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Stratus problems

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btucke73(at)yahoo.com
Guest

Posted: Mon Feb 19, 2007 8:59 am Post subject: Stratus problems

Gents,



     I got a call from an HDS builder not too far from

me who is having problems with his Stratus.  I fly

with a Corvair, so I am not much help.  His engine

runs great on climb out, but when he throttles back on

downwind, it runs very poorly.  I have a hunch that is

is a sync problem between his dual bing carbs, but I

am not a Subaru guy...  I will relay any

troubleshooting tips any of you may have.



VR/



Brandon Tucker

601 HDS / TD / Corvair

70 hours



 

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larry(at)macsmachine.com
Guest

Posted: Mon Feb 19, 2007 10:41 am Post subject: Stratus problems

Brandon,

I called Tim this morning and discussed his problem at length.  He 

needed the Bing

Carburetor manual and jetting information. I provided Matronics and Bing 

links, plus files

to help him safely disassemble the carburetors and made him aware of 

other issues, valve guide

info, ignition modules (TP45 NAPA), and also dual ignition drawings, etc. 



It seems his first item of concern was main jet and mid jet sizes and 

the fact

that he needed to temporarily reinstall the foam filters to get a richer 

mixture to correct excess

airflow until he can digest the Bing carb jetting info and sent 

historical data to make adjustments.



He has a very expensive vernier dual throttle cable that he can set up 

for purely push pull operation,

so I doubt his throttle plates are out of sync.



Larry McFarland - 601HDS at www.macsmachine.com

do not archive



Brandon Tucker wrote:

 	  Quote: 	
		   



 Gents,



      I got a call from an HDS builder not too far from

 me who is having problems with his Stratus.  I fly

 with a Corvair, so I am not much help.  His engine

 runs great on climb out, but when he throttles back on

 downwind, it runs very poorly.  I have a hunch that is

 is a sync problem between his dual bing carbs, but I

 am not a Subaru guy...  I will relay any

 troubleshooting tips any of you may have.



 VR/



 Brandon Tucker

 601 HDS / TD / Corvair

 70 hours

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btucke73(at)yahoo.com
Guest

Posted: Mon Feb 19, 2007 11:33 am Post subject: Stratus problems

Larry,



     Your post is the exact reason why I sent him in

your direction first.  You are and asset to this

forum.



VR/



Brandon Tucker

601 HDS / TD / Corvair

70 hours

 

Want to start your own business?

http://smallbusiness.yahoo.com/r-index

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Crvsecretary(at)aol.com
Guest

Posted: Mon Feb 19, 2007 11:37 am Post subject: Stratus problems

Hi Brandon:

  

 Maybe not a synch problem, but a mixture problem......

  

 Between 3/4 throttle and WOT, the slides on the Bings are all the way  up, pulling the needles (virtually) completely out of the main jets.   Engine runs well.  BUT, turning downwind the throttle closes and the  needles drop into the main jets and now the mixture is controlled by the  taper of the needle.  There are many different needles available with  different tapers, but let's assume the needle is correct.  The needle is  held in place by a clip installed in the slide, and there are usually three or  four different grooves machined into the needle.  Installing the  needle on the groove nearest the END of the needle puts the needle further INTO  the main jet for a given position of the slide, so the mixture is  lean.  The groove furthest AWAY from the end of the needle pulls the needle  OUT of the main jet for a given position of the slide, so the mixture is  rich.

  

 I'd look at this first.  It's easy to check, just handle the  diaphragms VERY carefully while pulling the top of the carb  off.  He'll have to resynch anyway if the throttle adjustments are  tampered with as the top comes off.....

  

 Good luck.

  

 Tracy Smith

 Do Not Archive

  

  

 In a message dated 2/19/2007 12:06:38 PM Eastern Standard Time,  btucke73(at)yahoo.com writes:

  	  Quote: 	
		  -->    Zenith-List message posted by: Brandon Tucker    <btucke73(at)yahoo.com>



Gents,



     I got a    call from an HDS builder not too far from

me who is having problems with    his Stratus.  I fly

with a Corvair, so I am not much help.  His    engine

runs great on climb out, but when he throttles back on

downwind,    it runs very poorly.  I have a hunch that is

is a sync problem between    his dual bing carbs, but I

am not a Subaru guy...  I will relay    any

troubleshooting tips any of you may have.



VR/



Brandon    Tucker

601 HDS / TD / Corvair

70  hours

	


 

  

  [quote][b]

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tshank(at)core.com
Guest

Posted: Mon Feb 19, 2007 5:46 pm Post subject: Stratus problems

There are some other factors that might be at work. I am about thirty hours into the test program for my 601HD with a Stratus Suburu. Carb synch is very important and can be hard to do. I originally synched mine on the ground with a motorcycle flow gage. The problem was since I didn't want to stand next to the engine with the prop on I could only do this at idle. I also checked it during the flight test for start of movement. What can be a complicating factor is the motor mounts. I made a change in my thrust angle and found that my engine did not as smoothly at midrange. I checked the plugs for similar burn and checked the needles. I finally realized that the spacer I put behind my upper left motor mount caused that carb to be a little ahead of the right carb. Readjusting the cable restored the performance. As the original post notes full power is fine because both carbs are at their stops midrange depends on the cables. I am thinking of making a velocity sensor that could be mounted on the carbs so they could to check under load with the mounds deformed , but that is still a thought in progress. The root problem seem to be the throttle design for the dual carbs, if there is plenty of slack in the cables engine movement won't be a factor,  but I know on mine it is. 

 

 Tim Shankland

 

 Crvsecretary(at)aol.com (Crvsecretary(at)aol.com) wrote: [quote]               Hi Brandon:

    

   Maybe not a synch problem, but a mixture problem......

    

   Between 3/4 throttle and WOT, the slides on the Bings are all the way up, pulling the needles (virtually) completely out of the main jets.  Engine runs well.  BUT, turning downwind the throttle closes and the needles drop into the main jets and now the mixture is controlled by the taper of the needle.  There are many different needles available with different tapers, but let's assume the needle is correct.  The needle is held in place by a clip installed in the slide, and there are usually three or four different grooves machined into the needle.  Installing the needle on the groove nearest the END of the needle puts the needle further INTO the main jet for a given position of the slide, so the mixture is lean.  The groove furthest AWAY from the end of the needle pulls the needle OUT of the main jet for a given position of the slide, so the mixture is rich.

    

   I'd look at this first.  It's easy to check, just handle the diaphragms VERY carefully while pulling the top of the carb off.  He'll have to resynch anyway if the throttle adjustments are tampered with as the top comes off.....

    

   Good luck.

    

   Tracy Smith

   Do Not Archive

    

    

   In a message dated 2/19/2007 12:06:38 PM Eastern Standard Time, btucke73(at)yahoo.com (btucke73(at)yahoo.com) writes:

    	  Quote: 	
		  --> Zenith-List message posted by: Brandon Tucker <btucke73(at)yahoo.com> (btucke73(at)yahoo.com)

     

 Gents,

     

      I got a call from an HDS builder not too far from

 me who is having problems with his Stratus.  I fly

 with a Corvair, so I am not much help.  His engine

 runs great on climb out, but when he throttles back on

 downwind, it runs very poorly.  I have a hunch that is

 is a sync problem between his dual bing carbs, but I

 am not a Subaru guy...  I will relay any

 troubleshooting tips any of you may have.

     

 VR/

     

 Brandon Tucker

 601 HDS / TD / Corvair

 70 hours

     

     

     	
   

    

       	  Quote: 	
		  

	
 [b]

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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