Pipes & Jets Problems & Solutions - How-To

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.

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"?
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."

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.

I couldn't find a jet kit for my 1966 Greeves 250 Silverstone racer, so I made them out of a couple of old Whitworth sockets. My problem is that I now have no sockets left, so I can't reinstall the carb. I'm told this is a good thing. Is it?
Sir Alfred Angus Hereford III,
Lord of the Dance.
Dolittle, Scotland

Will installing an aftermarket exhaust system harm my motor?
This one is sort of a ringer, but the quick answer is no, a properly installed exhaust, with correct fuel management will not harm your engine. Of course if you're incessantly revving the thing up at 2 AM and some engaged neighbor takes a sledge hammer to the jugs, then yeah, some damage is probably inevitable, though how much depends on the size of the neighbor and his dedication.

How come my bike surges at low and moderate throttle openings since I installed my pipes?
This is another fuel management issue. By and large small throttle opening surges are caused by lean EFI or carburetor settings so the cure is straightforward. If it's happening somewhere between idle and maybe 1/8 throttle, fatten up the pilot/idle circuit. If the problem occurs between 1/8 to 1/4 throttle the problem may be in the pilot circuit or it might be in the needle height/midrange adjustment (EFI). Because there's a fair amount of overlap between fuel circuits at small throttle opening my inclination here is to richen the pilot circuit first, if that doesn't cure the problem, you'll need to richen the midrange slightly. If that makes the bike too rich, go back and lean the pilot side out a bit.

Why did my new pipes turn blue?
I dunno are they're depressed? Many aftermarket pipes turn blue at the cylinder head, and usually for some of their length afterwards. Self appointed experts will tell you it's because the bike wasn't jetted properly or you let it idle too long or left the choke on too long or whatever else they've decided the problem is. Bull, unless the pipe is blue from the exhaust port to the muffler outlet, what you're seeing is nothing more than the affects of high heat on chrome. Here's the deal, most of the OEM manufacturers (and there are a few exceptions here) use a double wall construction, one tube inside another to build their header pipes. The inner pipe carries the exhaust; the outer one is there for appearance. Because the inner pipe does all the dirty work it discolors and leaves the outer one shiny and bright. Many aftermarket systems are built using single wall construction and because of that they tend to discolor. Yes, allowing the bike to idle for a lengthy period will discolor the pipe, as will anything else that creates a lot of heat, but no matter what, all single wall pipes will eventually discolor to some degree.

I replaced the engine in my 03 Suzuki Intruder with a Wright 975(E) Whirlwind engine that I pirated from a 1926 Ford Tri-motor. As you may recall the 975 (E) is a Supercharged 9 cylinder radial, that makes 420 HP at 2400 rpm. If I replace its Stromberg carburetor with a HSR48 flat slide Mikuni do you think I can achieve a more consistent idle?
Southbury CT

Will installing an aftermarket pipe void my warranty?A loaded question if ever there was one. According to the Magnuson-Moss Warranty Act of 1975, and I'm paraphrasing here, the installation of an accessory doesn't void a vehicles factory warranty. It can however result in the denial of a warranty claim that results from a problem caused by that product.

To use an extreme example; let's imagine your relatively new cruiser, equipped with an aftermarket pipe, burns up an alternator, investigation shows there's no connection between the alternator and the pipe, so the factory must cover the repairs under warranty. However three weeks later the bike holes a piston. Here's where it gets sticky, if the pipe made the bike run lean, causing the piston to overheat and detonate, you're liable for all the costs of repair, however if the pipe was properly installed and there are no issues, like an improperly mapped EFI, then the problem should be corrected under warranty. As you can see there's a lot of wiggle room here, and the discussion between the broken bikes owner and the factory can get contentious, but in the main, if the pipe isn't directly responsible for the problem, the breakdown be covered under warranty.

What are the legal ramifications of installing an aftermarket pipe?
Actually, hardly anyone ever asks me this one but they should. By law the federal government, or more correctly the EPA and the DOT set minimum standards that every motorcycle must meet before they can be legally sold in this country. While the majority of those laws cover things like side reflector size, tire sidewall nomenclature and the width of the taillight lens there are standards for exhaust noise and pollution emissions.

However, there's a catch. Although the Feds set the minimum, the states, along with the counties, towns and cities that make them up are empowered to create their own, more stringent regulations if they want to, so long as those additional regulations do not interfere with interstate commerce. For example California's Air Resources Board has emission laws that are more stringent than Federal requirements; currently Royal Enfield motorcycles don't meet them so they can't be sold there. Nonetheless, if you own a Royal Enfield that's registered in another state it can be legally ridden in California because to prohibit its use would interfere with interstate trade.

Here's where it gets scary. While the federal government strongly recommends that the states and their entities adopt the in place EPA noise regulations, and to my knowledge all of them currently do, there is no law that requires them to. So if some state, city or county suddenly decided that the current EPA standard of 80 (dB) was too lenient they could certainly pass, or at least propose legislation that lowered it to say 70 (dB).

I don't know of any place that's actually done that, and it'd be a difficult law to enforce, but there's no legal reason they couldn't and in fact some localities have passed some draconian exhaust pipe laws in an effort to combat excessive noise. For example; in 2007 Denver, Co, decreed that any motorcycle manufactured after 1982 that was operated within its city limits had to have an OEM type EPA engraving on the muffler stating it was an approved exhaust system. If your pipe wasn't so stamped you got a ticket, no ifs ands or buts. It didn't matter where you lived or where the bike was registered, if you rode through Denver your bike had to have an OEM/EPA seal of approval.

By no means is Denver the only town to have passed such an ordinance, only the latest, and I expect to see more legislation like this coming in the near future, but that's a separate conversation. As a side topic, enforcing the law is the responsibility of the state, or the locality that passes the law, and if there's any bright side here it's that they're notoriously lax.

The other side of that coin is the pollution issue. If your state has emission testing in place and your bike fails because you've changed the exhaust and remapped the fuel settings, you're going to have your work cut out for you getting it to pass. And that my friends can get mighty expensive as Jesse James found out to the tune of nearly 300 large when he ran afoul of CARB.

So the bottom line here is that every state is different, and the law being the ass that it is, enforcement issues change day to day. But if nothing else I'd recommend hanging on to those stock pipes and air box, you never know when they'll come in handy.