Googling around for “CBF 125 Kangaroo Problem” will give you many results. It is one of the most annoying and potentially dangerous problems with the little CBF (more details here), and since it happened to me 3 or 4 times I was fed up and made it my mission to actually find a solution.
I googled vigorously, first to find the cause of the problem, and second, to find a solution.
Now, I don’t know much about motorcycles, engines and stuff like that. I’m a computer guy but the solution seemed to also fit with the cause I was able to decrypt from my research so that’s what I went with.
What seems to happen is that on hot days (where the problem seems to manifest most), the combined heat from the engine and from the outside world, kind of “boils” (for lack of a better word) the fuel causing the engine to stutter, as it is running lean. This also overheats it more and so the cycle continues…
I know that may sound idiotic (keep in mind, I’m not a mechanic) but hear me out.
You’d think that Honda would have accounted for that, or you could say: “Why isn’t that a problem in all other motorcycles?”.
What I found out is that most motorcycles have a layer of insulation between the bottom of the tank and the engine. That at least keeps the accumulated heat in the area, during little to no movement (traffic), from the fuel.
Honda, on the other hand, skipped this for the CBF 125, possibly to reduce manufacturing cost.
Having read that and realizing it’s the most likely cause of the problem, I made a trip to my mechanic.
What my mechanic told me was that this (putting an insulating layer between the tank and the engine) was actually what Honda had told them to do if a bike needed more than 3 pump changes during the warranty period. So they knew the problem existed at least, and they knew why.
I had him put one in immediately and I’m happy to say that it’s been a year since and I’ve had zero problems with the bike. I was able to test it in very hot weather and in very heavy traffic and the bike just keeps on going without a hitch.
My explanation may be crude but I think this (or something similar to this) is what is actually happening.
I haven’t googled the problem since last year, so I don’t know if this is actually a widely know solution to the problem or if I’m the first one to point it out (probably not), but this blog is pretty well known, and I though I’d contribute so more people can know.
Have your mechanic put in an insulation layer between the bottom of the tank and the engine.