those conditions. The unburned fuel flows out the exhaust valve where the hot exhaust pipe ignites it with a bang. Nine times out of ten all it takes to cure the problem is a slight richening of the pilot circuit, if your bike has a carburetor(s) a half turn richer on the pilot screw should do it. If you've got EFI go one step richer on the low speed screw of the module, you did install a "cheater" (adjustable EFI) module didn't you?
Other things that can cause an after fire on deceleration include exhaust system leaks, leaking air injection systems, vacuum leaks or anything that allows combustion supporting fresh air to enter the exhaust system when the throttle is closed. If the popping starts a few rides after you've installed a new exhaust system, my first suggestion would be to retighten all the exhaust clamps, particularly the ones at the cylinder head.