Rotax 912 series oil filter – new service bulletin

Rotax has issued a new mandatory service bulletin covering their oil filters – SB-912-071.

Due to a manufacturing deviation, the sealer gasket on the oil filter may leak, causing possible loss of oil pressure and oil.

If your 912ULS engine number is within the series from S/N 9 569 542 up to S/N 9 569 782 inclusive, or you have service replaced your oil filter since June 2017, you need to check the filter. If it has a green mark in the specified location, the filter is OK. If not, check for leakage and if any is seen, the filter must be replaced immediately. Even if there is no visible leak, the filter must also be replaced immediately on listed engines.

If there is no green mark on the filter, no leakage and the engine is not listed, the filter should be replaced within 25 engine running hours or within 200 days from 01 November 2017, whichever occurs sooner.

Here is a link to the service bulletin which gives full details: SB-912-071
Here is a link to the listed 912UL & 912ULS engines affected: SB-912-071UL

Urgent Rotax safety bulletin

Rotax has issued an urgent and mandatory service bulletin on their 912/914 series engines. It applies to a limited selection of engines built between June 2016 and October 2017 – check your Foxbat/Vixxen 912ULS engine number against the list below to see if you are affected.

(A) from S/N 6 785 971 up to S/N 6 786 198 inclusive
(B) from S/N 6 786 501 up to S/N 6 787 000 inclusive
(C) from S/N 9 569 001 up to S/N 9 569 690 inclusive
(D) from S/N 9 569 693 up to S/N 9 569 702 inclusive
PLUS S/N 9 569 823

In summary
Rotax reports that deviations in the manufacturing process of the valve push-rod assembly may cause partial wear on the rocker arm ball socket. This wear could lead to a rocker arm cracking/fracture which in consequence may lead to a malfunction of the valve train. Possible effects are rough engine running or an unusual engine operating behaviour.

The bulletin requires the removal of the rocker covers of affected engines and an inspection – and if needed, replacement – of the valve pushrods.

In simple terms, if the pushrod ends are a silver-ish colour, they are OK. If they are black they will need to be replaced.

Time frame for completion of the bulletin is:
– either at the next scheduled service
– or if a scheduled service is not due, within the next 25 hours of engine running time
– or if 25 hours running time is not completed, by 30 April 2018 at the latest

Here are links to the Bulletins:
What needs to be done:
Which engines are affected:

If you believe your engine is affected, please contact Bert Flood Imports, the Australia Rotax engine agent, for more information.
Bert Flood Imports phone number is: 03 9735 5655

Auto fuel and Rotax engines

rotax2_1Just recently, I have heard stories of rough running Rotax engines. This has been traced on several occasions to problems with the carburettors. It appears that the plastic floats in the carburettors are slowly dissolving in the fuel, causing them to become porous and cease to float! Equally dangerous, small parts of the floats are breaking off and blocking the carburettor jets. I looked at a couple of these floats and sure enough, they were soft and spongy to the touch and there were tiny pieces of black material in the bottoms of the float bowls.

Rotax recommends the use of unleaded automotive fuel – ‘mogas’ – in their 912 series engines. The fuel must have a minimum 95 octane rating for use in the 100hp 912ULS and 912iS models,.

You can also use 100LL aviation fuel – ‘avgas’ – in your 912 if you have to, but you’ll need to change the oil more frequently to help mitigate the effects of lead build up on the valves and other parts of the engine.

All fuel companies use petroleum blends to increase the octane rating of their fuels. Originally the main octane raising additive was lead but this has been phased out for automotive applications, although lead remains in use for aviation fuel. Significant octane-increasing additives in unleaded fuels include ethanol and toluene, both of which work well but they do have their limitations in some applications.

BP UltimateGenerally, the more ethanol or toluene, the more the octane rating is increased. However, this is not a golden rule and some high octane ‘low aromatic’ fuels – like BP Ultimate 98 – do not contain ethanol and have a low levels of aromatics such as toluene.

Both ethanol and toluene can affect rubber and plastic components in the fuel system. Toluene also has a high carbon content that may lead to sooty spark plugs – so don’t assume that this indicates an overly-rich mixture.

So it seems some unleaded fuels which contain substantial ethanol and/or toluene levels may be having a negative impact on plastic and rubber components in your engine!

Rotax recommends fuel with no alcohol additive for their engines but has approved the use of up to 10% ethanol in fuel. They do not mention toluene anywhere in their technical information. Your airframe manufacturer may or may not have approved the use of ethanol in any proportion. This is important to note, as the fuel tanks, fuel lines and auxiliary pumps they install could be affected.

My feeling? Stick with fuel that has no alcohol and meets at least the minimum required 95 octane for the 912ULS and 912iS engine. The higher the octane, the more likely it is to include higher levels of additives. Certainly, steer clear of any premium unleaded quoted at 100 octane or at least check if it has ethanol in the product. And maybe it’s a good idea to stick with the well known big brand name fuel distributors rather than fuels from an unknown source, that is, until we get more of a handle on the exact nature of the problem. They may be a cent or two more expensive but in my opinion, that’s a small price to pay for some peace of mind!