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Your Motorcycle: The Enemy Within.

January 9, 2017

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How to Avoid Very Expensive Motorcycle Repairs Pt 1

January 12, 2017

You jump on your bike (or in your car), twist the key on and press the start button. The engine turns over but it refuses to start. You try again and again and nada. A lump forms in your throat as you try to sort out what is going on?

 

What does an engine need to start?

 

Doesn't matter a motorcycle engine or a car engine. An engine needs 3 major ingredients to start. It needs compression which goes to the condition of the engine itself regarding, pistons, rings, valves, head gaskets and even a loose spark plug. 

Except for perhaps a loose spark plug this is usually a given unless you heard some weird sounds coming from your engine the last time you road it. If you have compression the next thing you need is spark to your spark plug. This is to ignite the fuel gas mixture that was drawn into the engine and compressed. To have something to burn you also need fuel. If you are out of gas you can have the two above named elements but the motor will not start.

 

But what if you have plenty of gas and it still won't start, what then? You have to determine which one is missing and then proceed to trouble shoot that part of the system. You start with the easiest and cheapest tests and proceed with the more complex ones. In a fuel injected motorcycle bike, when you turn the key on you should hear the pump hum from the gas tank for about 3 seconds and shut off. If you don't hear it that could be why the bike is not starting. You either burnt a fuse or burned out the pump. If it is the fuse consider that a warning as it is not normal. The pump is drawing more current because it is about to fail. If the fuse fails to restore the humming sound of he pump then proceed as follows.

 

The easiest way to sort this out is to buy a can of starting fluid from one of the auto parts stores. Buy the one with lubricant as this is not gas but is ether a volatile fuel that strips oil away from the engines internals. You have to do a bit of digging but you want to spray this stuff in the air intake of the bike or through the air cleaner. The latter maybe buried in your bike. An engine has to breathe and their are external ports where you can spray the ether in. You want to have your key in the ignition ready to start and just spray a bit about one second, anymore and you can have a backfire. Spray, start and if the engine runs for a second you have a fuel problem. Spray start and if nothing happens repeatedly then you have a spark (ignition) problem and perhaps a fuel problem. You have to remedied one issue at a time ideally. This procedure can be used on any bike or car.

 

Today, we are going to look at a common failure modality in electronic fuel injection systems EFI for short. They are in the bigger picture complex systems in comparison to their carbureted cousins and but as you slice and dice the systems the smaller components actually have very simple and logical functions that are easy to understand. You always approach trouble shooting by examining what are the weak links in the system and more prone to failure. In an EFI that system it  is the fuel pump. Its job is to draw the gas from the tank pump the gas up to a pressure of 40 - 50 PSI and send it through a 10 micron fuel filter to remove tiny contaminates and then it makes its way to your engine to be injected into each cylinder at the appropriate time.

 

I will write articles about the rest of the system in the future for the time being I want to focus on just the pump as this strands more riders than any other item.

 

In many designs the pump is immersed in the tank and is covered and cooled by the fuel. They run at relatively high RPM's and get quite warm from the current flowing through them and the friction in the bearings. As long as you keep them immersed in gas and regularly change the fuel filter they will last for a very long time and that is a good thing because some can run as much as $300 to replace and in cars they can cost almost $500 for OEM to replace and it is a big ass job. On a car, this can cost you between $500 - $1,100 including labor.

 

 

What destroys them is heat and back pressure which causes even more heat. By making sure either on you bike or your car that you keep at least a 1/4 of a tank of gas in it at all times you can assure that it is being cooled sufficiently. Old fuel filters in this micron range which is very fine can quickly get loaded up to the point where the pump gets loaded up and will overheat even when it is fully immersed.

 

With some bikes you can remove the filler cap and observe the fuel pump and even touch it, to sense for excessive heat. If your pump starts popping fuses again that is a warning that something is wrong. Other signs are flat spots under acceleration, which means the engine loses power for a second or hesitates. This is because the pump is not running at high enough rpms or the fuel filter is reducing pressure to the system. As you demand more fuel it does not deliver or has to catch up. Usually within a few weeks or months your riding days are over. But if you are proactive and change the filter you an in some instances buy yourself even more time. If you do get stranded a trick that sometimes works is to take the fuel tank filler cap off usually about 5 Allen screws and reach in and gently tap on the pump while it is keyed on. This can sometimes jar it loose. On a car you would bang on the bottom of the tank while it is keyed on. This trick does not last forever though.  About every 3 years you should pull the pump from the tank and replace the intake bag filter or diaper on the pump as it can cause drop in pressure and damage the pump.

 

So the moral of this story is that an ounce of prevention fuel filters ($15) and keeping the right fuel level will put off expensive repairs far off into the future. 

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