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503 Problem

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rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Wed Nov 18, 2009 4:17 pm Post subject: 503 Problem

Hello,



I could use some help. I am running out of idea's. I have a 503 with dual Bing 54 carb's. The engine starts and runs well up to about 2000 RPM. After this RPM it has nothing left it just bogs. I have gone through both carbs so many times I could do it in my sleep. I don't think it is  fuel pump problem because I have rebuilt it and I have used the primer bulb to try to compensate for a potentially bad pump but this has no effect. The other day I ran it up to a point just before it bogged and put three fingers in front of the inlet of the right carb and got it to bog. I put three fingers in front of the inlet on the left carb and got a 1000 RPM rise. The carb on the left is an older type so I bought a brand new carb. Would you believe it? Same exact reaction. I went through the timing but I will probably go through it again to double check. Any body got any idea's? I have done so much that I can't even remember it all. 



Ray W.

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Wed Nov 18, 2009 4:49 pm Post subject: 503 Problem

If choking off one carb causes an rpm increase it may be that you have an air leak somewhere... crankshaft seals perhaps, or a case seal?  Have you done a pressure test on the engine?



 The previous owner of my plane (Cuyuna, not Rotax, but they're similar) went crazy trying to get the   engine to run right until he discovered the center crankshaft seal was bad (or more accurately, a good seal installed incorrectly).



 -Dana



 At 07:17 PM 11/18/2009, rayw wrote:



 [quote]I could use some help. I am running out of idea's. I have a 503 with dual Bing 54 carb's. The engine starts and runs well up to about 2000 RPM. After this RPM it has nothing left it just bogs. I have gone through both carbs so many times I could do it in my sleep. I don't think it is  fuel pump problem because I have rebuilt it and I have used the primer bulb to try to compensate for a potentially bad pump but this has no effect. The other day I ran it up to a point just before it bogged and put three fingers in front of the inlet of the right carb and got it to bog. I put three fingers in front of the inlet on the left carb and got a 1000 RPM rise. The carb on the left is an older type so I bought a brand new carb. Would you believe it? Same exact reaction. I went through the timing but I will probably go through it again to double check. Any body got any idea's? I have done so much that I can't even remember it all. 



 Ray W.



 



 

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George Myers

Joined: 10 Jan 2006
Posts: 76
Location: San Marcos, Texas

Posted: Wed Nov 18, 2009 4:54 pm Post subject: 503 Problem

Points or ducati ignition? 

Check that there are no restrictions in your muffler. Had something similar

happen to me once & it was a big mud dobber nest in the muffler.

 



--

Richard Pike

Joined: 09 Jan 2006
Posts: 1670
Location: Blountville, Tennessee

Posted: Wed Nov 18, 2009 6:13 pm Post subject: Re: 503 Problem

Take some pitch out of the prop and see what happens.



Richard Pike

MKIII N420P (420ldPoops)

rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Sat Nov 21, 2009 10:46 am Post subject: Re: 503 Problem

First of all I want to thank those that replied. Every idea I received gave me something to consider. Here is where it's at today:



After running up to 1500 RPM. I used a can of starting fluid and sprayed every nook and cranny. Pretty much every where except in the carb inlets (ok just a little to see what would happen)(It bogged). I heard no change at all other than that. When I wasn't spraying I was watching CHT's and EGT's. CHT's could not get warm enough to even get into the green. EGT's could barely get in the green if I ran up to 2000 RPM and let it go for awhile. Sounds like a very rich condition yes???



Now for a little back ground: I bought this airplane from a couple of good ol' boys in St. Joe, MO. (That is a story in itself). Now mind you I have nothing against good ol' boys from St. Joe......... When I got it home and got down to details. I found a lot of things not acceptable to me.  I have never heard it run or saw it fly. Normally a red flag but I got it so cheap I couldn't pass it up. My wife would argue but I still think it was worth it. Any way enough rambling. 



Both carbs have main jets = 158, Idler jet = 45, Needle jet = 2.7, Jet needle = 11K2. The top ring of the needle has the O-ring and the clip right under it on the second ring. The air screw is at .5. The floats arms are level when the carbs are upside down. I believe I have the recommended 1/2 inch of space between the top of the float bowl and the gas level in the bowl. 



Altitude at Stevens Point, WI (5 miles away) is 1050 ASL. The three finger test mentioned in my last post still has me scratching my head. It tells me that the carbs are still different in some way. Is a K&N air filter considered a "silencer"?



Thanks every one,



Ray W.

rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Sat Nov 21, 2009 7:13 pm Post subject: Re: 503 Problem

Hello,



I cannot seem to find a Rotax 503 repair manual for purchase. Does any one know of a source. It would be nice to know things like bolt torque specs and pattern, plug gap, acceptable cylinder compression etc.



I did a compression check and got 115 front and back. The plug gap should be ok because the plugs are brand new. The prop is bolted on and is providing a suitable load. All fuel lines are brand new including the impulse line for the fuel pump. The impulse line is 6 inches long and was ordered from LEAF specifically for this purpose. The entire fuel system is brand new. This airplane did not even have a fuel tank when I bought it. 

It is an older engine with points ignition. I was told the engine has 160 hours. Both slides are reacting the same when responding to the throttle.



Dana, You mentioned a pressure test and I did not. Please elaborate.



Thanks every one!!



Ray

lcottrell

Joined: 29 May 2006
Posts: 1494
Location: Jordan Valley, Or

Posted: Sat Nov 21, 2009 8:06 pm Post subject: 503 Problem

I suppose that you have checked to make sure that the  nylon cup and the needle jet is installed correctly? 

 Larry C

 [quote]   ---

_________________
do not archive

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Sat Nov 21, 2009 8:47 pm Post subject: Re: 503 Problem

 	  rayw wrote: 	
		  Hello,



I cannot seem to find a Rotax 503 repair manual for purchase. Does any one know of a source. It would be nice to know things like bolt torque specs and pattern, plug gap, acceptable cylinder compression etc.



I did a compression check and got 115 front and back. The plug gap should be ok because the plugs are brand new. The prop is bolted on and is providing a suitable load. All fuel lines are brand new including the impulse line for the fuel pump. The impulse line is 6 inches long and was ordered from LEAF specifically for this purpose. The entire fuel system is brand new. This airplane did not even have a fuel tank when I bought it. 

It is an older engine with points ignition. I was told the engine has 160 hours. Both slides are reacting the same when responding to the throttle.



Dana, You mentioned a pressure test and I did not. Please elaborate.



Thanks every one!!



Ray 	




Ray,

Sorry to hear you're having engine troubles.  Recently I had some and got lots of good advice on things to check.  Read through this thread for additional ideas:

http://forums.matronics.com/viewtopic.php?t=62699&highlight=



I believe you have to take the 2-stroke Rotax class to get the repair manual.  All the other manuals (installation, operators, maintenance) can be downloaded from http://www.rotax-owner.com/ under "support>engine manuals".

_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

planecrazzzy
Guest

Posted: Sun Nov 22, 2009 6:49 am Post subject: Re: 503 Problem

Since your already "in" the Carb...



Be sure to check the the "Main" Jets are tight...



 I had them come loose once...

.

.

        Gotta Fly...

Mike & "Jaz" in MN

.

.

.

PS  That reminded me of this place.... You all probably know

about it...

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

.

.

.

HPIM1170.JPG

Description:

Brake set-up on my Wittman "Buttercup"

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110.76 KB

Viewed:

17806 Time(s)

Dana

Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA

Posted: Sun Nov 22, 2009 7:09 am Post subject: 503 Problem

rayw wrote:



  	  Quote: 	
		  > Dana, You mentioned a pressure test and I did not. Please elaborate. 	


 A pressure test checks the crankcase and shaft seals.  You remove the intake manifold and exhaust, put a 1/8" rubber sheet seal over the openings, then reinstall the exhaust and intake manifold.  You attach a fitting with a valve and pressure gauge to the pulse fitting and apply pressure with a hand pump, close the valve, and verify that the pressure holds for a certain period of time.



 You do this for both sides of the engine... I don't know about the 503, but the Cuyuna has a pulse fitting on both cylinders (one is normally plugged)... to run the test on the plugged side you remove the plug and put the fitting in the other side temporarily).  For the Cuyuna the test is 3psi for 3 minutes and if that holds, then 10psi for 3 minutes... with a caution not to exceed 12psi or you damage the engine.



 I can attach the page from the Cuyuna manual that describes the test and how to make the tester if you'd like.  Usually a leak causes a lean condition, not rich, and spraying the starting fluid on the seals will indicate it as well... but I'm not clear on what symptoms are when the center seal (between the two cylinders) is bad.  I do know that the center seal on my engine was bad and gave the previous owner fits until a snowmobile shop discovered the problem (the Cuyuna is basically a snowmobile engine)... all I recall him saying was that "it didn't run right".



 -Dana

 --

  But if we LEGALIZE it, we can't take your HOUSE!    [quote][b]

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Sun Nov 22, 2009 11:10 am Post subject: Re: 503 Problem

 	  rayw wrote: 	
		  

After running up to 1500 RPM....

EGT's could barely get in the green if I ran up to 2000 RPM...

The plug gap should be ok because the plugs are brand new. 



Ray 	




Ray,



The recommended gap on the spark plugs is .015 to .019  of an inch.  When I buy the NGK BR8ES I always have to adjust the gap because the gap is too big when it's new out of the box.



I set my idle screw so I don't idle any lower than 2000rpm.  Anything lower causes vibration that could cause damage to the gearbox or motor.  If you've been running it around 1500rpm and had lots of vibration something could have worked loose as Mike suggested.



Also you won't see your EGT and CHT rise very much, if at all when you are just idling the engine around 2000rpm.



You might want to check that both carbs have the new style retaining cup, o-ring and clip as described here:

http://www.ultralightnews.ca/bing/needleclipupdate.htm



Check your choke seal.  If your engine was like mine, sitting up with ethanol gas before I bought it, the seal could have deteriorated.



Lots of things to check.  May you have good luck.

_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

Richard Pike

Joined: 09 Jan 2006
Posts: 1670
Location: Blountville, Tennessee

Posted: Sun Nov 22, 2009 12:13 pm Post subject: Re: 503 Problem

If you have an Ivo, take a little pitch out of the prop and see if it revs up. If it does, then check the points and timing. If the points are worn, or the timing is retarded, the engine will not rev up under normal load, but will rev up under a lesser load. I would say just check the points and timing first, but on a Kolb, they are hard to get to.

 

On the other hand, if you don't have an Ivo, adjusting the prop is not a 2 minute operation, so maybe you ought to just go ahead and check the points & timing anyway...



Something that is counter intuitive is that if you have a single carb 503 and the prop is pitched correctly, and then you go to the dual carb setup, you may have to take some pitch out of the prop, because sometimes the engine will just moan and blow fuel air mixture out the carbs when you try and rev it up. When I had a 503 with a 66" two bladed Warp, that was my experience.



Richard Pike

MKIII N420P (420ldPoops)

rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Sun Nov 22, 2009 3:55 pm Post subject: Re: 503 Problem

Hello,



As soon as I wrote that the plugs were new and should be ok I knew I was gonna' catch it. Rightly so.........My High school shop teacher would have smacked me for that comment. 



I just went out and checked them. They are far in excess of .015/.019. I did not close them up yet or run the engine but I am going to feel super silly if this is the trouble.  Oh yeah.....With the plugs out I did another compression test. I got 112 in back and 120 in front. Seems low..Is it?

rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Sun Nov 22, 2009 5:59 pm Post subject: Re: 503 Problem

Is there any one on the list from UK, Ireland or Iceland?

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Sun Nov 22, 2009 6:48 pm Post subject: Re: 503 Problem

 	  rayw wrote: 	
		  Hello,



As soon as I wrote that the plugs were new and should be ok I knew I was gonna' catch it. Rightly so.........My High school shop teacher would have smacked me for that comment. 



I just went out and checked them. They are far in excess of .015/.019. I did not close them up yet or run the engine but I am going to feel super silly if this is the trouble.  Oh yeah.....With the plugs out I did another compression test. I got 112 in back and 120 in front. Seems low..Is it? 	




Ray,

Hope the spark plug gap is the solution.  I copied those values from another website but the Maintenance Manual for the 503 states .016-.020.  I set mine at .018 and it runs good at that.

_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

R. Hankins

Joined: 18 Jan 2006
Posts: 185
Location: Grants Pass, Oregon

Posted: Sun Nov 22, 2009 11:21 pm Post subject: Re: 503 Problem

" I got 112 in back and 120 in front. Seems low..Is it?"



Neither number is cause for concern, but I have never seen that much difference between the two cylinders on my engine.

_________________
Roger in Oregon
1992 KXP 503 - N1782C

rayw

Joined: 18 Jul 2009
Posts: 25
Location: Wisconsin, Central

Posted: Sun Nov 29, 2009 1:36 pm Post subject: Re: 503 Problem

Just wanted to update on the problem. I finally had a chance to run it yesterday after gapping the plugs to 0.018". It seemed to run a tad smother but did not help it gain any RPM. Last night I decided to swap carbs from left to right and try the "three finger test" again. While I had the carbs off I decided to pull all the jets and again verify the sizes. The sizes were all proper. I used a magnifying glass to look carefully at each one. I could see light through each jet when I held it up. before reassembling the carbs I took the main jet and needle jet and gently inserted the needles into each jet just to see how far they would go up the taper of the needle. One of the Main jets did not go as far as the other. I gently twisted and heard (more like felt) a subtle snap. The jet then slid up the needle as far as the other main jet would go. The best way to describe it is there was a crust build up in side the jet. Prior to this I did spray the jets out with carb cleaner but now I know that was not enough. Took it out today and tied it down and got it to run up to 6200 RPM.

Thank you again for all the helpful suggestions.



Ray W.

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Sun Nov 29, 2009 5:55 pm Post subject: Re: 503 Problem

 	  rayw wrote: 	
		  Just wanted to update on the problem. I finally had a chance to run it yesterday after gapping the plugs to 0.018". It seemed to run a tad smother but did not help it gain any RPM. Last night I decided to swap carbs from left to right and try the "three finger test" again. While I had the carbs off I decided to pull all the jets and again verify the sizes. The sizes were all proper. I used a magnifying glass to look carefully at each one. I could see light through each jet when I held it up. before reassembling the carbs I took the main jet and needle jet and gently inserted the needles into each jet just to see how far they would go up the taper of the needle. One of the Main jets did not go as far as the other. I gently twisted and heard (more like felt) a subtle snap. The jet then slid up the needle as far as the other main jet would go. The best way to describe it is there was a crust build up in side the jet. Prior to this I did spray the jets out with carb cleaner but now I know that was not enough. Took it out today and tied it down and got it to run up to 6200 RPM.

Thank you again for all the helpful suggestions.



Ray W. 	




Yeah!  Good for you!  Congratulations on finding the problem.

_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

cristalclear13

Joined: 19 Sep 2007
Posts: 363
Location: Southeast Georgia

Posted: Sat Dec 05, 2009 4:44 am Post subject: Re: 503 Problem

 	  rayw wrote: 	
		  Hello,



I cannot seem to find a Rotax 503 repair manual for purchase. Does any one know of a source. It would be nice to know things like bolt torque specs and pattern, plug gap, acceptable cylinder compression etc.

Ray 	




Ray, I know you found the answer to your engine problem.  I don't know if you got the answer to your above question.  It looks like CPS sells the repair manual you were looking for.



http://www.rotaxparts.net/scripts/prodView.asp?idproduct=1213



This is the one I got when I took the 2-stroke class

#1247 Rotax 532-582-618 Repair Book ($29.95)

even though it doesn't exactly cover the 503, most of the information in the manual applies to the 503 as well.

_________________
Cristal Waters
Kolb Mark II Twinstar Rotax 503 DCSI Sept 2007 - sold Sept 2012
Private Pilot Aug 2008
ELSA Repairman for N193Y April 2008
Rotax 2 stroke maintenance April 2009

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