Rotax Starting Woes

[PaulN]

Hi all,

 

My CT2K with Rotax 912s is refusing to start ... aaaagghhh!!

 

I'm in a cold climate and the CT is parked in an open shed out of immediate weather but still subject to frost and wind. Winter starting has always been difficult but this winter more so. Even jumping from the car battery won't get a result. W/out the jump leads from the car my 8 amphour cold battery voltmeter reads 11.5v, with the car it reads 12.5v to 13.0v.

 

Have tried the Soft Start Module from Conair in UK with no apparent change.

 

What is happening? With the above 13.0v supply, full choke, fully closed throttle I hit the start and the Rotax grinds over momentarily, attempts to fire then kicks back violently disengaging the starter. This happens over and over to the point that I have to stop in fear of the engine lurching from its mounts (slight exageration, but only slight). It appears that the engine just will not wind over fast enough to overcome the ignition.

 

I've also tried rewiring the start switch and incorporating a push start button to allow winding over the Rotax before switching on the ignition. Still kicks back violently as soon as the ign is engaged.

 

Any ideas out there? What do you recommend for a battery if I were to replace the one I have? Any help please.

 

I'm just about to the point of removing the engine to check out the sprag clutch condition .

 

Paul

 

 

[storchy neil]

paul does it wind over with no choke sounds like get a guts full of fuel do you turn off fuel when you park it

 

 

[Yenn]

I am not a Rotax driver but from the symptoms it sounds as if the ignition is too far advanced. For it to kick back it seems to be firing so the fuel is getting in and the compression is OK. I am not aware of how a 912 is timed but one of the experts in this forum may be able to advise you.

 

 

[jetboy]

Paul I dont own one but have worked with a few that have had the same problems. There are a number of rotax SBs on the subject esp. the 912S.

 

The most recent case was a 912 that would crank and sputter but not pick up from rough idle. A Phone call across the ditch to your good agents sorted this (after 2-3 days stuffing about locally). The procedure was to lock the throttle to idle, remove the prop and start up. It ran like a kitten. That means the gearbox dog clutch preload was too low, requiring O/H of the box and a new 30 deg. dog if I understand correctly. This was carried out and fixed the problem for a few hrs, until the starter occasionally would throw out. We measured the cranking current per the details in the SB for the 912S and it read 69 amps so it was off with the starter clutch and now thats fixed its back to normal running. TTIS around 180 hrs.

 

Ralph

 

 

[wanabigaplane]

The tendency to fire, then lurch and not make it to the next firing position is interesting, and it is with this characteristic in mind that I make the following suggestions. However, now that you have a consistent symptom to describe, the first thing to do is ring Bert Flood. I have found them to be very helpful - they may know straight off what it is.

 

In reading your post I get the impression this problem started one morning when you tried to start the engine, versus a problem that just got worse over time. When my engine is very cold, or has a low battery, it eventually fails to wind over. It has never thrown a tantrum as you describe. Also, the symptom is consistent, and now occurs every time. I am also assuming you have not just modified, or changed something between when it was working, and now when it is not.

 

If this is so, I would be looking for something that is actually broken, failed, or disconnected, rather than something that is loose, or out of adjustment, or marginal in its operation. In this case continuing to try to start it, or getting a bigger battery is not the answer: you might be doing damage.

 

Since it is firing, I would rule out fuel, choke, coil, spark plugs, carburetor, etc for the moment. No doubt you would have turned it over all compressions by hand (with the ignition off) in your pre-flight to see that there is nothing obviously untoward.

 

I can think of two reasons the motor could be failing to turn over after firing - the ignition system is firing at full advance, or there is a failure of the clutch to impart enough torque to the propeller for the propeller to carry the engine through to the next firing.

 

The Rotax engine has a dual ignition system, and I think the modules incorporate the automatic advance. There do not seem to be any parts in common between the two systems, although I don’t know how or where the trigger sensors are mounted. (if this mounting has become loose and moved, you would have had an exciting last flight). It is unlikely both modules would have failed in the same way at the same time. To confirm that he failure to start is not caused by one of the ignition modules firing at full advance, try them one at a time. If you have a select key and a start button, this is easy. On my engine, this is not the case. Both modules are supplied with 12 volts by their own red supply wire right at the module, and it is easy to unplug these one at a time there.

 

In the Rotax Line Maintenance manual (which I downloaded from Rotax site on the internet) there is a procedure for checking the setting of the overload clutch, that does not involve disassembly of the gearbox. It does, however, require some work, so get your overalls on.

 

If that fails, rip some more pages out of ERSA, and call Adrian.

 

Jack. :):)

 

 

[Admin]

Paul

 

Could be that the spark plug gaps are a little big for cold starts - just a thought!

 

 

[Guest pelorus32]

Hi Paul,

 

There has been a previous thread about starting the 912s engines. I think it revolved around installing an upgraded starter motor and also that failure to do that would result in damage to various engine components.

 

I will try and search that thread out - I think that it's in the Tecnam area.

 

Regards

 

Mike

 

 

[Guest pelorus32]

Paul,

 

this is one link. I think there is also an earlier one:

 

http://www.recreationalflying.com/forum/showthread.php?t=1672

 

Regards

 

Mike

 

 

[PaulN]

Don't you love this forum ... everyone is so helpful, thanks fellas ;).

 

Hello New Zealand - Ralph. Actually you're closer than you might think, I have an Airmaster prop hanging off the Rotax .... Ahhh, maybe that's the problem . Ralph, how would a faulty slipper clutch affect the starting?

 

Have tried variations on plug gaps ... not the issue.

 

Have tried variations of choke and throttle settings ... not the issue.

 

Not something that has just happened out of the blue but rather grown from an irritation to a "flying nowhere today" problem over these colder months.

 

Thankfully, no "exciting" flights lately but read on re ignition timing (trigger coils).

 

Have spoken with Wal at Bert Flood's and given various probable causes and "remove the engine, send it to us and we'll fix it". Read on for ways that we are addressing some of his suggestions ... before writing big cheques.

 

Compression is good on all 4.

 

The ERSA is now pageless so have recruited Adrian's help and donned the overalls.

 

Mike, I'll take some time tomorrow scanning through the Tecnam thread, thanks.

 

Here's my progress to date.

 

Slipped (also an exaggeration) the Rotax out this afternoon and checked out a few things.

 

1. The starter certainly is a tiny unit. The recommendation to upsize to the more powerful unit is now on the agenda.

 

2. Carried out a load test on the sprag clutch (with the aid of my ever helpful L2 Adrian) and determined that it shows no sign of wear, that is, grips under load as it should with no sign of slipping or releasing.

 

3. Discovered the trigger coil clearances are out of whack.

 

4. The water/oil cooler front mounting brackets broken from severe shaking, and ....

 

5. The engine mount frame is ever so slightly bent and twisted (a bit like it's owner).

 

What next? Acquire a higher cranking power battery of say 12 amphours (any suggestions?), fit heavier power leads to the starter (may not be necessary but takes the std CT light weight leads out of the equation), adjust the trigger coil gaps as per the Rotax manual, fit a new high torque starter motor, and fit a Soft Start Module (from Conair in the UK) just for the peace of mind. And of course repair the broken brackets and bent frame. Then the joys of putting it all together again to test with fingers crossed .

 

I'll let you know how things work out.

 

Thanks again,

 

Paul

 

 

[jetboy]

Paul,

 

The dog clutch ( not the slipper clutch) if it has become worn will directly affect starting because when the torque reversals occur at startup they are not absorbed by the 15 deg or 30 deg slippage normally afforded in the gearbox and the prop is able to kick back the to the crank. This shakes the engine so much that either one of the carbs falls off (not kidding) or the fuel is disprupted in the floats preventing a proper start. It was Bert Floods who told us to take the prop off to check for this, and they were right on the money there.

 

Secondly, if your worried about the starter do the bulletin

 

SB 912 042

 

You need a DC clamp meter that will read up to 200 amps if you cant find someone with one its a good excuse to go to jaycar or DSE and get one they are handy to have anyway. One thing we noticed the SB says to start the engine but you cant get a reading that quick so we assumed they really men to crank the engine with ign. off to get the reading

 

good luck

 

Ralph

 

 

[eastmeg2]

If your aircraft battery is only 8 Ah that definitely sounds too small, great weight saver though I'm sure.

 

The 582 trike I used to fly had a 12 Ah as fitted new in the factory and always has trouble starting the 582 if it had not been flown earlier the same day though was sometimes ok the next morning in warmer climates.

 

My newer 912 trike has a 17Ah battery which certainly does better, and it better as the 912 lacks the lawnmower starter rope the 582 had.

 

Cheers,

 

Glen

 

 

[eastmeg2]

Also, simply connecting jumper leads to this small battery probably would not be adequate to get your cranking amps up to what's required (You will get some voltage drop accross the leads regardless of any claims made about them). You ought to try directly connecting a larger/newer battery directly into your aircraft.

 

 

[Guest Andys@coffs]

...The 582 trike I used to fly had a 12 Ah as fitted new in the factory and always has trouble starting the 582 if it had not been flown earlier the same day though was sometimes ok the next morning in warmer climates.

Glen

 

All my 582 starting woes went away as soon as I worked out the best thing to do is drop each carbi bowl, empty on the gnd, and fill with fresh fuel from the low point drain. In this way the starter is trying to start the motor with the motor able to immediately start. Without it, the first 20-30secs are spent driving the fuel pump to fill the bowls. By then the battery has given its best. Doing it my way, choke on. sees a start almost immediately winter or summer.

 

I also find that Next day or days after flying the bowls usually are left with an oily residual after the quality fuel has evaporated away, so even when the fuel pump has refilled the resultant mix is never optimal.

 

regards

 

Andy

 

 

[PaulN]

An update guys.

 

Wouldn't you know it . Found out today from the Bert Floods that the newer more powerful starter motor is larger than the original and it just won't fit into the CT2K .

 

Have adjusted the trigger coil gaps to .013" all round.

 

Now looking at setting up a test bench for the engine to facilitate torque testing the slipper clutch before reinstalling. Wal reckons that the 912s does not have a dog clutch :confused:.

 

Glen ... I'm persuing a new larger battery. Wal at Bert Flood suggests a 22 amphour as minimum. Wow, I'd need a bigger engine bay or install it in the baggage area if I go that big. Think I'll settle for something like 12 amphour.

 

More to follow, to be sure.

 

Paul

 

 

[Matt]

G'day Paul, had similar issues with a 12 amp-hour battery in the Sportstar in the very cold months up here - nothing quite as bad as you've reported, just couldn't get the thing to start. Replaced it with a 16 amp-hour unit and had no issues after that. Also found that pre-heating the engine worked...usually involved taking the engine cover off and letting it sit in the sun for about half hour...I'm sure there's more effective engine warmers out there.

 

Also thought it a bit ironic that an engine built in Europe with their winters had issues starting in the cold weather!

 

Cheers,

 

Matt.

 

 

[Knighty]

Hi Paul

 

Something very similar continued to happen with an A/C here in Orange (similar weather conditions of COLD!!!). I know you have already mentioned this however the power leads from the battery to the starter maybe just way too light. Simple test is to try and start the plane and immediately place your hand on the BOTH leads, if they are warm then the full juice from the battery is being lost. You can try to temporarily place a second set of jumper leads that will effectively double your cable capacity from point A to point B to see if this makes a difference. Dont forget if you replace the active cable from the battery to the starter with a heavier type then make sure you replace the -VE as it is under exactly the same amount of pressure (amp drain). Remember: a chain is only as strong as its weakest link!

 

I hope you get it all sorted out.

 

Knighty

 

 

[Deskpilot]

Hi Paul, do the right thing, chuck that engine away and throw in a Jabiru 2.2:laugh:

 

Good luck, Doug

 

 

[wanabigaplane]

Hi Paul,

 

I would be surprised if your battery was only 8 amp hour! That's ridiculously small for this application. If the battery is too small, or the leads are too thin, the engine should find it hard to crank over. But it would be unlikely to cause it to kick back violently as you are suggesting as a result.

 

If something is faulty in your present setup, and you overcome it by adding a bigger battery or bigger starter, the original fault will still exist and rear its ugly head again as it gets worse. I suggest you leave changing the system till after the fault is found.

 

(unless the battery really is only 8 amp hours)

 

Jack.

 

 

[PaulN]

Jack,

 

It really is only 8 amphours, as are all CTs . I'm off to Fyshwick today for a new better battery. I guess I'll then need to make up a custom cradle for it as no doubt it will be larger and heavier. Yep, upgrading the leads as well. Adrian's on the case so am confident all will work out in the end.

 

Cheers,

 

Paul

 

 

[Guest Juliette Lima]

Hi paul,

 

Aircraft Spruce (and others) sell a REIFF engine pre-heater for Rotax 912/914 for around $US 215.00....looks like the unit would have to be transformerd from 240V

 

This could be the go for exceptionally cold climates and difficult to start Rotax 912/914 engines.

 

I'm getting one for those odd frosty mornings....don't like seeing the engine vibrating, even if it is only for a short period.

 

Cheers

 

JL

 

 

[Guest Juliette Lima]

Hi Paul and all in colder environments,

 

Have been checking out the Reiff preheater systems site and reading... 'why should you preheat your engine?'

 

There is also an ARTICLES link and some of it makes for very logical reading.

 

Hope this helps...

 

JL

 

 

[slartibartfast]

They do look the bee's knees JL, and some very interesting reading, but did you see the small print? "These prices are for 120v systems. For 220v, add 25%".

 

 

[PaulN]

Thanks for the tip JL. This had already crossed my mind (that's a very short trip) but alas my hangar (shed) has no power available.

 

Went to Fyshwick Battery Factory today and now have a Deka ETX15 (14 Ah @ 10hr rate, 190 CCA, 4.3kg). At $180 I reckon this is pricey. After buying I checked around on the net and can buy in US for AUS$75. Even if freight was $50, importing your own would have to be cheaper, but a bit of a worry if you have problems with it.

 

I'll let you know how this goes, but will be a couple of weeks before ready to test.

 

Paul

 

 

[Guest Juliette Lima]

Hi Slartibartfast,

 

Thanks for the extra info...preheating engines is certianly an issue in the US judging by the extensive number of articles on the Reiff site....on a lighter note, I read a post re.a cheap preheater.....Thick doona over the motor with a hairdryer setup under the engine!!!!

 

Cheers

 

JL

 

 

[slartibartfast]

The Adrian that Paul is talking about warms his Jabiru with a paint stripper gun on cold mornings. When I applied the gun to take his Jab to Camden Haven (it was -7C outside), the gun moved when I wasn't watching and heated the cowl to the point of bubbling it.

 

I nearly gave up and stayed home (glad I didn't).

 

There has to be a safer way.

 

I was going to rely on an extra battery to help turn mine over, but your link to the warmer site made me realize that there's more to it than crank power. The oil is too thick to lubricate at first. And there's the different expansion rates of the various metals. I will have to seriously consider one of those warming solutions.

 

I need one that can be turned on remotely, because they take hours to warm the engine.

 

Thanks again JL.

 

Ross