Rotax 912 float warning. Check yours. It can happen to you. It has happened to me.

Published by: Paul Hamilton on 28th Apr 2017 | View all blogs by Paul Hamilton

 

Recently, I have had numerous problems with the Rotax Carb Floats. Luckily I was able to avoid an engine failure, just loss of power but enough to land safely. This has been for new and old floats. They absorb fuel and can sink.

 

Some say that the newer floats are OK, Wrong. Some say that the older floats are OK, Wrong. I have seen sinking floats in all ages.

 

It is really simple, run the engine or the electric fuel pump and fill the carb bowls. Pull the bowls and see if the fuel level is equal below the top of the bowl. See if the floats all look like they are floating at the same level and lastly take the floats out, let them dry and weigh them. If a float is more than 3.1 grams it is no good. Rotax sez 7 grams for both, but in my opinion, this does not  leave much room for error.

 

This is a simple safety check for all 912 carb owners

 

Check your floats.

 

Comments

27 Comments

  • Thomas Nielsen
    by Thomas Nielsen 5 months ago
    Thanks for sharing - If your carb floats are absorbing fuel, getting heavy - could that explain why I sometimes only, notice a bit of fuel smell when flying and when checking on ground can see that the overflow tubes have dripped a bit ? I supposedly have the new floats, but that's no guarantee it sounds like. Will definitely ground my Revo until investigated.
  • Paul Hamilton
    by Paul Hamilton 5 months ago
    Thomas, yes as the floats sink it tells the valve to open to let more fuel in raising the level of the fuel and out the vent tubes.
  • Thomas Nielsen
    by Thomas Nielsen 5 months ago
    Thanks Paul ! - I am convinced this is the likely culprit, and that is on a new REVO with the new floats.
  • Paul Hamilton
    by Paul Hamilton 5 months ago
    Long story but new floats there have been significant problems. I new set ordered for a 503 were pealing with the peal getting into the jets. Pitiful at $35 per float. At least it not the crank or pistons :-/
  • Abid Farooqui
    by Abid Farooqui 5 months ago
    Paul H. Please make sure you fill out a CSIR and submit it to Rotax. They need to understand this problem is not over. This was the same problem for Damien in the Delta Jet-2 LITE a few weeks back. Rebuilding the carb was not what was needed. The floats from Bing are defective and still continue to be even after Rotax weighing each one. At an annual they should be checked and weighed. I had a brand new 912 in a gyro with 10 minutes of fuel exposure had floats (1 in each carb bowl) starting to sink very recently. Continental and Lycoming I believe use soldered metal floats.
  • Frank Dempsey
    by Frank Dempsey 5 months ago
    Damien Beresford and I each had an engine out on a 2016 Delta Jet Lite 912 ULS 100 hp just a few weeks ago. The engine only had 90 hours on it. The left float bowl started spitting out fuel intermittently at idle when the engine was warmed up and at idle (i.e. - landing conditions). Damien got a surprise when the engine quit and he couldn't make the runway. He hit flat dirt about200 feet short of the runway in Class D airspace. He declared an emergency and landed it 200 feet short of the runway with no incident. I examined the floats and cleaned the float needle/orifice. It seemed to work but in flying it again, it was cutting out at idle on the down wind. The prop stopped on final about 10 feet up. I sent the carbs to Lockwood in in fact, as Abid guessed, the floats were sinkers. They had cracks at the seems that you couldn't see with a naked eye. The carbs got a 2 year overhaul for $200 and 4 new floats at $80 each. I had to sync the carbs afterwords too. What a pain in the arse this was. Now, it flies like a dream. Frank Dempsey
  • PHILIP QUANTRILL
    by PHILIP QUANTRILL 5 months ago
    Just an idea, if you fully immerse the floats in reasonably warm water if there is a problem with cracks will it not begin to blow bubbles as the pressure inside rises slightly ?? Would of course require careful drying afterwards. Paul, you mentioned a 503, is this problem across the board and not just on 912's ?? If so maybe a change of title may be in order, I have not previously read this thread as I thought it was only the latest carbs effected.
  • Abid Farooqui
    by Abid Farooqui 5 months ago
    The same floats are used in 582. I think may be in 503 as well but not sure. The problem is with floats that are relatively recent starting from 2013/14. But if you had a carb rebuild done the floats may have been changed needlessly as well. It's a materials problem at Bing in Germany. The float is a enclosed foam item but obviously people have been finding fuel in them when they sink. German engineering :)
  • PHILIP QUANTRILL
    by PHILIP QUANTRILL 5 months ago
    Thanks Abid, Bought my trike in 2015 so I'll strip them down and check over
  • wexford air
    by wexford air 5 months ago
    Ya. 503 same as well but as their are no longer any 503 engines produced for the last couple of years there naturally won't be many complaints. Unless someone bought replacements recently
  • Henry Trikelife
    by Henry Trikelife 5 months ago
    We didn't have this issue so frequent before. This happened more frequently in the last few years. This almost looks like to me that Rotax purposely causing this issue, so people think 912iS engine is the better engine ? WRONG !!!!
    I had 3 emergency landings with the brand new 912iS engine.
  • Charles Moore
    by Charles Moore 5 months ago
    I think the question should be why are these very expensive engines so fragile? We've had carb mounting sockets, fuel pumps, cdi ignition boxes (at $1000 a piece) and carb floats. Some of the folks that have been around longer may be able to add to the list. For something that currently retails for $14377 (80 HP model) I expect a little better R&D on their end before sending out a product that is going to have someones backside relying on it while several thousand feet in the air. Chinese made scooters (no offense to the chinese) being ran full throttle stop light to stop light seem to be more reliable. Sorry about the rant. Will be buying a scale and checking my floats this weekend.
  • Thomas Nielsen
    by Thomas Nielsen 5 months ago
    I agree - designing a darn carb float that works shouldn't be beyond the capability of Rotax. I wish a company like Honda would dedicate R/D into an aviation line of small piston engines.
  • PHILIP QUANTRILL
    by PHILIP QUANTRILL 5 months ago
    Maybe there is a good reason many east europeans use BMW
  • Gregg Ludwig
    by Gregg Ludwig 5 months ago
    I really enjoy flying my fuel injected BMW, but when the alternator belt fails the engine will stop in about 30min after the battery goes dead. Actually I've only had one belt failure and it wasn't even that old.
  • Abid Farooqui
    by Abid Farooqui 5 months ago
    Charles: LOL. You forgot the crankcase fretting in engines from 2004 to 2007. Those cannot go to 2000 hour TBO without changing its crankcase. If crankcase fretting happens you are SOL. Search for that on the web and you will see.
    The problem is Rotax (Austrian) uses Bing (German), Bing uses a sub-contractor for floats and carb sockets (also German). The German engineering for production is more a myth of marketing than reality. They have more problems statistically than Asian cars in the last 10 years. The floats have a materials defect. Rotax pointed out where the problem was to Bing and Bing shrugged their shoulders. Rotax makes aircraft engines, its not like every carb manufacturer wants to sell them carbs for aircraft engines.
    912iS roll out was very messy. 912iS is regularly having to change gears at 800 to 1000 hours because of design flaw. When you share engine and gearbox oil and because of fuel injection your fuel mixture is leaner to safe fuel and then you find out the whole engine runs hotter as well because excess fuel was in fact cooling the engine (duh) and that makes the oil and coolant temps go hotter and then the oil in the gearbox does not do its job quite right for too long, well you have to wonder what was so mysterious about that. Everyone knows that already. In short when you allow sales people to make the calls instead of engineers, things go wrong. That's the short of the inside story on 912iS. Also the gear lash had to be changed to get correct crank angle sensor position. I am not sure if 912iS is worth it honestly. It does save some gas but its the same HP, at 18 pounds extra weight with tons of complex wiring and computers. Sounds good but in aircraft we need to "lighten and simplify". If 912iS was 110 HP at the same weight, I'd say great but it isn't.
  • PHILIP QUANTRILL
    by PHILIP QUANTRILL 5 months ago
    Gregg having read the catalogue of errors with Rotax it amazes me that more are not using either BMW or many of the other engines available. Fault after fault appears for a very expensive engine, I understand in the UK, and maybe USA there are rules for nearly everything you do/change , but in countries where the rules are more relaxed, why. When my 582 is nearing the end of its usable life I will be asking the question of Air Creation about changing my mode of propulsion.
  • Paul Hamilton
    by Paul Hamilton 5 months ago
    I used to think it was carb sync but many times it is just bad floats to cure rough running.
  • Ivo Smyly
    by Ivo Smyly 5 months ago
    According to Dean Vogel who works with Phil Lockwood Aviation Group, Rotax now are pressure testing each batch of floats they order from Bing in a vat full of fuel to reduce the percentage of floats that are absorbing fuel, but it continues to be a problem
  • Paul Hamilton
    by Paul Hamilton 5 months ago
    Somehow Rotax is at the top of the pecking order for LSA with the largest market share. Typically this is for a reason and not by chance. I have found the two strokes/four strokes to be incredible reliable if properly taken care of. I now have about 1000 hours on the fuel injected 912iS engine and besides all the incredibly irritating updates/upgrades which I hope I am finally finished with, it is growing on me. No carbs, smoother and much lower fuel burn. I think I am getting better power out of it verses the 912S.
  • Thomas Nielsen
    by Thomas Nielsen 5 months ago
    Had my floats Checked today. Both carbs has been spitting fuel, although intermittent. This is on a 2016 new REVO, currently with 21 hours on it AND equipped with the new floats. One set weighted 7.1 gram and the other side 6.7 grams. In the 6.7 side, one float was 3.7 grams and clearly sitting "deeper" in the bowl than the other. As Paul states, the 7 gram max weight limit does not guarantee working floats when below. I have contacted Lockwood aviation and will let you know how the exchange to new floats under warranty goes.

    Thanks Paul for raising the issue.
  • Ivo Smyly
    by Ivo Smyly 5 months ago
    New SI
    Introduction of new floats (pair) for ROTAX® Engine Type 912 and 914 (Series)
    In the course of continuous development and standardization, new floats (pair) ROTAX® part number 861188 have been introduced. These new floats (pair) are manufactured with a higher compaction rate and contain a recessed brass guide.
    https://legacy.rotaxowner.com/si_tb_info/serviceinfo/si-912-029.pdf
  • Paul Hamilton
    by Paul Hamilton 5 months ago
    Yes Ivo and all I was waiting for this. Hopefully this will fix the chronic float problem on the FOURTH QC try.
  • Thomas Nielsen
    by Thomas Nielsen 4 months ago
    UPDATE: Received "new" floats from Lockwood under warranty. They weighted in at a perfect 2.8 grams each. Now installed, and two flights later, I still have fuel dripping from carb vent line, but it is a little less. Lockwood says that it cannot be the new floats since they were in spec and if bad would take much longer time to arbsorb fuel and become "heavy". They think my carbs are out of sync or my prop pitch not set within 2/10th of a degree which would easily cause the float valves to leak. The Engine was a new install on a new trike and with a new prop, currently with 23 hours.
  • Paul Hamilton
    by Paul Hamilton 4 months ago
    Tom,
    Call me and I may be able to solve this problem. 775 772 8232
  • Paul Hamilton
    by Paul Hamilton 1 month ago
    The new latest and greatest floats are into the Rotax retail distributers for purchase, being shipped and they are pricey. Hope they fixed this :-/
  • joey martin
    by joey martin 1 month ago
    My buddy has had the fuel dripping out the vent lines for many many years on his 912 after i told him about the float problem i seen in this thread he started investigating his floats was not saturated his problem ended up being to much fuel pressure. he put a gauge on his trike and discovered that it had 6 to 8 pounds of fuel fuel pressure it would fluctuate during flight and it had the original fuel pump on it that is to much pressure for the floats so he put a inline regulator on it knocked it down to 4 pounds and it runs clean and no more dribbles. that is something else to check if anyone's problem persist.
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