Possible solution to the dreaded “Kangaroo” problem

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.

The cause

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.

The solution

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.

TL;DR

Have your mechanic put in an insulation layer between the bottom of the tank and the engine.

 

 

 

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10 thoughts on “Possible solution to the dreaded “Kangaroo” problem

  1. Hi I had this problem on 8/5/16 but have also notice that my bike seems to be lacking power sometimes do you think that if I fit the insulation this will resolve the problem as have been debating whether to change the fuel pump.

    • I think it will solve your problem. However, I think that you may also need to change the pump since this problem damages (air passing through instead of liquid).

      If you are under warranty I suggest you do both.

  2. Hi, That’s quite interesting, I hadn’t realised that there was an option of insulation being fitted between the engine and tank.
    What I can tell you, is that you are only addressing half the issue (which hopefully will prevent further occurences). What that heat does is soften/melt the internal lining of the fuel tank. It’s a coating of a type of wax, which is attacked by the ethanol in the fuel, and the resultant sludge will clog your fuel pump (because Honda decided to integrate the fuel filter to the pump).
    What a number of people have done, including myself, is to fit an in-line fuel filter (just search for them on ebay, it’s a couple of quid). The fuel line is behind the left middle fairing, and you’ll need to cut a chunk out of the pipe to fit it. You can get clear one’s, so it’s quite easy to see the sludge being prevented from reaching that pump!
    The combo of the in-line fuel filter and the heat shielding should make your CBF125 bullet proof against the dreaded Kangaroo hop.

  3. That’s interesting reading. I agree the symptoms suggest a problem caused by the excess heat, I never found anything else other than the stories on the wax costing in the tank clogging the fuel pump and heat was the issue/cause on a hot day.
    This happened to me a week ago riding home on my newly purchased CBF125.
    But I have had many bikes and very few have had a reflective lining under the tank so can’t see how it can cause the CBF’s problems but agree that only having half a tank of fuel and slow riding after a constant high speed run cropped up a few times in riders description of the kangarooing fuel pump issue. I spoke to 2 service managers at dealers who knew/remembered the fuel pump fiasco and neither mentioned the reflective lining for heat, only that a new fuel pump fixed the issue(wax in pump).

    • I have already gone through 3 different pumps before that fix, but I think a combination of all these is the real issue.

      As you say, other bikes don’t have the insulation but the cbf125 has an already sensitive pump so the problem appears more often.

      I can’t say that it’s not the other things that cause the issue, but I’m pretty sure all of them combined make for the frequent appearance of the issue.

      Who knows.

  4. Load of Horlicks. The problem is the tank and the stuff they (from the factory) put in the tank to stop it rusting, a good clean of the tank (from new) and a inline fuel filter is the solution.

  5. Hi I have the same problem, and I was thinking about to protect the fuel line from heat all the way up from tank to the pump inclusive the pump , because i think that’s too much heat for the pump and the gasoline, which came from the engine and the outside world.
    Can you please help me what material to use for that? Do u have pictures of the modding?

    Thanks a lot,

    Dorian

    • Exhaust Aluminised Heat Shield Glass Fibre Cloth – 500mm x 500mm wide

      Search that on eBay uk or copy and paste this link

      http://www.ebay.co.uk/itm/Exhaust-Heat-Shield-Aluminised-Glass-Fibre-Cloth-500mm-x-500mm-wide-/111304099165?hash=item19ea3dc55d

      I cut 1″ wide strips and after removing the rear seat, main seat and side panel, I wrapped this heat reflective material around the fuel pipe from the tank to the pump and also the pipe from the fuel pump to the injector. To help make it easier to do, cable tie the start of the wrap to one end of the pipe to hold it in place then wrap the rest of it around the pipe, use a couple more cable ties to hold it all in position.
      Wouldn’t recommend wrapping the fuel pump, it needs good air flow to dissipate heat, if you wrap it in heat reflective matting then it’s own heat can’t escape.
      I wrapped my fuel pipes yesterday so can’t comment on effectiveness yet but vapour lock which is the theory of the fuel vaporising in fuel pipes from too much heat can happen to any vehicle from motorbikes to rally cars. The CBF125 displays the fuel starvation symptoms of vapour lock and clogged fuel pump, both have the same resultant effect. Wrapping the fuel pipes is the usual fix that works. It certainly won’t do any harm to the CBF125 so you have nothing to lose in trying.

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