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Rotax 912 ULS kicking back! Newbie needs a hand ..

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cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Sun Oct 11, 2009 3:03 pm Post subject: Rotax 912 ULS kicking back! Newbie needs a hand ..

Hey everyone,



I'm a freshly minted pilot who just bought a Kitfox V with a 912 ULS.  It got down to 11F the night before I decided to take it for a spin with a more experienced Kitfox pilot.



I hopped in the plane, turned off the mags and hit the starter to limber up the engine.  Let it crank for about 4 or 5 seconds, then turned on the mags and cranked again.  The engine would turn over but wouldn't catch.  I probably tried to start it a total of 10 times or so (full choke) before giving up.  I walked it into a friend's hangar and let it warm up a bit.  Tried to start it again with very different results - now the engine was kicking back!  Carefully tried a few more times and decided to check the engine.  I removed the carb bowls to check for good flow.  One was hardly flowing at all so I pulled out the float needle, blew air/cleaner in there and checked again.  It flowed nicely, so I put everything back.  Still kicked back.  Tried hooking the battery up to a charger, still kicked back.  All 8 plugs sparked fine.  Pulled the plugs and torched them a bit thinking they might be fuel fouled.  Still no go.  Sumped the tanks - no visible water.  When starting on only one mag, the startup is much much smoother but doesn't have quite enough to start by itself.



I'm all out of ideas ..



I'm going to buy a new Odyssey 680 battery, get new plugs, and install the soft start module .. might build a little space heater with dryer ducting to heat the cowling, too.  Any other ideas?? Thanks!!



Carl

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sun Oct 11, 2009 3:17 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Hi Carl,



Your OAT's are too cold. The engine needs 225rpm to start and with an engine that cold it might not happen. You may hear the engine crank, but it will never reach the required rpm to start. The spark is too weak at low rpms.

First re-gap the plugs to .022. make sure that battery is at full charge and is not old and can't produce the power you need. Next the engine must be preheated. Look at this post and video from Rotax and it will tell you everything you want to know about the colder starting. You must live in a pretty cold climate if it is already 11F. You definitely need a pre-heater for your engine in some way shape or form. It is not good for the engine to try and start at these really cold temps without being warmed up.

The preheating system Rotax recommends is called Tanis. There are other ways to preheat, but this Tanis system seems the way to go. Watch the video and you'll see why.



http://www.rotax-owner.com/reviews/reviews.htm

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Sun Oct 11, 2009 3:51 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Roger,



Thanks for the advice.  Hopefully I didn't damage the engine with the numerous cold start attempts ...?



Carl

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sun Oct 11, 2009 8:05 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Watch the video from Rotax in my post and tell me what you think.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Mon Oct 12, 2009 6:22 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Excellent video - every aircraft owner should watch that .. a THREEFOLD increase in required starting torque simply due to cold weather!!  That heater is pretty dang expensive for what it is, I just ended up attaching dryer duct to a 1500W space heater.  Hopefully that will do the trick with a couple of fiberglass batts draped over the cowling.



How durable are these Rotax engines?  Can they take 20 or 30 kickbacks without incurring damage?  I'm concerned that my Sprag clutch might be damaged after all this abuse .. going to re-try later this week once my new plugs, battery, ssm, etc get here.



Carl

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Oct 12, 2009 9:13 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Hi Carl,



Your engine should be ok, but don't continue with any more of the kick backs.

The space heater should work and put it on a timer so it has a chance to preheat for 3-4 hours before you show up at the airport.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Tue Oct 13, 2009 12:13 am Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Check you have the throttles FULLY closed and full choke too.

 Soon as the throttle is opened the enrichment circuit does not work well enough. Warm the engine up on the choke until it will take throttle opening.



If you have many hours on the engine it may be worth getting the backlash checked as when is too low the engine will kick back alot more.



There is now a different flywheel with a softer ignition start setting, also now there is a soft start kit  but this comes without the flywheel.



Or move south

Kevin

_________________
Back home .................

ptag.dev(at)tiscali.co.uk
Guest

Posted: Tue Oct 13, 2009 2:46 am Post subject: Rotax 912 ULS kicking back! Newbie needs a hand ..

If your engine is fitted with a sprag clutch it may well need torque

adjustment. Kick backs are a sure sign of this.

Regards

Bob Harrison Europe G-PTAG



--

m.tucciarone(at)hotmail.c
Guest

Posted: Tue Oct 13, 2009 3:05 am Post subject: Rotax 912 ULS kicking back! Newbie needs a hand ..

Reiff has a preheater for Rotax also and is much less money.

http://www.reiffpreheat.com/Rotax912.htm



Also I had the same problem with my 912s when it had about 300 hours. It

turned out to be the sprag clutch. I brought the engine to Lockwood. Ended

costing me a grand by the time I was done.



Those kick backs are bad for the carb sockets, the gear box and the wires

that come out of the ignition modules. Some of my wires broke so I had to

have that repaired also. 



--

deltadart48

Joined: 23 Aug 2009
Posts: 2
Location: Vashon Island, WA

Posted: Tue Oct 13, 2009 10:29 am Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Cold temperature starts notwithstanding, one of  the best things you can do for your 912 series is to install the soft start module made by Bullyhawk. Check out the video review on the ROAN website. When the engine is hot it can kick pretty hard on start and the module really tames that down. I installed them on my Aircam and really noticed the difference.



Ed Pierson

dashwood

Joined: 24 Jan 2009
Posts: 73
Location: sw ontario canada

Posted: Tue Oct 13, 2009 7:14 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

i find my rotax will kick back if it is shut down too hot and running on low octane mogas. not ever when runniing on premium fuel. 

i also use a simple heater i assembled myself. easy to use and carry on plane if i must. one bottle will run for hours but i only need to heat for about 30min preflight. . i also have a car battery wrap that is wrapped around oil res. all winter. usually plugged in for the same 30  min or overnight if i know i have an early flight with -01deg C.

just a small camp heater LPG/ propane, a 6"duct pipe for floor register , reducer and a 4" elbow.  i fit the heater inside the pipe and prop into position. cool air mixes with heated air as it rises up the pipe. a blanket (skin)over the cowl and leave the cowl vents open to allow air to escape out by the gearbox. you can feel this air and determine when engine is toasted enough. I also have a very large sheepskin at the hanger.  I clean the windscreen after every flight. and put it fuzzy side down on the screen to keep road dust off in summer , my hanger backs onto a main gravel road. i use it over the cowl as a insulating blanket in the winter and wrap the legs around prop to keep snow out in the winter, open front hanger. makes a great ground sheet to Neal on to work on the plane. as of yet i have no cabin heat so take the skin with me sometimes to insulate whatever.. also helps as an engine wrap when parked on a cold windy apron while attending early morning winter flyin breakfasts

edit ..... sorry files where too big .... try these

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Last edited by dashwood on Wed Oct 14, 2009 7:55 pm; edited 4 times in total

pchristensen10(at)austin.
Guest

Posted: Wed Oct 14, 2009 7:46 am Post subject: Rotax 912 ULS kicking back! Newbie needs a hand ..

Is it just me?  I couldn't access the photos.



Pete



---

craig(at)craigandjean.com
Guest

Posted: Wed Oct 14, 2009 8:43 am Post subject: Rotax 912 ULS kicking back! Newbie needs a hand ..

Same here. They also don't work if you go to the web-based forum.



-- Craig



--

Goodone

Joined: 13 Sep 2008
Posts: 49

Posted: Wed Oct 14, 2009 11:43 am Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

What is in the bottle? Sure would like to be able to see the pictures. Please try again.

cschmokel

Joined: 04 Aug 2009
Posts: 23
Location: Pullman, WA

Posted: Thu Oct 15, 2009 9:28 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Well, I'm embarrassed to say that it just took cranking on mag B until it finally caught.  Not used to these high compression engines!!  Starts up pretty easily now, but I'm still replacing the battery and getting the SSM.  Thanks for all your help guys!



Carl

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sun Oct 18, 2009 5:55 pm Post subject: Re: Rotax 912 ULS kicking back! Newbie needs a hand ..

Hi Dashwood,



This is a bad idea.

Probably not a good idea to use a propane type heater around fuel. If you have any vapors under a cowl then you may get a surprise, not to mention Rotax carbs at times leak from the floats not shutting off the fuel completely.



(30 year retired firefighter)

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

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