Due to the fact that the CBF125 has no form of visible filtering for petrol, either in the tank (the only part you can take out of the tank is the fuel level float/sensor) or rest of the system (fuel pump is a sealed, replaceable unit and cannot be disassembled), I, and many others have felt it best to add an in-line filter to the fuel hose running from the tank to the fuel pump.
Here’s my example (as always, click the image for a larger version):
If you want to add one yourself, the following information may be helpful:
- SAFETY FIRST! Petrol, in both vapour and liquid forms is extremely flammable and has a low flash point, hence why a spark can ignigte it! Keep any sources of ignition well away. Petrol vapours aren’t good for your respiratory system either, so make sure you’re working in a well ventilated space. They’re also not good for your skin, so use a barrier cream or appropriate gloves. Also use eye protection because the fuel system on this bike is under pressure so petrol may squirt out at you as you cut the hose! You’re best off clamping the hose near to where it leaves the tank with a proper hose clamp before starting this job.
- The internal diameter of the hose will fit either 6mm or 8mm nozzles on a filter, I have chosen one with 6mm nozzles and have observed no leaks after 120 miles of riding.
- The external diameter of the hose is about 10mm, and the spring clips I have used either side of the filter are for a 10mm hose. They compress the hose around the nozzles because the external diameter of the hose expands slightly over the fittings. If using a filter with 8mm fittings, you may need larger clips, perhaps 11-12mm diameter ones.
- You have about 40-50mm of usable space in the fuel hose for a fuel filter, including its nozzles, but you will have to kink/bend the hose out of shape if fitting a larger/longer filter. This may well over-stress the hose and/or disrupt the flow of fuel, starving the engine, so I do not recommend fitting a filter that is too long.
- Blow through the new filter with your mouth to check its flow – it should be easy to blow through it, feeling a little resistance. Some filters are blocked when they leave the factory, believe it or not!
- Look for an arrow on the filter that indicates the correct direction of flow for fuel, and install it the right way around.
- Don’t forget to inspect/clean the filter at service intervals, or replace it if it’s a disposable one (I’d say after 7’500 miles or if it’s damaged/excessively clogged).
- If you’ve fitted a plastic filter, inspect it after each ride for a few times after you first fit it, looking specifically for melting/warping of the plastic, due to the close proximity of the cylinder head, which gets very hot. It is not unheard of for plastic fuel filters to be damaged by heat, so be vigilant – we don’t want to be going up in a ball of flames now, do we?