Wednesday, June 5, 2013

Ninja 250: Battery Health

Its inevitable that the battery on a motorcycle will eventually fail. But what isn't so obvious is how they fail. A motorcycle battery is a fickle thing. One minute it can be working fine and the next it doesn't have enough power to run the dash lights.

One common failure mode is that the bike will crank just fine, but not start. While a no-start condition can be caused by a multitude of things, a bad battery is one of them. The reason is because the bike's ECU requires a minimum of about 9 volts to operate. Below that, you wont get any spark. When you press the starter button, there can be enough current to crank the engine, but the process of cranking drops the voltage below 9 volts causing the ECU to fail and results in a no spark condition.

Jumping and Charging

The bike can be started by jumping the battery to another vehicle or by using a self contained jump starter device. When using another vehicle, that vehicle's engine should be turned off. The higher voltage of the car (which is charging at 50-100 amps) can damage the diodes in the voltage regulator circuit on the bike.

This is true even when the ignition is off. So when charging the motorcycle battery with anything bigger than a trickle charger, the battery should be disconnected from the bike or the main 30A fuse should be pulled.

Push Starting

Push starting is a bit tricky with a Ninja. Chances are, when you last turned off the bike, you had the transmission in first or neutral. Because the Ninja has a Positive Neutral Finder, you cannot shift it to a higher gear and a higher gear is necessary for push starting.

But before you attempt to push start your bike, make sure that you at least have enough current to run the dash lights. Remember that the ECU needs at least 9 volts. If the dash lights don't come on, then you can push it to the moon and back and still not get it to start.

The first step is to get the bike into a higher gear. You need to get the bike rolling before you can shift to a higher gear. Pull the clutch in and start pushing the bike. After it starts rolling a bit, you can pop it into high gear.

But don't stop. Now that you are rolling in high gear, turn the ignition on and let out the clutch. If its going to start, this will be the time. Be prepared to pull the clutch and apply the brakes as soon as it starts. Remember that you are now in high gear and you need to put it back into first or else when you try to take off, you will stall out again.

Testing the Battery

With a voltmeter you can tell a lot about the condition of your battery. A total of four measurements need to be taken - key off, key on, cranking, and running. The basic procedure is this:
 
  1. Turn the key off and measure the battery voltage. It should be higher than 12.5V.
  2. Turn the key on - should be higher than 12.1V.
  3. Press the starter button and measure while the engine is cranking. It should not go below 9V (preferably not below 10.0V).
  4. After the bike starts, measure the running voltage . This should be higher than 13.5V.

In most cases, a bad battery will fail at least one of the above tests.

Battery Size

Depending on your model year, your Ninja takes one of three battery sizes.

The Pregen (1988-2007) takes a 7L-BS battery. It measures approximately 4.5” x 2.8” x 5.2" and has the positive on the right looking at it with the terminals closest to you.

The 2008 Newgen was an odd year and it takes a 7A-BS which measures approximately 5.9” x 3.3” x 3.7” and has the positive on the left.

Other Newgens take a 9-BS battery that measures approximately 6” x 3.5” x 4.25” and also has the positive on the left.

The Pregen can also take a 12A-A battery if you remove the rubber insert in the battery tray. The dimensions of this battery are approximately 5.3" x 3.2" x 6.3" with the positive on the left. The problem is that this battery is only available as a wet battery.

Shorai makes a Lithium version LFX14A2-BS12 that has 14 amps and measures approximately 4.5” x 2.3” x 3.5” with the positive on the left. This is a near drop in replacement for the Newgens. On the Pregens, it requires the rubber battery tray to be removed. Because the battery is smaller than the original, it may require foam padding to make it fit right.

Battery Chemistry

That being said, I am not a fan of lithium (LiFe) batteries. While I have not had any experience specifically with Shorai batteries, I have used other LiFe batteries on my Ninja and they only lasted about a month before they were totally useless. Others have reported similar problems and also problems with the batteries not working at temperatures less than 50F.

But one thing for sure about LiFe batteries is that they are incredibly light for the amount of power they produce. If being lightweight is critically important to you, then a LiFe battery is the way to go.

The most practical battery chemistry these days is AGM. These are far less expensive than the LiFe batteries and usually last longer.

A wet battery is something that brings back bad memories. The electrolyte is literally a liquid acid that can spill out if you tilt the battery. If it gets on your jeans, it will eat a hole in them. If it gets on your skin, it will eat a hole in that too. They used to be the only kind of battery available, but they are generally something to be avoided now.

Every now and then I see a gel cell battery sold for the Ninja. They are usually more expensive and I can't quite seem to figure out what, if any, advantages they have over an AGM battery. The only thing I can think of is that motorcycle AGM batteries usually require the purchaser to add the supplied acid to the battery and charge it before use. Whereas the gel battery comes ready to go. Its not worth the extra expense in my opinion.

Manufacturers

There are lots of battery manufacturers out there. Most of them will work just fine - its just a question of longevity. YUASA is a pretty good one. For better or worse, I ended up getting the lifetime warranty battery at Cycle Gear. Its a junk battery with a good warranty. I've replaced it several times and they always have one in stock and there is no charge for a replacement. If most of your riding is near a Cycle Gear store, then the lifetime warranty battery will do fine, but if you ride very far from the local Cycle Gear you might prefer a better battery like the Yuasa.



Tuesday, June 4, 2013

Ninja 250: Petcock Problems

The petcock's job is to control the flow of gasoline from the tank to the carburetors. The gas in the tank flows by gravity so even after the engine is turned off, the gas will continue to flow unless something stops it. On motorcycles of yesteryear, the petcock was simply a valve that the rider had to remember to turn off after every ride. On newer bikes like the Ninja, a vacuum diaphragm is used to stop the flow of gas when the engine is not running.

The knob settings on the Pregen (1988-2007) petcock are: OFF, ON, and RESERVE. The OFF setting will shut the flow off completely regardless of the engine running status. There are two intake ports on the Pregen petcock. One is higher than the other. The purpose of this is to provide reserve fuel that is hopefully enough to get to the nearest gas station. The ON selection takes gas from the upper intake. RESERVE takes gas from the lower intake. Both ON and RESERVE require a vacuum from the engine to allow any gas to flow.

The Newgen (2008-2012) has only one pickup at the bottom. The knob settings are: OFF, ON and PRIME. The PRIME selection is a special selection that bypasses the vacuum cutoff and allows gas to free flow regardless of engine run status. PRIME is used to prime the carburetors if they are dry. You should not run the bike when set to PRIME. The ON and OFF selections work the same as the Newgen. There is no RESERVE selection on a Newgen.

Symptoms of a Bad Petcock

The most common symptom is fuel dripping from the carburetors or the crankcase filling up with gas. This is caused when the petcock fails to shut off the gas when the engine is off. This can be caused by several things. The diaphragm o-ring could be bad or the spring that pushes it into its valve seat could be weak. Sometimes the diaphragm itself could be bad allowing gas to leak through the vacuum port and into the carburetor.

A less common failure is when the petcock becomes clogged somehow and the gas wont flow at all or at a reduced rate. This will cause a no-start condition, a poor running condition or a situation where the bike starts fine, but then stalls a few minutes later. The clog can be anywhere from the intake ports to the vacuum port.

The diaphragm itself is a very thin membrane that can tear easily. When it goes bad, gas can be sucked into the vacuum line to the carburetor, or you could also see gas dripping from the petcock body.

In some cases, the rubber gasket under the knob can wear out. When this happens, the knob selections can operate incorrectly such as the ON position drawing gas from the RESERVE intake port or the OFF position allowing the gas to flow.

Caution

If the petcock has allowed gas to run into the crankcase, then you should not run the engine until you have repaired the petcock and changed the oil. Gasoline is a very poor lubricant and your engine could be damaged if you run it that way.

Testing the Petcock

To test the petcock to see if it is operating correctly, you can do the following procedure:

  1. Turn petcock to ON (with plenty of fuel in tank).
  2. Remove big hose. Gas should NOT come out - except for maybe a few drops that might be in the hose. There should be no continuous drip, but have a glass jar handy to catch any gas just in case.
  3. Remove the small hose. There should be absolutely no gas come out of the small hose and port - not even a drop.
  4. Attach a 3/16" diameter test hose, about two feet long, to the small petcock port.
  5. With your mouth (or syringe if you have one), apply suction to the small tube (again, there should be no gas in the small tube). Gas should flow out of the big tube in a nice thick stream.
  6. Stop applying suction. The gas should cut off.
  7. For Pregens, switch to RESERVE and repeat the test.
  8. The gas that comes out should be free from any debris. If its clear, you can pour it back into the tank.
  9. Lastly, switch to OFF and apply suction to the small tube. This time there should be no gas come out.
If the petcock does not operate as described, then you need to remove it and repair it.

Rebuilding

If your petcock is bad, you can either rebuild it or buy a new one. I don't recommend buying used ones because they could be just as bad as the one you are replacing. If you rebuild, be advised that the parts aren't cheap.

There are some rebuild kits out there, but generally, its cheaper to buy just the parts you need from the dealer. Be advised that the Oldgen (1986-1987) used a different diaphragm so rebuild kits for it will not work with the Pregen (1988-2006).

Whatever you do, don't be tempted to use RTV to seal any part of the petcock. RTV is not gasoline resistant and will clog up the works and/or leak.

Finally, if you remove the petcock from the gas tank to rebuild it, be advised that the washers on the bolts that go into the tank are special washers that have been coated with a special gasoline proof rubber. These are sometimes not reusable and should be replaced. If you replace them with hardware store washers, expect them to leak. The main petcock gasket is usually reusable, but occasionally, it has to be replaced as well.




Monday, June 3, 2013

Ninja 250: Overtorquing the rocker arm locknuts


There have been too many Ninja 250 owners do their own valve adjustments and then end up having to buy a new engine as a result. The problem is that they are overtorquing their rocker arm locknuts.

Here is a photo of a new rocker arm and a worn out rocker arm:

The larger nut on the end is the locknut. To adjust the valves, you have to loosen that and then use a screwdriver to turn the smaller screw inside the nut in and out. Then, to keep the adjustment screw from moving, the locknut is tightened back down.

It is when this locknut is tightened is where some people overtorque it and end up destroying the entire engine.
At first glance, someone might conclude that the worst thing that could happen is that you'd need to buy a new nut or perhaps, at worst, a new rocker arm. But in reality, its more like lighting the fuse to a nuclear bomb.

Overtorquing the rocker arm locknuts starts a chain reaction that ends with the total destruction of your engine.

The first thing that happens is that one of the the little dog ears on the rocker arm is snapped off due to the excessive torque on the locknut. There isn't much too them, and its easy to see how they can break.

 
There should be two dog ears on the rocker - one on both sides. The dog ears are what keep the rocker from coming loose inside the engine. The rockers do not have hinges or retainer pins like they do in some cars so once one of the dog ears breaks off, they are free to come loose.

The next thing that happens is that the loose rocker arm bounces around until it finds its way down the cam chain tunnel. There is really only one place to go at this point - straight into the crank's cam sprocket. What happens is that the loose rocker gets jammed between the chain and the sprocket.

Now when the crank rotates around with the rocker under the chain, it does several things. First, it breaks off a cam chain retainer that is molded into the engine block. Second, it causes the chain to skip several teeth on the sprocket resulting in a major valve timing error.

The Ninja 250 engine is known as an "interference" engine. This means that the valves and pistons take up the same space, but at different times. So as long as the engine valve timing is correct, the piston and valves never hit.

But when the valve timing is off, the pistons will hit the valves with enormous force. This causes several bad things to happen. The most common is that the remaining 7 rocker arms are broken in half.

If you are lucky, then that is the end of the damage. But if not, other things that happen are bent rods, bent valves, broken cam bearing blocks, cracked pistons and cracked engine blocks.

But now, instead of just one rocker wreaking havok in your engine, now you have 14 half rockers doing the same thing. At this time, the engine is not running, but is still spinning - so the little half rockers are going to make their presence known. If any of them get stuck between any gears in the engine, and there are a lot of them, then those gears are toast.

So anyway, I hope this explains why overtorquing the rocker arm locknuts is so bad.