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Fuel lines for a 912 ?

in 912 / 914 Technical Questions 12 years ago

  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hello Roger

    We are in Western Australia. We did a 5 Year rubber changeover about six months ago. A month or so later we some flaking of the rubber lines going to the Carbs. Showed up with a bit of rough running. The lines were changed over.
    Last Saturday we had very rough running with large flakes in the fuel bowls. We pulled off the pressure hose from the pump and this was deteriorated badly with the inner layer bits oozing away from the next layer. The hose was a 30R9, the injection type. The Rotax distributor is recommending 30R7 (or the 09) sourced locally. We can't find a Rotax recommendation anywhere. We use Premium Unleaded 98.
    The flaking is concerning for us on reasonably new line. Our investigations are continuing. Any ideas?
      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hi Stewart,

    This has been a hot topic of late. Here are some of the reasons for issues.
    Most common is poor installation technique. This is an education problem and not a hose problem. If you use fuel injection hose it has less give than standard carburetor hose because the FI hose has a higher pressure rating. So if you push the FI hose dry over a hose barb there is a chance to scrape the inner lining of the hose and send particles down stream. This has been an issue for some as of late. If you use too much clamp pressure it can cut the inner liner of the hose with a barbed fitting. If you push fuel hose through fire sleeve it can accumulate garbage in the end of the hose. It really needs to be blown out. If you use serrated scissors or something along that line you can get very small flecks of hose hanging there and when you push the hose over the fitting they break off and head downstream.
    The number one cause for hose debris is mechanical damage from installation. It isn't quite as easy as yanking off the old hose, shoving a new one on and clamping it with any old clamp with any amount of pressure you want to exert on it.

    The last reason is there have been some bad sections of hose floating around and from no one in particular. The best way to check is pull the suspect hose off. Split it down the middle. If the hose is trash in the midsection probably bad hose. If it is trashed by the fitting most likely mechanical damage.

    You may have had one or both of these. Replace the hose. I prefer standard carburetor hose over Fuel injection. The standard carb hose has a little more give and far less likely to scrape the inner liner, but you can still have issues if you don't take care with the install. I also prefer Gates Barricade Greenshield Technology fuel hose. It has a far better rating than a lot of the old standard hoses. I have done a bunch of hose changes and not a single issue with this hose.

    The last thing that may help some find problems before they show up and after the hose change.Is to run the engine on the ground for 30 min. at 3500-4500 rpm. Then shut down and pull the carb bowls and filters. This may help find any mechanical damage debris that made it to the carbs, fuel filter and or your gascolator, but won't help if the hose just goes bad months later. To my knowledge Rotax does use Gates, but FI hose and I'm not sure if it is Gates Barricade Greenshield hose. It can handle all the ethanol you want to throw it at. :ohmy:

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Roger,

    Other than making a neater looking installation, are there any reasons that the oetiker clamps originally installed on the fuel lines are preferable to screw type clamps?

    Bill.
      
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  • Re: Fuel lines for a 912 ?

    by » 12 years ago

    Hi Bill,

    Depending on which screw clamp we are talking about, there is an absolute difference. If you are comparing to the worm drive clamps with the serrated openings the Oetiker are far and above preferable. Even though people think those worm drive clamps work well they do not seal well in a 360 degree circumference, they can cut into the hose and they can over cam with the screw and then become loose and they can be tampered with. I have seen some of them ooze under a little pressure.
    The fuel injection clamp is much better than the one we just talked about. It has the nut on the other end. You can pick these up at most auto supply stores. It gives good circumference pressure, can't over cam, isn't open any where in the middle to cut into the hose, it can be over tightened and could be tampered with.
    That said this is not a bad clamp compared to others. I see this clamp on many oil lines. If you don't over tighten it it is a good clamp. Too many people try to over tighten clamps.

    The Oetiker needs to have the proper size picked. There are different types of Oetiker clamps. (let's talk about the one ear stepless clamp) I do use this particular clamp. It is quick and easy to use. Just squeeze it all the way down, it is tamper proof, has excellent 360 degree pressure and doesn't cut into the hose and it can't over cam and won't loosen. It takes the guess work out of the clamp pressure providing you used the right size which isn't too hard to do.

    I use them on every hose change or anything to do with fuel lines. If someone comes in with the cheap worm drive





    screw clamps I replace them during a hose change. They come in all sizes. I use a Dremel tool with a re-enforced cut off blade to remove them which is fast and easy. You can also use the pinch pliers that crimps them to remove them.
    Fuelinjectionandserratedclamp.JPG (You do not have access to download this file.)
    Oetikerclampkit.jpg (You do not have access to download this file.)
    Oetikerpinchpliers.jpg (You do not have access to download this file.)

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell

    Thank you said by: Jose Juntas
      
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