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503 Teardown Report

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R. Hankins

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

Posted: Wed Apr 16, 2008 9:51 am Post subject: 503 Teardown Report

I have seen a few questions about the 503 on the list lately.  I just finished tearing down my 503 after 452.0 hrs of trouble-free service, so I thought I would pass along my data.  



Pistons:

The pistons were inside the wear limits for diameter, out-of-round, and taper.  The only visible wear was on the intake side of the piston where it slides by the intake port.  In this area some of the textured finish had been worn shiny.  Both pistons showed similar wear.  Both wrist pins were slightly discolored. One of them had a slight wear mark where the hardened washer sits on it.  Carbon on the piston tops was approx .015 thick on the rear piston and 0.010 thick on the front piston.  The spark plugs for the front cylinder also showed less carbon.  This was traced to a slight leak in the front crank seal that was leaning the mixture to the front cylinder slightly.  The resulting difference in EGT's had grown slowly to 100 deg over the last 20 hrs of operation and was the main reason for the full tear down.  There was also a slight weep of oil under the front of the engine. The ring end gap was within wear limits and all rings moved easily in their slots and feel "springy".  Ring groove wear was still within limits.



Cylinders:

The cylinders both measured the same.  All areas were within wear limits except for a narrow band of wear just above the exhaust port.  This area stayed inside maximum diameter, but was worn to the 0.002 out of round limit.  They are currently being bored 1st over.



Heads:

The heads are shiny on the underside except for two thumbnail size dots of carbon discoloration across from and on opposite sides of the spark plug hole.



Crank:  

The crank was near the maximum run out spec of 0.003 on the fan end.  I suspect this may have led to the demise of the crank seal on that end.  The only visible wear was inside the piston end of the connecting rods where the cageless needle bearings run.  The honing crosshatch was worn smooth in a small area area about 40deg down from the vertical on one side of the con rod bore.  There was some visible corrosion stains on the counter balances, but nothing that looked fresh or would leave a streak on a white rag.



All in all, I believe the engine could have gone another 100 or so hours if the front crank seal had not begun to leak.  It gave me ample warning signs of brewing problems, while continuing to run like a swiss watch.  The EGT discrepancy between cylinders was (verified by switching probes) and the oil seep were clear signals.   I am replacing every moving part of this engine: crank, pistons, wrist pins and bearings, fan bearings, fan belt etc.  Total cost for parts and machining comes to $1780.76 plus return shipping on the crank core.  This gives a rebuild cost of just under $3/hr.



I used the AV-1 oil From CPS for the first 119.6hrs.  I did a decarbon at this point and replaced the wrist pin bearings.  The carbon from the AV-1 was hard as a rock and took many hours of scrubbing to remove.  I used Penzoil Marine premium synthetic blend from wally world with two oz of Marvel mystery oil per six gallons for the next 325.4 hrs.  The last 7 hrs I switched to Penzoil air cooled with Marvel.  I have performed annual carbon inspections and have not needed to decarbon again.



Sorry for the long post.  I hope this info is helpful to someone.

_________________
Roger in Oregon
1992 KXP 503 - N1782C

jim

Joined: 03 Nov 2006
Posts: 107
Location: N. Idaho

Posted: Wed Apr 16, 2008 10:57 am Post subject: 503 Teardown Report

Roger, thanks for the comprehensive report.  You mentioned 100 degree EGT

split between cylinders.  Was it 100 at full power and 100 at cruise, or

what?



I ask because I just noticed that my 503 is 100 degrees hotter EGT on one

than the other at full throttle, but only about 35 degrees split at

cruise.  I also have oil leaking from the back of the low-time engine

(reportedly 25 hrs since new).  I was wondering if this could be the same

thing.



I bought the plane last fall and only have about 20 hours on the low-time

Rotax 503.  It's my first Rotax so I'm not very familiar with it.




. . . This was traced to

a slight leak in the front crank seal that was leaning the mixture to the

front cylinder slightly.  The resulting difference in EGT's had grown

slowly to 100 deg

_________________
Jim
N. Idaho

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Apr 16, 2008 12:53 pm Post subject: 503 Teardown Report

> I have seen a few questions about the 503 on the list lately.  I just 

finished tearing down my 503 after 452.0 hrs of trouble-free service, so I 

thought I would pass along my data.

 > Roger in Oregon

Roger:



Make sure you get it back together in time to fly at Larry's next month.



john h - Patiently waiting for time to depart for MV.

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

R. Hankins

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

Posted: Wed Apr 16, 2008 2:41 pm Post subject: Re: 503 Teardown Report

John:

I would have it together already if I had not done business with CPS in California.  They backordered a bunch of stuff, after telling me it was in stock.  I found out when things didn't arrive. The wrist-pins they sent me had fingerprints rusted into them.  They suggested "scotch brighting" the rust off and then using them.  (No I'm not kidding!) Needless to say I sent them back and have ordered all backordered items elsewhere.  I will not conduct business with them again.  I thought that I could save time because they are only two shipping zones away, but ended up adding two weeks to my rebuild. Doh!  My advice to anyone on this list is to avoid CPS like the plague.



If all goes well, I will have two weekends to run-in and test-fly before heading to the Rock House.  Lord willin' and the creek don't rise I'll make it!

_________________
Roger in Oregon
1992 KXP 503 - N1782C

R. Hankins

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

Posted: Wed Apr 16, 2008 2:51 pm Post subject: Re: 503 Teardown Report

Jim:

The difference between EGT readings did vary with throttle setting.  I was always able to find a spot in the upper to middle cruise range where they would get within 40-50 degrees or so.  The oil leak began as part of a drop every few hours and was starting to streak back along the bottom of the engine the last couple of hours.  If all I ever did was fly the pattern or around farm fields and flatlands, I would have put this off 'til November, but desert canyons and coastal mountain ridges are not very forgiving.  My advice is "when in doubt, change it out."  At my wife's suggestion I am going to start putting away a little each month for an engine rebuild fund.  If the 503 lasts long enough, I may be able to switch to an HKS somewhere down the road.

_________________
Roger in Oregon
1992 KXP 503 - N1782C

John Hauck

Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

Posted: Wed Apr 16, 2008 3:17 pm Post subject: 503 Teardown Report

They suggested "scotch brighting" the rust off and then using them.  (No 

I'm not kidding!)  >

 	  Quote: 	
		   --------

 Roger in Oregon


	




Roger:



Great news!



I quit doing business with CPS and LEAF many, many years ago for very 

similar reasons.



Recommend South Mississippi Light Aircraft, Ronnie Smith, Lucedale, MS.  He 

can probably get stuff to you all as quickly as any of the other ROTAX 

service centers.



john h

mkIII

_________________
John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama

Dwight

Joined: 21 Feb 2008
Posts: 12
Location: Illinois

Posted: Wed Apr 16, 2008 7:39 pm Post subject: Re: 503 Teardown Report

Sounds like you are burning very clean.  I have a question regarding the Marvel.  Is the 2 oz of Marvel substituted for 2 oz of the Pennzoil in the mix, or added in on top of the 50 to 1 mix?



Thanks,

Dwight

R. Hankins

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

Posted: Wed Apr 16, 2008 9:38 pm Post subject: Re: 503 Teardown Report

Dwight:

I add the Marvel in addition to the 50:1 mix of two stroke oil.  I can't say for sure that the Marvel is what kept my engine clean, but I can state with confidence that it didn't do it any harm.

_________________
Roger in Oregon
1992 KXP 503 - N1782C

gaman(at)att.net
Guest

Posted: Thu Apr 17, 2008 5:01 am Post subject: 503 Teardown Report

Just a thought here on alcohol.My tester is a test tube with graduations on it .Fill to about 1 inch with water,add fuel to the top line and shake.The water line has 3 or 4 marks above it marked in percentages of alcohol.That water line rises according to the amount of alcohol in it after it sets a minute or two.It,s a Briggs & Stratton fuel tester.If I put a pint of water in 5 gallons of fuel ,shook it up ,let stand then poured it thru a water separating funnel,would it effectively remove the alcohol,without removing any additives or change anything else?



---

Dwight

Joined: 21 Feb 2008
Posts: 12
Location: Illinois

Posted: Thu Apr 17, 2008 7:02 am Post subject: Re: 503 Teardown Report

I've heard of doing that, but by draining off the separated water first with a siphon.  Maybe then pour thru the Mr Funnel to get the last little bit.

BUT, heres the problem the way I see it.  The ethanol is put there not just as a filler (to make the tree huggers and corn farmers happy) but it also boost the octane.  So lets just say the basic mix of 10% ethanol enhanced fuel is maybe only 84? octane before they mix in the ethanol.  The ethanol brings the octane up to the min requirement of 87 without using lead or other more expensive additives to the blend.  When you remove it, the octane is going back down, plus you have 9/10 of the gallon of fuel you paid for, and a mess to dispose of.  Anyone out there in the refinery business that could shed some light on this?



Dwight

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