Matronics Email Lists :: View topic - Rough starting 912uls

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Rough starting 912uls

Matronics Email Lists Forum Index -> RotaxEngines-List

View previous topic :: View next topic

Author Message

rickwehrmann

Joined: 27 Oct 2008
Posts: 2

Posted: Mon Oct 27, 2008 11:54 am Post subject: Rough starting 912uls

Hello, 

I recently purchased an Interplane Skyboy with a 912ULS. The engine often, not always, exhibits an extreme high frequency vibration on start-up. I cannot get the revs up much above 2000 during one of these attacks, and the best technique I have discovered to smooth out the engine is to get the revs up as high as possible (again, about 2000), and then chop the throttle, and quickly open just a crack. If the engine catches, it is smooth as glass. If not, I repeat until it does smooth out. 

I have had my mechanic do the pneumatic carb sync, and generally go through the motor. All cylinders are 78 pounds, plugs look good, etc.

It feels almost like a 2-stroke engine that is '4-stroking'. All four cylinders seem to be firing during one of these episodes, as all the exhaust pipes are hot. I have had this happen on a dead cold start, and a restart after only sitting for 10 minutes.

Does this sound familiar to anyone?

Thanks in advance,

Rick

peteohms

Joined: 31 Oct 2007
Posts: 224
Location: Leander, TX

Posted: Mon Oct 27, 2008 1:22 pm Post subject: Rough starting 912uls

My 912 does the same thing but I smooth it out with choke.  About a minute 

it will hold an idle.



Pete

Kitfox III



Hell Paso, TX



---

_________________
Pete
Leander, TX
Kitfox III, 912ul, Grove

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

Posted: Mon Oct 27, 2008 1:23 pm Post subject: Rough starting 912uls

Hi! Rick

It sounds to me to be the slipper clutch that needs adjustment. Unless

you can say you don't have one I'd have a check done on it!

Sounds balmy but I believe it is quite likely>

Regards

Bob Harrison G-PTAG Rotax 914.



--

Goodone

Joined: 13 Sep 2008
Posts: 49

Posted: Tue Oct 28, 2008 12:30 pm Post subject: Re: Rough starting 912uls

I have an 912 UL without a slipper clutch and my engine sometimes does this when cold. Mine will often stop running during this chatter. I have no choke but was told just recently by a friend (with the same engine as mine) that his does the same thing every time. He said that he now starts the engine with the primer out and gives it a shot of gas when the engine starts into this mode. I intend to try it the next time to see if it works.

rickwehrmann

Joined: 27 Oct 2008
Posts: 2

Posted: Tue Oct 28, 2008 4:10 pm Post subject: Re: Rough starting 912uls

Thank you all for the responses, I will check those out. The clutch might be the trouble.

Does anyone know of information on-line about adding a primer, as my plane does not have one.

Thanks again,

Rick

rampil

Joined: 04 May 2007
Posts: 870

Posted: Wed Oct 29, 2008 10:38 am Post subject: Re: Rough starting 912uls

Rotax 9 series engines are designed to work with their intrinsic

mechanical fuel pump and an electric boost pump. The factory does not

provide guidance on priming pumps.



That generally means they are unnecessary or not condoned.

_________________
Ira N224XS

daveaustin2(at)primus.ca
Guest

Posted: Wed Oct 29, 2008 11:25 am Post subject: Rough starting 912uls

I'm puzzled..

Why would you need a primer when you have a choke?

Mine will start rough if the throttle is open at all, which negates the 

choke action.  Make sure the throttle butterfly is fully to the idle 

position (against the idle adjustment screws).  Or is the idle too high?



Dave Austin  601HDS - 912

peteohms

Joined: 31 Oct 2007
Posts: 224
Location: Leander, TX

Posted: Wed Oct 29, 2008 11:43 am Post subject: Rough starting 912uls

I have both and I use both.  Works fine for me.



Pete

Kitfox III

Hell Paso, TX



---

_________________
Pete
Leander, TX
Kitfox III, 912ul, Grove

rparigor(at)suffolk.lib.n
Guest

Posted: Wed Oct 29, 2008 12:07 pm Post subject: Rough starting 912uls

Just a note on Bing type 64 constant depression carb it uses a enriching

circuit. It needs to be at or close to idle to function. On my 1988 BMW

R100GS that uses that carb the first thing to clog is the enriching

circuit. If can't get it started when cold out and don't feel like taking

apart the carbs, can blow into the overflow line and essentially shoot raw

fuel into the venturi. Works great. Vent location on a 912 or 912S is

critical that it is near ambient pressure. on a 914 it must be plumbed

without leaks to the enriching solenoid output.



Also too there is a mod to make enriching circuit more rich for cold

weather operations.



All that said, you could fashion a blow into carb float bowl to shoot raw

fuel into venturi.



Have fire extinguisher at hand!



Ron P.

jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Thu Oct 30, 2008 2:30 pm Post subject: Re: Rough starting 912uls

It can be the (optional) slipper clutch too loose or more likely the "dog" preload of the torsional dampening device needs checking. There is a procedure for testing this with weighing scales on the prop and locking the crankshaft with a test plug. Friend's 912 wouldn't start until the dogs were replaced.

Ralph

_________________
Ralph - CH701 / 2200a

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Thu Nov 13, 2008 4:52 am Post subject: Re: Rough starting 912uls

Rough starting is usually started by too high idle setting or having the throttle open a little like on a Contilyco.

  if engine has suffered for sometime the dog and spring tension must be check ed along with the slipper clutch torque. 

If no slipper clutch is fitted remove the prop shaft and check the splines for where. The play by having worn splines makes the prop "bounce " of the power then compression strokes. 

  If engine starts like this accelerate through it quickly , or if not possible stop engine and retry with the throttles fully closed.

 On the 912s best to have the idle set at 1650 rpm hot and use the choke just to get it to catch then open up and off with the choke.

  

 Happy landings

Kev

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

Roger Lee

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

Posted: Thu Nov 13, 2008 6:41 am Post subject: Re: Rough starting 912uls

Hi Rick,



Several of the people here have good advice. There are a few more things to think about after you have tried and made sure your choke and throttle combination is correct on start up. This could be a carb issue and could be caused by 3-4 different items with the carbs or a gearbox issue. 

How many hours on the carbs since new or when were they rebuilt? The carbs can be synced even if you have problems and still run like garbage when under higher throttle settings or at start up. Carb fuel and air leaks can cause some of these issues. Do you happen to know how old the engine is?

What are the plugs gapped at? Not a big issue, but a contributing one and should be checked just so it doesn't add to your headache.

Another big one that some of the guys have talked about is getting your gearbox inspected. How many hours are on the engine?



Please let us know when you get it nailed down so we all can learn.



Good Luck

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

Display posts from previous:

	Matronics Email Lists Forum Index -> RotaxEngines-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum