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447 mid-range rough running

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undoctor

Joined: 21 Oct 2008
Posts: 212
Location: Bethelhem, PA

Posted: Wed May 13, 2009 2:49 pm Post subject: 447 mid-range rough running

Folks,



I have a question for any two cycle experts who'd like to help a 

frustrated FireFly owner.



My FireFly has a 447 Rotax, and last week after I taxied about 100 yards 

at about 3500 rpms, I gave it full throttle to take off, and the engine 

lost power and wouldn't rev up.  It felt like it was loading up.



I removed the jets and cleaned everything up, cleaned the K&N air 

cleaner and tried it again today.  Same drill when giving it full 

throttle from lower rpms, so I moved the needle one notch leaner to the 

second notch from the top and tried it again.  Now it'll run up to the 

recommended 6200 rpms static, but what I believe was the original 

problem still seems to be there.



It seems to idle OK, and WOT is strong, but mid-throttle is rough and 

unpredictable.  When I try to get it to 48 - 5200 rpms, where most 

curising will be done, it seems to run rough and it's difficult or 

impossible to get it to lock on 4800 rpms.  Problem is, when it's 

struggling to hold about 4300 rpms and you open the throttle just a 

smidgen, it suddenly runs up to about 5600 rpms, running smooth and 

strong. 



If anyone can give me an idea where to start looking for the problem, 

I'd sure appreciate it.



Thanks,



Dave Kulp

Bethlehem, PA

K Dilks

Joined: 22 Sep 2008
Posts: 108
Location: UK

Posted: Wed May 13, 2009 9:21 pm Post subject: Re: 447 mid-range rough running

Run the engine at the "rough rpm for a couple of minutes , then cut the engine, dont run at at for long before cut and check the plugs. Sounds like its mixture but which way.....

  Check fuel level in the carb bowl .Disassemble the main jet and the needle jet and clean, this along with the needle position controls the mid range mixture. Put the needle back to the normal position , dont run lean!



 Check the idle jet is clear as this effects the mid range too .

 Do the mixture check first.

Hope this helps

Kev



 Also check the carb mounting rubber socket does not have a split.!

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

conrad

Joined: 07 Feb 2007
Posts: 16
Location: Banbury. UK

Posted: Wed May 13, 2009 11:18 pm Post subject: Re: 447 mid-range rough running

Check the needle clip is under the white plastic cup.

Check out the IPC available from www.rotax-aircraft-engines.com to see the correct assembly order.



Conrad

www.conairsports.co.uk

williamtsullivan(at)att.n
Guest

Posted: Thu May 14, 2009 4:23 am Post subject: 447 mid-range rough running

I just went through the Bing on my 447 for about the same reasons.  I had rough running at an idle- shaking.  When the throttle was advanced, the engine would either hesitate or lose rpm's.  Seemed to run good at full throttle.  Air screw adjustments didn't do any good.  I cleaned it out and put a kit in it.  The choke plunger was missing the seal, goo all over the inside, and the needle clip was above the plastic cup instead of under it.  The "O" ring on top of the needle was missing.  Runs a lot better now.  I used Scott Olendorf's trick on both the main spring and choke spring, and it was very easy to re-assemble.  I still have a little skip, or shudder, that may be a plug wire.  If you need Scott's web adress, I can supply.

  

                                                 Bill Sullivan

                                                 Windsor Locks, Ct.

                                                 Kolb Firestar 447

 [quote][b]

undoctor

Joined: 21 Oct 2008
Posts: 212
Location: Bethelhem, PA

Posted: Thu May 14, 2009 6:53 am Post subject: 447 mid-range rough running

[quote][b]Thanks for the tips, Kev.  I'll give it a shot and see if it helps.  The plane's been sitting a 

lot for the last year, so if I still have a problem, the carb comes off and goes to a two-cycle

pro who will overhaul if for me.



Thanks, one more time.  Wanna get flying!!!



Dave Kulp

Bethlehem, PA



FireFly 11DMK



 

      Run the engine at the "rough rpm for a couple of minutes , then cut the engine,

      dont run at at for long before cut and check the plugs. Sounds like its mixture

      but which way.....

        Check fuel level in the carb bowl .Disassemble the main jet and the needle jet

      and clean, this along with the needle position controls the mid range mixture.

      Put the needle back to the normal position , dont run lean!

      

       Check the idle jet is clear as this effects the mid range too .

       Do the mixture check first.

      Hope this helps

      Kev

      

      --------

      Austria .............

      

[/b][b]

williamtsullivan(at)att.n
Guest

Posted: Thu May 14, 2009 8:12 am Post subject: 447 mid-range rough running

Dave- If it's been sitting for a year, the carb has goo in it.  I would bet on it.  Look at the Rotax manual.  The carb is very easy to clean out, but you do need some small metric tools, two cans of spray carb cleaner, and Q-tips.  I think Roger Lee said he'd do it for $50 plus parts and freight.  Parts for a re-build probably are another $50.

  

                                         Bill Sullivan

                                         Windsor Locks, Ct.

                                         Kolb Firestar 447

 [quote][b]

rparigor(at)suffolk.lib.n
Guest

Posted: Thu May 14, 2009 1:58 pm Post subject: 447 mid-range rough running

Hi BillWhat is:"Scott Olendorf's trick"?Thx.Ron Parigoris [quote][b]

williamtsullivan(at)att.n
Guest

Posted: Thu May 14, 2009 2:13 pm Post subject: 447 mid-range rough running

Ron- Scott's trick is on how to get the springs in and out of the carb without a special tool, and it's probably easier and faster.  His website address is:

       http://kolbfirestar.googlepages.com/home

 Go to Bing 54 tricks.  Enjoy.  Cleaning and reassembly was not very difficult for me, but the book didn't match what I found in my carb- mine was assembled incorrectly, worn, and missing an "o" ring.  It ran anyway, not well, but ran.

  

                                               Bill Sullivan

                                               Windsor Locks, Ct.

                                               Kolb Firestar 447

 [quote][b]

undoctor

Joined: 21 Oct 2008
Posts: 212
Location: Bethelhem, PA

Posted: Sun May 17, 2009 9:55 am Post subject: 447 mid-range rough running

Folks,



Thanks lots for the info about the mid-range roughness.  I now have some 

experience to go on whereas before I had about zero.  Next week I'll go 

over it with the recs I've gotten from you and if it still doesn't run 

well the carb comes off for overhaul.



Also, the method of installing the spring is great.  That's one of those 

"why didn't I think of that" deals.  Thanks so much!



Best,

Dave Kulp

ralston

Joined: 14 Jun 2009
Posts: 2

Posted: Sun Jun 14, 2009 5:25 pm Post subject: Re: 447 mid-range rough running

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