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Trouble cold starting a 912

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wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Wed Feb 01, 2006 6:10 am Post subject: Trouble cold starting a 912

I'm a new owner of a 912UL powered Mod IV. I'm having trouble starting this thing when temperatures approach freezing. I drained my battery this morning and I didn't get a single pop out of the thing. Being new with this type, I'm wondering if there's something I'm missing because even at 60F I still find that this thing requires a lot of cranking to start. 



I'm getting a lot of conflicting instruction from various sources. Some sources say that I'm supposed to pump the throttle to prime, others don't mention it. From my experience, pumping the throttle doesn't seem to have any effect. Another area of confusion is the throttle setting for starting. Some suggest setting the throttle at idle and others say pull all the way back and then feed it in as the engine fires. 



One thing I suspect is the battery. It's currently fitted with a standard motorcycle battery and I wonder if it has the power. During this morning's failed attempt, the digital tach (which seems to be very accurate) was reading between 150 and 200 rpm. Is that fast enough? 



I've also read something about a new high torque starter for the 912 series. Was this upgrade an answer to cold starting problems? 



Any other suggestions would be greatly appreciated.



Luis Rodriguez

N824KF

cliffh(at)outdrs.net
Guest

Posted: Wed Feb 01, 2006 6:43 am Post subject: Trouble cold starting a 912

You will get much easier starts and much smoother starts if you will preheat 

the engine.

Any time the OAT get much below 40 degrees I put a hair dryer under the cowl 

and throw a blanket over the cowl. I let it run about 30 minutes, just to 

warm the carbs. Make a much smoother start.

Floran H.

---

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Wed Feb 01, 2006 7:40 am Post subject: Re: Trouble cold starting a 912

Sounds like something to try. Unfortunately, the airplane is currently tied down at the local airport (no hangar space available). I'd run an extension cord but the FBO doesn't open till 9am. Things are warming up by then so it's not as big an issue. 



Looking through the rotax operators manual again, I found a note in the trouble shooting section indicating that you need a minimum of 250 rpm at start to get any spark. I don't think I was making 250 this morning. I had a feeling about that a cheep motorcycle battery. Any suggestions for a proper battery.



Searching the internet, I found a note from some other forum regarding the gap on the spark plugs. I'd like to check that but I can't find anything in the operators manual about it. What is the suggested spark gap?



Any thoughts on the proper starting procedure? Does pumping the throttle really do anything? What are other 912 owners out there doing?

kerrjohna(at)comcast.net
Guest

Posted: Wed Feb 01, 2006 7:43 am Post subject: Trouble cold starting a 912

The recommended starting procedure includes full out throttle and full fuel enrichener (choke).  I have found this to be very effective even to temperatures below freezing.



John Kerr



-------------- Original message -------------- 

From: "Floran Higgins" <cliffh(at)outdrs.net> 



[quote] 

 

 You will get much easier starts and much smoother starts if you will preheat 

 the engine. 

 Any time the OAT get much below 40 degrees I put a hair dryer under the cowl 

 and throw a blanket over the cowl. I let it run about 30 minutes, just to 

 warm the carbs. Make a much smoother start. 

 Floran H. 

 ---

taildragon(at)msn.com
Guest

Posted: Wed Feb 01, 2006 8:51 am Post subject: Trouble cold starting a 912

The Bing constant depression carburetors incorporate the use of a choke that require the throttle to be "closed" to work. That is, if the throttle is not set at CLOSED, the choke will not create enough vacuum to work. No primer is necessary with this setup.



[quote] ---

rjdaugh(at)rapidnet.com
Guest

Posted: Wed Feb 01, 2006 9:55 am Post subject: Trouble cold starting a 912

Luis,

If you have the idle set too fast, you can't shut of the main throttle as

required.  See Roger's comment and John's below.  You do need the main

throttle path shut down to make the "choke" work.  The Choke is a separate

carburetor that puts a rich mixture into the intake manifold.  Idle should

be set no higher than 1800 rpm according to Phil Lockwood.



I have no trouble starting my 912S at temperatures in the teens F following

Clint Bazzil's procedure.  It just pops right off immediately.  



Randy



.           

--

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Wed Feb 01, 2006 11:35 am Post subject: Re: Trouble cold starting a 912

Is that 1800 RPM with a cold engine or warm? I know I can get it that low when it's cold but the minimum idle climbs as the engine warms up. Is there anything on the ouside of the carb that I can see to be sure that the throttle is fully closed?



I gather that no one is concerned with the 200RPM starter speed?



edit: 

Sorry, who is Clint Bazzil? I don't see that name in any of the posts above. Is the procedure in question one of the ones posted here?

rjdaugh(at)rapidnet.com
Guest

Posted: Wed Feb 01, 2006 12:13 pm Post subject: Trouble cold starting a 912

Luis,

I am pretty sure that is with the engine warm.  I can't get my engine to

idle that low when it is cold.  I keep the choke circuit open for about a

minute while the engine warms up at about 2500 - 2800 rpm.



Randy



.           

--

lcfitt(at)sbcglobal.net
Guest

Posted: Wed Feb 01, 2006 4:25 pm Post subject: Trouble cold starting a 912

Luis,



I think you are well on your way to understanding and loving your R-912.



The minimum recommended idle speed is 2100-2200 rpm.  This is to protect the 

dog gears in the reduction drive from excessive wear due to the pulses the 

engine makes on each power stroke vs the propeller that is turning at a 

constant Speed.  The absolute minimum idle speed as set by the set screw 

should be below that, and that is the 1800 figure you mentioned.  The 

minimum idle speed is set with a screw that is below the throttle arm on the 

carburetor.    I have a friend that can close his throttle to stop and he 

will consistently land shorter than I will because there is more drag on his 

prop than mine.  I don't like the idea of inadvertantly stopping the engine 

in the patttern and  having to do a restart then.  The recommended 1800 rpm 

will keep it moving, but will allow for some drag on final. By turning the 

set screw ccwise you until it is no longer hitting the tab, you can have the 

butterfly valve fully closed.  If you want to do this, I would recommend 

counting the turns on the screws so you can get them both back to the 

original position.  Carburetor balance is very important at lower RPMs for 

smooth running.  There are methods for blancing described in the Rotax 

Maintainance Manual.



As I recall, the engine needs something like 600 RPM from the starter - 

others with better info, please chime in here - for the ignition system to 

produce a spark.  If the battery is weak, you can crank all day and nothing 

will happen if the cranking speed is insufficient to produce a spark.



Hope this helps a bit.



Lowell

---

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Feb 02, 2006 1:17 pm Post subject: Re: Trouble cold starting a 912

Started fine this morning at 55F OAT. She was turning over much faster at 350RPM. For now, I'm going to assume for now that the current battery just isn't up to the task on cold days. Thanks for all the help.

gofalke(at)sbcglobal.net
Guest

Posted: Thu Feb 02, 2006 4:31 pm Post subject: Trouble cold starting a 912

According to Lockwood, the cranking speed for the 912 must be 300 RPM or above in order to create a reliable spark for the engine to start.

   

  Herb Gottelt M4-912UL

  Mt. Prospect, IL



wingnut <wingnut(at)spamarrest.com> wrote:

  



Started fine this morning at 55F OAT. She was turning over much faster at 350RPM. For now, I'm going to assume for now that the current battery just isn't up to the task on cold days. Thanks for all the help.





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