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mismatched egt's

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carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Sat Jun 20, 2009 2:28 pm Post subject: mismatched egt's

Hi folks...I've been lurking for some time and finally need to chime in with a question.



My Model II Kitfox is almost 20 years old now and I've only put 150 hours on it.  I let it sit idle for 4 years without running the 582 Rotax and decided to resurrect it this summer.  Did a top overhaul and inspected the crank (didn't split the case), buttoned it up with new gaskets after decarbonizing everything and it runs fine.  When I had the cylinders off, everything looked spotless.  Good needle bearings on the con rods, etc.  Cylinders don't even look broken in with new looking crosshatching on the walls.



Problem is this.  Carbs won't match no matter what I do.  Front cylinder runs hotter all the time.  I've adjusted the jet needle, put in larger main jet (.175), matched the slides, etc and the fron always runs 100 to 150 deg hotter.  Plugs show it too.  The front ones are obviously leaner with only slight browning of the insulator.



So the question is, if my crank seals are failing, wouldn't that lean BOTH the carbs out or are these symptoms something else?

Tom Jones

Joined: 12 Mar 2006
Posts: 752
Location: Ellensburg, WA

Posted: Sat Jun 20, 2009 5:47 pm Post subject: Re: mismatched egt's

 	  Quote: 	
		  So the question is, if my crank seals are failing, wouldn't that lean BOTH the carbs out or are these symptoms something else? 	




No, the crankcase is sealed between the cylinders.  A leak can affect just one cylinder.



Here's a link to the CPS Rotax maintenance articles.  Scroll down to number 59, "Leak testing".

http://www.800-airwolf.com/articles.htm



For what its worth, gage errors can cause the temps to read different.  Although 100 to 150 degrees is quite a bit.

_________________
Tom Jones
Classic IV
503 Rotax, 72 inch Two blade Warp
Ellensburg, WA

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Sat Jun 20, 2009 6:46 pm Post subject: Re: mismatched egt's

Sounds like you need crank seals. 



Contact  toll free 866-418-4164  - can ship out seals overnight to you or we can re seal it for you 

Dave

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WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sun Jun 21, 2009 6:27 pm Post subject: Re: mismatched egt's

I doubt this is the case since you say your plugs are also indicating the difference, but it could be exasperating the situation.  My EGT display went bad and started indicating 75+ degrees difference.  The first test I did was swap wires from the front and rear exhaust ports.  Left needle was higher then the right before and after the swap so I knew it was the instrument which prevented me from digging into the carbs (that day at least).  Good luck with it.



James

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Tue Jun 23, 2009 8:31 am Post subject: Re: mismatched egt's

why go straight for crank seals?  First thing to do is what Whurly said.  Swap EGT senders and see if the high reading follows a sender or the display.   Akflyerbobs did the same thing and it was the display not the seals.  Another thing to check is for any corrosion or loose connections where the senders plug into the display.  Any added resistance in a connection will cause a huge error in the reading.  Start the checks at the most obvious (and cheapest and easiest to fix) then move on to bigger and more expensive / time consuming repairs.

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Thu Jun 25, 2009 7:14 am Post subject: Re: mismatched egt's

 	  akflyer wrote: 	
		  why go straight for crank seals?  First thing to do is what Whurly said.  Swap EGT senders and see if the high reading follows a sender or the display.   Akflyerbobs did the same thing and it was the display not the seals.  Another thing to check is for any corrosion or loose connections where the senders plug into the display.  Any added resistance in a connection will cause a huge error in the reading.  Start the checks at the most obvious (and cheapest and easiest to fix) then move on to bigger and more expensive / time consuming repairs. 	


Here is what he said  >>   The plugs indicated a difference in temps >>   so why would changing  leads change ?  I assuming he is showing a leaner reading on both plugs and EGT reading .



Dave

 	  Quote: 	
		  

Problem is this. Carbs won't match no matter what I do. Front cylinder runs hotter all the time. I've adjusted the jet needle, put in larger main jet (.175), matched the slides, etc and the fron always runs 100 to 150 deg hotter. Plugs show it too. The front ones are obviously leaner with only slight browning of the insulator.



So the question is, if my crank seals are failing, wouldn't that lean BOTH the carbs out or are these symptoms something else?

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Thu Jun 25, 2009 8:48 am Post subject: Re: mismatched egt's

yep, had my head square in my a$$ on that one.. I thought I read it all but guess I didn't.  I was thinking of an issue akflyerbob had that was very similar, we changed seals and it did not do anything to the high reading.  ended up being the EGT indicator not the leads.

patreilly43(at)hotmail.co
Guest

Posted: Thu Jun 25, 2009 3:13 pm Post subject: mismatched egt's

 The front cylinder usually runs cooler than rear due to cold air entering cowling and hitting front cyl first on air cooled. I had a 30 horse C fan cooled C Kohler engine on an ultralite C no cowling C but it had cooling baffels on the engine. I ran a colder plug on the rear cylinder. It gave a more uniform burn color on the front and rear plugs. It was a pusher set up rather than a tractor. Has anybody tried different heat range plugs between front and rear cylinders? Seems like water cooled wouldn't have the greater temp differencial as an air cooled.

  

 Pat Reilly

 Mod 3 582 Rebuild

 Rockford C IL

 

 	  Quote: 	
		   Subject: Re: mismatched egt's

 From: dave(at)cfisher.com

 Date: Thu C 25 Jun 2009 08:14:35 -0700

 To: kitfox-list(at)matronics.com

 

 --> Kitfox-List message posted by: "dave" <dave(at)cfisher.com>

 

 

 akflyer wrote:

 > why go straight for crank seals? First thing to do is what Whurly said. Swap EGT senders and see if the high reading follows a sender or the display. Akflyerbobs did the same thing and it was the display not the seals. Another thing to check is for any corrosion or loose connections where the senders plug into the display. Any added resistance in a connection will cause a huge error in the reading. Start the checks at the most obvious (and cheapest and easiest to fix) then move on to bigger and more expensive / time consuming repairs.

 

 

 

 Here is what he said >> The plugs indicated a difference in temps >> so why would changing leads change ? I assuming he is showing a leaner reading on both plugs and EGT reading .

 

 Dave

 

 > 

 > Problem is this. Carbs won't match no matter what I do. Front cylinder runs hotter all the time. I've adjusted the jet needle C put in larger main jet (.175) C matched the slides C etc and the fron always runs 100 to 150 deg hotter. Plugs show it too. The front ones are obviously leaner with only slight browning of the insulator.

 > 

 > So the question is C if my crank seals are failing C wouldn't that lean BOTH the carbs out or are these symptoms something else?

 

 

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carlisle

Joined: 20 Jun 2009
Posts: 72
Location: Sioux Falls, SD

Posted: Thu Jun 25, 2009 5:02 pm Post subject: Re: mismatched egt's

Have switched probes and even replaced them without much difference.



BUT...When I switched to the next-up main jet size in both carbs (.165mm up to .175mm) and moved the jet needle one notch richer, the problem was fixed.  Now EGT's are within 25 to 50 deg of each other and plugs have nice brown tint to the insulator and look the same.



Boy I love these 2-stroke engines.  They kind of force you to go the extra mile and understand their workings more than most 'start and go' engines.  Knowledge is power!



Here's another theory.  I have individual air filters on each carb instead of the single oval filter who's lumen is common to both carbs.  I wonder if the one up front experiences a little different 'ram air' pressure as a result and might cause the front to run leaner.

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Fri Jun 26, 2009 10:56 am Post subject: Re: mismatched egt's

dont know if you have read the articles by Mike Stratman about the proper care and feeding of your 2 stroke, but it does make you understand the different circuits on the carbs and how to properly tune them instead off guessing at what you need to do.



I am right at sea level so I have 2 jets.  170s in winter 165s in summer.

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