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Thread: Rotax 912 carbs overflowing

  1. #11

    Rotax 912 carbs overflowing

    Hi Mike and Dave,
    Reading this thread with interest.

    To recap:
    My Quik trike operated at a max of 0.4 bar with the original (AC) fuel pump fitted. As it has a 912 engine a return bleed off line is optional, and I removed it (as I was thinking of fitting an auxiliary fuel tank system feeding the main tank). Max pressure remained 0.4 bar. This was the quoted rotax max pressure for my engine so in that configuration all was good.

    I then fitted the new rotax fuel pump and fuel pressure increased - normally 0.5 bar, occasionally a little higher. Refitted the bleed off system - no difference to pressure - so max is 0.5 bar or just a little over - which is above the original rotax max fuel pressure for my engine.

    I have made no changes to my carbs and have seen no advice to do so, and to date all seems OK. The engine has 320hrs.

    What is the current rotax max fuel pressure for the 912 series engines?
    Is that pressure applicable to all 912 series engines or just recent ones fitted with the new fuel pumps from manufacture?
    If I should reduce my max fuel pressure to 0.4bar how can I do that (opening the bleed orifice seemed like the only way)

    AndyB

    Edited to add:
    The 'new' pump type is BCP Corona and the Conair web site gives a pressure range for it of 0.15 - 0.5 bar. But no indication if this raised pressure is or is not OK for the carbs on earlier engines.

    Edited again.
    Just had a phone call from Nigel Beale to confirm that 0.5bar is OK with all 912 and 912S carbs - so I think that answers everything.

  2. #12

    Rotax 912 carbs overflowing

    Andy's results above would seem to indicate that either pump has plenty of capacity to feed carbs and an optional return bleed and maintain 0.4bar (AC) and 0.5bar (BCP). So Mike's assertion that opening up the orifice to drop the pressure is not a sound way to proceed would seem correct.

    I will follow this up with the LAA (after the rally) and see what they think.

    Dave

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