Honda CB125

The fuel strainer and bowl are integrated into the fuel tap to provide reasonably efficient filtration of the fuel. The bowl also seperates water from the fuel fairly effectively. Honda suggests that the fuel strainer and bowl are cleaned at 4000km intervals but this figure is dependant on the quality of the fuel that is available to you. In localities where the fuel is of a high standard 4000km is probably too frequent, in locations where the fuel is of poor quality shorter intervals may be necessary. I suggest using your own experience as a guide. If the bowl and strainer are spotless the first time you clean it and you always get your fuel from the same source you might consider a longer interval to avoid unnecessary wear and tear on the fuel bowl thread and o-ring.

Although removing and replacing the fuel bowl, fuel strainer and the o-ring is a simple task it is something I dont perform on my own CB125E as often as Honda suggests. The fuel I use is nothing short of excellent and I have never seen so much as a speck of rust in the fuel strainer in the several times I have inspected it. As a result it is on my 12000km inspection schedule instead of the recommended 4000km. That is probably a way longer interval than is wise but there is a reason for this. I have been maintaining motorcycles for over thirty years and the number of these bowls I have seen with crossed threads is not small. The fuel bowl and fuel tap body is die cast and soft, very very soft. The threads appear to be rolled, at least on the fuel bowl. This is not a bad thing but it is a potential disaster if you cross thread it. If you attempt to repair the thread it will probably simply fall off. Overtighten it and you will destroy the o-ring and once again risk damaging the thread. To top it off the bowl is a standard clockwise tightening thread but it is 'upside down' so to speak due to its location on the bottom of the fuel tap. I think this is where new players have problems, tightening it instead of loosening it. The soft materials also introduce the possibility of slowly wearing the thread out every time it is removed and replaced, which is why I dont like interfering with it unnecessarily.

So we can see that the potential for a fuel leak is fairly high if the fuel bowl is not removed and replaced with care. Take your time on this easy little task and you wont encounter any problems. If you have a doubt get help from a mechanic or a mechanically minded person.

Start by turning the fuel tap into the OFF position. To remove the fuel bowl and fuel strainer first locate the bowl on the bottom of the fuel tap. You will notice that the fuel bowl has a nut cast on its base. Put a spanner on this and loosen it by turning it in the normal direction for a standard thread. It should loosen quite readily and then be easily be removed by hand. Be careful to keep it upright as the fuel bowl will contain petrol, be careful not to spill it everywhere and make sure you do not get any in your eyes. The fuel strainer and o-ring may also come out when the fuel bowl is removed. Have a quick look at the contents of the fuel bowl, is it 100% fuel or is there rust and/or water? The contents of the fuel bowl and the quantity of trapped particles in the fuel strainer will give you a useful guide to the quality of the fuel you are getting as well as the condition of your fuel tank.

The o-ring and strainer can then be removed if they did not come out with the bowl. Make a note of which way up the o-ring was as it must go in right way up. Usually the o-ring will hold the strainer in the fuel tap body like you can see in the adjacent image. Gently remove the o-ring taking great care not to damage it and then the fuel strainer. Clean all of these items with low pressure compressed air, say 20psi or you can even blow them out with your own breath.

Putting it all back together is the exact oposite of pulling it apart. Put the fuel strainer in first making sure that it sits properly, the inlet hole is offset and the fuel inlet in the body of the fuel tap must go into this hole. The o-ring is flat on one side and curved on the other to make it a good fit onto the fuel bowl (curved side) and fuel strainer (flat side). Install this next and you will find you can use it to hold the fuel strainer inside the fuel tap body. Make sure that the o-ring is sitting flat and square inside the fuel tap body and is right side up.

Finally, carefully screw the fuel bowl back on by hand until you can feel it make contact with the o-ring. It will become harder to turn when you feel it touch. Turn the bowl about 1/3 of a turn further with your spanner. It should feel fairly firm. Turn the fuel tap on and see if it leaks. If it doesnt then it has sealed adequately. If it does leak tighten it slightly more, say another 1/3 of a turn and see if it then seals. If you overtighten the fuel bowl you will flatten or damage the o-ring in the very least. You may also damage the thread as previously discussed. The objective here is to tighten it enough so that it will not loosen and a 100% seal is obtained. If you tighten it to the point where it becomes hard and it still leaks then you should take it all apart again and try and determine what is wrong. Once you have tightened it to the point where it seals keep an eye on it for a few days to make sure it does not leak.