Piping a sport bike or cruiser is the most common question we get about upgrades for our motorcycles. That question always makes me nervous particularly if the next question is, “How much does it cost?” Owners pipe their bikes but rarely do the other things they need to do it correctly. Bad things don’t automatically occur, but you can almost never just “change one thing”!

Carbureted or fuel-injected, it doesn’t matter. If you change the exhaust for more power, to change the sound, to make it look better - you probably changed the amount of back-pressure within the muffler and the gas flow through the motor. Whatever it was, whether you like it or not, you changed the flow through the motor.

The cylinder(s) in your stock engine originally got a certain amount of fuel and air mixed together and then burned to create, among other things, exhaust gases, noise and power. The engineer was looking to achieve a ratio of air and fuel somewhere around 14 to 1.

Let’s look at what’s changed by modifying or replacing a pipe… You put in a pipe that is almost always louder and usually makes a claim of reduced back pressure. Fine, it probably does. But what did we really do by installing a pipe with less back pressure? We allowed more gases to flow easily out of the motor. That will pull in more air and a small amount of fuel too. More air than fuel, however. Also, back pressure from the muffler can hold intake gases in the cylinder effectively richening the mixture at lower rpms. Either effect, reducing back pressure and better flow, will lean the fuel-air mixture. Leaning the motor (assuming it was adjusted properly to begin with) increases the combustion temperature and can actually cost you power or take you into a bad area during acceleration like stumbles or hesitation or backfiring on decceleration. You can actually increase or decrease certain pollutants. In extreme cases you can hurt the motor by raising the temperature in the cylinder particularly around the hot parts - like the exhaust valves.

Let’s talk about where we live. In the Philadelphia area (and many areas now) gasoline is a blend of traditional gasoline and ethanol. Ethanol also tends to lean out combustion. It has an oxygen atom that adds air to the mixture. We rarely see rich fuel/air ratios on newer bikes from any manufacturer. They are generally acceptable but on the lean side of acceptable. The ethanol/gasoline in the Philadelphia area just isn’t helping. Take a bike that was running lean with the stock pipe, add ethanol blended fuel and is then piped - you just got yourself a real hot motor.

Please take a look here:

 http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html

Most of your new bike spark plugs are going to look like #23 in this picture - before you put the pipe on!

I never see electrodes like 13 and 14 (some of the “best” spark plug pictures) on a bike unless the bike was made a while ago or has been rejetted already. What we would like to see is a plug like #18 in the picture.

To pipe your bike the right way, you need to consider the effect of the pipe and adjust the fuel supply to compensate for the increased gas flow through the motor. Your spark plugs give you the best indication of what is happening in the cylinder but you need to check them correctly and, to be really picky about it, at a number of different conditions.

Here is a good discussion of what this entails:

http://hmfengineering.com/forums/showthread.php?t=32

Your traditional carburetor adjustment for an aftermarket pipe is a jet kit. On a fuel-injection motor, you need a device to remap (reprogram) the unit. Both modifications will be working towards adding fuel to cover the additional air allowed into the cylinder by the pipe. The jet kits can include new jets and a different needle. It’s a job to figure out the right jet and needle when you have your new pipe on your own bike and it’s no better than an educated guess by the jet kit developer when the pipe can be one of many pipes out there - each with a slightly different character. This is why you have to do so many plug checks to get it right. “Right” can be affected heavily by the altitude where you ride, the temperature, the humidity, phase of the moon (just kidding about that one)….

There are a lot of different variables. You got to do this right or your pipe will cost you power, pollute more and maybe even hurt the motor.

If you are done riding for the year in the Greater Philadelphia area you just about *have to* do the following:

1. Treat the fuel. Get some Stabil or other brand of fuel stabilizer. We sell Stabil but so do many other places. One ounce of Stabil will treat 2.5 gallons of gas. Pour in the Stabil, fill up the gas tank and go ride it for 20 minutes. This will make sure that you have burned out the untreated gas in the carburetors. If it turns warm and you decide to ride, just replace the treated gas with more when you are done - Add more gas to top off and some Stabil. You want to have the gas tank full. The more air at the top of the tank allows that much more moist air that will result in surface rusting of the inside of your metal tanks.

The gasoline formulations in the Philadelphia area have apparently had fuel stabilizers removed or fundamentally changed some time ago and we are seeing low speed jet clogging in as few as four weeks. The low speed jets are the smallest and clog the easiest. “Running the bike hard” after clogging rarely clears them out. There isn’t enough vacuum to do it. This will be the traditional “it runs on the choke but won’t idle” scenario.

This does not appear to be a brand specific problem and we are seeing this on a number of manufacturer’s bikes. IOW, it seems to be the gas not the bikes. The ethanol (alcohol) is apparently also bringing in moisture from the ambient air and this is causing problems with some float needles. Some have corroded in place in the float seats and we had to pull some needles out with tools to free them. That is pretty serious for your average float needle! Stabil or some other stabilizer is the best action we can recommend.

2. Charge the battery once a month and don’t let it freeze. Consider purchasing a Battery Tender and use it. The Battery Tenders are “smart chargers” and do not constantly charge the battery. They are designed not to boil off the water and overcharge the battery. When connected they do, however, constantly monitor the state of the battery and top it off when needed. They then go back to monitor mode until the battery sinks down enough to require a light charge again. They charge at a very low amperage but they have nothing else but time so the rate of charge doesn’t really matter.

3. Starting the bike up every so often is ok, but run it long enough to warm up the oil throughly. If you are not using a battery tender starting,  but not running, will really take the battery down. Batteries will charge at idle on most bikes but starting will take quite a bit of energy out of the battery in the winter. If you do start your bike ride it if you can or run it for a while.

Please do these things at least (call us if you want to discuss other things to do) so we don’t have to see you right away in the spring!