DIY! How to Removed and Do the Effective Maintenance of the Spark Plug in the GPZ NINJA System

How to

Spark plug is sensitive, so be careful. Air blowing in GPZ NINJA system version that you should definitely do before removing the plug.

If the carburetor is not set, or the electrode is worn out due to too much mileage, the spark plug will not be able to perform its original performance, and replacement is required. Spark plug replacement is one of the basic maintenance items, but if you make a mistake in the procedure, it can cause serious trouble, such as damaging the screw thread of the spark plug and dropping the garbage into the combustion chamber. Before inserting the spark plug wrench, it is important to remove the dirt by paying attention to the tightening area.

Gravel and moisture around the spark plug can cause trouble

On top of the KAWASAKI GPZ1000RX, the cylinder head is an intake pipe connected to the air cleaner case. Certainly, a large fuel tank must be removed before removing the pipe. Even the models in the middle '80s, parts have already been installed and modern super sports have a more complicated structure. Finding a spark plug is just one part of the job, but since it is a key part of the engine, it is not possible to leave it alone without checking.

The electric spark from the spark plug is the catalyst for explosive combustion of the combustion chamber mixture. It is an important part of the engine because the spark which sparks at the ignition timing is large, and the longer the spark flies, the larger the combustion. The electrodes in the spark plug wear out is by creating the sparks, so after a period of use, they need to be replaced.

The mounting position of the plug varies depending on the type of engine, but in the case of a water-cooled 4-stroke engine, the plug mounting part is often in a deep place of the cylinder head. In the case of air cooling, even though it is not enough to say the back of the hole, there are many cooling fins lined up around the plug.

Due to this structure, there are examples of gravel and pebbles that have been splashed around the spark plug, and the water that is splashed during the rainy ride or in motorcycle washing will adhere. Even if water adheres, it dries by heat during riding, but sand and pebbles that do not evaporate will remain, and if the spark plug is loosened as it is, there is a risk that the surrounding gravel will fall into the combustion chamber through the screw hole of the plug. Even if the pebbles do not fall, it adheres to the female screw of the cylinder head, and bite into the screw when attaching a new plug, and it causes damage to the female screw.

To avoid these problems, be sure to clean the spark plug hole before unplugging the spark plug. Brushing around the spark plug with a brush that has a thin tip like a common brush, and blowing it off with the air from the compressor but a foot-operated inflator equipped with a needle-shaped adapter for inflating the rubber ball can also be used.


  1. The screw area around the spark plug is dirty with gravel and pebbles.
  2. It is important to air blow before loosening the spark plug to prevent screw troubles.

Deep spark plug hole should be careful of rainwater flooding

The GPZ900R NINJA engine, which has a camshaft chain tunnel on the left side of the motorcycle that lowers when parked on the side-stand, has a camshaft chain cover that looks like an embankment and stops the water on the top of the cover. Water accumulates around the spark plug when the surface of the water exceeds the spark plug hole of the first cylinder.

Since this trouble is like a chronic disease of the NINJA system, the seal is attached to the spark plug to prevent water ingress from the manufacturer of the parts, and the spark plug cap with a taller part is even available on the market.

The oil flows into the spark plug hole by the deterioration of the gasket of the head cover is trouble peculiar to a NINJA engine, which can occur mainly not just the first in any spark plug. If the spark plug cap is clingy with oil, the head cover gasket needs to be replaced.

In the case of a water-cooled engine with a deep spark plug hole, there is a problem that it is difficult to get out of the water accumulated in the spark plug hole. The water around the spark plug is easy to evaporate because the surface of the engine under operation is considerably hot if it is an air-cooled engine, but the water-cooled engine where the cooling water is circulating may not become extremely hot in the vicinity of the plug hole.

In addition, in the case of a motorcycle that is stored outdoor without the body cover, the rain that wet the cylinder head may penetrate through the spark plug hole. Some engines are equipped by a spark plug cap with a waterproof function, but if the seal performance is reduced due to the heat and aging of the engine, it is impossible to prevent penetration.

In the case of KAWASAKI GPZ1000RX which introduce here, the engine is a side camshaft chain type derived from GPZ900R NINJA, and the camshaft chain is installed to the left of the first cylinder. That is why the left end of the cylinder head cover is as high as the embankment, and if you are parked at the side stand, the water on the head cover will gather here. Therefore, it is not unusual that the metal fitting part rusts red only by the first spark plug.

Furthermore, as a standard problem with the NINJA engines, there is a case where engine oil that lubricates the head flows into the spark plug hole due to the deterioration of the sealing performance of the spark plug hole gasket of the head cover. Rust may be prevented if oil adheres, but certainly, there is no reason to remove the spark plug as it is.

In the case of this RX, although there was no water infiltration, the engine oil was flowing into the spark plug hole due to the deterioration of the gasket, and the oil must be removed before removing the spark plug.


  1. Engines with deep spark plug hole are at risk of flooding in outdoor storage.
  2. Be careful of oil inflow in the GPZ900R NINJA series engine!

Air blowing is effective after covering with a waste cloth

If you look into the spark plug hole, it's so deep that you can't see it at all, so the spark plug socket is used as a dipstick to check the amount of oil by inserting it into the enigne. Fortunately, the only one that had oil flowing in was the other spark plug hole. At this stage, I still hadn't loosened the spark plug, so I haven't set the ratchet handle at the base of the extension bar.

About 5mm is wet from the tip of the socket, and you can see that the oil is soaked up to this point. If water accumulates in the spark plug hole, a leak may occur from the spark plug cap depending on the amount of water, causing the spark plug to misfire, but it is difficult to understand the problem because it does not misfire when it is an oil leak.

Whether oil is accumulated in the spark plug hole, it can be determined by the oil content to the spark plug cap. If you wipe the removed spark plug cap with a waste cloth and use oil to make it slippery, you need to replace the gasket.

This engine has been made that the spark plug cap was smooth with oil, and because the oil adhered to the tip of the spark plug wrench inserted for confirmation, and there was an oil reservoir around the spark plug.

To remove the oil before removing the spark plug, there is a method to push in a thin strip of waste cloth into the spark plug hole and suck it up little by little, but if there are a compressor and an air blow gun, it is faster to blow it with the power of the air compressor. At this time, if the inlet of the spark plug hole is covered with a waste cloth, the oil spouted from the bottom of the hole, and it will not pollute the surrounding area.

The point is to air blow with the spark plug hole covered with a waste cloth so that the surrounding area will not be contaminated with the sprayed oil. If you blow air after spraying the parts cleaner, the dirt removal will be even better.

In the waste cloth not only the oil is spouted out of the spark plug hole, but also the dirt inside the spark plug hole. The spark plug cap is sealed, but it is not possible to get dirty because the air tightness is not high. On the flip side, even if there is no water or oil, air blow after removing the seal-type spark plug cap is essential.

In addition, if the spark plug hole is not possible to clean it once, it is possible to wash it effectively by spraying the part cleaner in the plug hole and air blowing. In the case of a motorcycle with a sealed type spark plug cap, it is rare for gravel or foreign matter to enter the spark plug hole, but cleaning in advance with parts cleaner + air blow is also effective for air-cooled engines.

If you prepare this far before removing the spark plug, you should be able to reduce the risk of dropping foreign matter into the combustion chamber and damaging the female thread.

When installing a new spark plug, it is basically necessary to pick it up with your fingers and turn it until the screws are firmly engaged, but for engines with deep plug holes, you may be forced to use a spark plug wrench from the beginning. In this case, the spark plug is carried perpendicular to the screw hole, and it does not gain momentum to the spark plug wrench, and it rotates slowly until the screw engages.

Unlike normal bolt and nuts, damaging the screw holes in the spark plug requires major repair of the cylinder head. Don't underestimate the importance of preparation before loosening the spark plug.

The bracket part of the removed spark plug is dirty of sticky with emulsified oil. What I can determine from this is that there was a mixture of oil and water in this spark plug hole. If only water enters and the spark plug rusts, it may break when it is removed and may not come out. If that happens, it will take a lot of effort into the extraction work, so it may have been unfortunate that there was oil.


  1. The oil inflow into the spark plug hole is determined by the dirt in the spark plug cap.
  2. To remove oil stains, spark plug the spark plug hole with a waste cloth and blow air.
  3. Cleaning before loosening the spark plug will protect the cylinder head from wearing out.

See KAWASAKI Moto Index Page
See Accessories for KAWASAKI GPZ1000RX (Ninja1000R)
See Accessories for KAWASAKI GPZ900R Ninja

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