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dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Tue Jun 16, 2009 9:37 pm Post subject: Rotax 503 running problem

I have not yet figured out what is wrong with my friends single carb dual ignition Rotax 503

 It recently developed a problem, I am not sure exactly when it happened so it is hard for me to say it happened when this happened to the plane or motor.

When he first got it it reved over 7,000 rpm at partial throttle, an immediate re pitch was in order. I had him add about 3 degrees to the 3 blade prop. On the ground it was about 6,000.

He flew it and the motor acted up so he landed. I Found it ran on one ignition and not the other. Fouled plugs were found. 

The case was made that it is OK to lean out your 2stroke airplane, even necessary at times. 

Idle was OK but just above idle was pretty rich. I installed a smaller needle jet in the VM Mikuni carb. Idle improved, (it is the smoothest idlingg Rotax 503 I have heard) cruise sounded better and fuel burn dropped to about 2.5 gallons per hour.

 I dropped the main jet a couple sizes and things got better on top.

In monument Valley I may have dropped the main jet and played with an air screw. Greg's plane seemed on par with mine. 

Well back in Phoenix I heard Greg's plane and it sounded off. He said it would not rev.

Greg found oil on his prop, it was from a leaking head gasket, which  was from not one but 2 broken cylinder studs. After fixing that the problem remained

Here is what I have found so far.

 With a CHT of 200 I apply full throttle and the motor revs to 6000 (static) after the motor hits about 225 it starts to slow. 

By the time I near 300 it won't rev past about 5,200. 

If I kill ignition 1 it rev to 4,800. 

If I kill only ignition 2, it revs to 4,300. 

If I change the main jet either way it losses power. 

At idle Ignition 1 killed results in 2,000 rpm while killing only ignition 2 results in about 2,100 rpm idle. 

The plugs look fine, the resistance values of the caps look good. 

The motor runs smooth. The full throttle EGT looks low 900 but leaner main jet reduces rpm and richer makes it run rough. 

Main jet changes are seen on the EGT. 

Ring end gap looks to be about .015 inch. 

Carbon buildup looks to be in remission. 

The motor is running 50:1 on the oil, I run 32:1 with the same oil and have about 90 hours on my plugs. 

I get the highest EGT when I open the throttle to get about 4,200 rpm and can get a little over 1,000 EGT with CHT below 300.

 There is no evidence of detonation on the piston or the plugs, the burn back is not real distinct but seems quite safe.

I will test the secondary required voltage and see if I get anywhere with that.

I am not looking for your basic doctorate dissertation assembled by someone that has never tuned a 2 cycle engine. 

prefer to keep it practical and applicable. 

No Time Area Per Unit of Displacement, Brake Mean Effective Pressure, or squish velocity theory needed here.

Mechanically the motor feels normal.

More or less fuel makes things worse.

Makes me lean toward electrical.

Has anyone seen this kind of thing before?

It is not plugs as changing the plug wires around on the plugs made no difference in how it ran under any condition. 

Any ideas would be appreciated.

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

aslsa.rng(at)gmail.com
Guest

Posted: Wed Jun 17, 2009 4:03 am Post subject: Rotax 503 running problem

Dale,

Easiest advice, no theory involved, borrow a stock jetted Bing carb and air cleaner off a known to run good single carb 503 and swap it for the Mikuni. You'll probably have to change out throttle and choke cables, etc, and yes, this will be a PITA.

 Check the exhaust system for 

Rick



On Wed, Jun 17, 2009 at 12:37 AM, dalewhelan <dalewhelan(at)earthlink.net (dalewhelan(at)earthlink.net)> wrote:

 [quote]--> Kolb-List message posted by: "dalewhelan" <dalewhelan(at)earthlink.net (dalewhelan(at)earthlink.net)>

  

 I have not yet figured out what is wrong with my friends single carb dual ignition Rotax 503

  It recently developed a problem, I am not sure exactly when it happened so it is hard for me to say it happened when this happened to the plane or motor.

 When he first got it it reved over 7,000 rpm at partial throttle, an immediate re pitch was in order. I had him add about 3 degrees to the 3 blade prop. On the ground it was about 6,000.

 He flew it and the motor acted up so he landed. I Found it ran on one ignition and not the other. Fouled plugs were found.

 The case was made that it is OK to lean out your 2stroke airplane, even necessary at times.

 Idle was OK but just above idle was pretty rich. I installed a smaller needle jet in the VM Mikuni carb. Idle improved, (it is the smoothest idlingg Rotax 503 I have heard) cruise sounded better and fuel burn dropped to about 2.5 gallons per hour.

   I dropped the main jet a couple sizes and things got better on top.

 In monument Valley I may have dropped the main jet and played with an air screw. Greg's plane seemed on par with mine.

 Well back in Phoenix I heard Greg's plane and it sounded off. He said it would not rev.

 Greg found oil on his prop, it was from a leaking head gasket, which  was from not one but 2 broken cylinder studs. After fixing that the problem remained

 Here is what I have found so far.

  With a CHT of 200 I apply full throttle and the motor revs to 6000 (static) after the motor hits about 225 it starts to slow.

 By the time I near 300 it won't rev past about 5,200.

 If I kill ignition 1 it rev to 4,800.

 If I kill only ignition 2, it revs to 4,300.

 If I change the main jet either way it losses power.

 At idle Ignition 1 killed results in 2,000 rpm while killing only ignition 2 results in about 2,100 rpm idle.

 The plugs look fine, the resistance values of the caps look good.

 The motor runs smooth. The full throttle EGT looks low 900 but leaner main jet reduces rpm and richer makes it run rough.

 Main jet changes are seen on the EGT.

 Ring end gap looks to be about .015 inch.

 Carbon buildup looks to be in remission.

 The motor is running 50:1 on the oil, I run 32:1 with the same oil and have about 90 hours on my plugs.

 I get the highest EGT when I open the throttle to get about 4,200 rpm and can get a little over 1,000 EGT with CHT below 300.

  There is no evidence of detonation on the piston or the plugs, the burn back is not real distinct but seems quite safe.

 I will test the secondary required voltage and see if I get anywhere with that.

 I am not looking for your basic doctorate dissertation assembled by someone that has never tuned a 2 cycle engine.

 prefer to keep it practical and applicable.

 No Time Area Per Unit of Displacement, Brake Mean Effective Pressure, or squish velocity theory needed here.

 Mechanically the motor feels normal.

 More or less fuel makes things worse.

 Makes me lean toward electrical.

 Has anyone seen this kind of thing before?

 It is not plugs as changing the plug wires around on the plugs made no difference in how it ran under any condition.

 Any ideas would be appreciated.

 

 --------

 Dale Whelan

 503 powered Firestar II

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=248637#248637

 

 

 

 

 

 

 

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 [b]

aslsa.rng(at)gmail.com
Guest

Posted: Wed Jun 17, 2009 4:07 am Post subject: Rotax 503 running problem

Sorry about that, jumpy touch pad on the laptop. As I started to say, Check the exhaust for blockages or part failure internally. 



Rick



On Wed, Jun 17, 2009 at 7:00 AM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:

 [quote]Dale,

Easiest advice, no theory involved, borrow a stock jetted Bing carb and air cleaner off a known to run good single carb 503 and swap it for the Mikuni. You'll probably have to change out throttle and choke cables, etc, and yes, this will be a PITA.

  Check the exhaust system for 

Rick

On Wed, Jun 17, 2009 at 12:37 AM, dalewhelan <dalewhelan(at)earthlink.net (dalewhelan(at)earthlink.net)> wrote:

   	  Quote: 	
		  --> Kolb-List message posted by: "dalewhelan" <dalewhelan(at)earthlink.net (dalewhelan(at)earthlink.net)>

   

 I have not yet figured out what is wrong with my friends single carb dual ignition Rotax 503

  It recently developed a problem, I am not sure exactly when it happened so it is hard for me to say it happened when this happened to the plane or motor.

 When he first got it it reved over 7,000 rpm at partial throttle, an immediate re pitch was in order. I had him add about 3 degrees to the 3 blade prop. On the ground it was about 6,000.

 He flew it and the motor acted up so he landed. I Found it ran on one ignition and not the other. Fouled plugs were found.

 The case was made that it is OK to lean out your 2stroke airplane, even necessary at times.

 Idle was OK but just above idle was pretty rich. I installed a smaller needle jet in the VM Mikuni carb. Idle improved, (it is the smoothest idlingg Rotax 503 I have heard) cruise sounded better and fuel burn dropped to about 2.5 gallons per hour.

    I dropped the main jet a couple sizes and things got better on top.

 In monument Valley I may have dropped the main jet and played with an air screw. Greg's plane seemed on par with mine.

 Well back in Phoenix I heard Greg's plane and it sounded off. He said it would not rev.

 Greg found oil on his prop, it was from a leaking head gasket, which  was from not one but 2 broken cylinder studs. After fixing that the problem remained

 Here is what I have found so far.

  With a CHT of 200 I apply full throttle and the motor revs to 6000 (static) after the motor hits about 225 it starts to slow.

 By the time I near 300 it won't rev past about 5,200.

 If I kill ignition 1 it rev to 4,800.

 If I kill only ignition 2, it revs to 4,300.

 If I change the main jet either way it losses power.

 At idle Ignition 1 killed results in 2,000 rpm while killing only ignition 2 results in about 2,100 rpm idle.

 The plugs look fine, the resistance values of the caps look good.

 The motor runs smooth. The full throttle EGT looks low 900 but leaner main jet reduces rpm and richer makes it run rough.

 Main jet changes are seen on the EGT.

 Ring end gap looks to be about .015 inch.

 Carbon buildup looks to be in remission.

 The motor is running 50:1 on the oil, I run 32:1 with the same oil and have about 90 hours on my plugs.

 I get the highest EGT when I open the throttle to get about 4,200 rpm and can get a little over 1,000 EGT with CHT below 300.

  There is no evidence of detonation on the piston or the plugs, the burn back is not real distinct but seems quite safe.

 I will test the secondary required voltage and see if I get anywhere with that.

 I am not looking for your basic doctorate dissertation assembled by someone that has never tuned a 2 cycle engine.

 prefer to keep it practical and applicable.

 No Time Area Per Unit of Displacement, Brake Mean Effective Pressure, or squish velocity theory needed here.

 Mechanically the motor feels normal.

 More or less fuel makes things worse.

 Makes me lean toward electrical.

 Has anyone seen this kind of thing before?

 It is not plugs as changing the plug wires around on the plugs made no difference in how it ran under any condition.

 Any ideas would be appreciated.

 

 --------

 Dale Whelan

 503 powered Firestar II

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=248637#248637

 

 

 

 

 

 

 

 ===========

 arget="_blank">http://www.matronics.com/Navigator?Kolb-List

 ===========

 http://forums.matronics.com

 ===========

 le, List Admin.

 ="_blank">http://www.matronics.com/contribution

 ===========

 

 

 

 	


 



[b]

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Jun 17, 2009 6:10 am Post subject: Rotax 503 running problem

At 10:37 PM 6/16/09 -0700, you wrote:

 	  Quote: 	
		  



I have not yet figured out what is wrong with my friends single carb dual ignition Rotax 503


	


Dale,



Points or CD ignition?  If it has points, the points may be floating due to 

weak return springs or a sticky pivot.



Might be a fuel flow restriction.  Check for dirt just ahead of the float 

needle valve orifice, plugged fuel filter, cracked fuel or crankcase to pump 

line, broken valve in fuel pump.



FWIW



Jack B. Hart FF004

Winchester, IN

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Wed Jun 17, 2009 7:05 am Post subject: Re: Rotax 503 running problem

 	  dalewhelan wrote: 	
		  I have not yet figured out what is wrong with my friends single carb dual ignition Rotax 503

 It recently developed a problem, I am not sure exactly when it happened so it is hard for me to say it happened when this happened to the plane or motor.

When he first got it it reved over 7,000 rpm at partial throttle, an immediate re pitch was in order. I had him add about 3 degrees to the 3 blade prop. On the ground it was about 6,000.

He flew it and the motor acted up so he landed. I Found it ran on one ignition and not the other. Fouled plugs were found. 

The case was made that it is OK to lean out your 2stroke airplane, even necessary at times. 

Idle was OK but just above idle was pretty rich. I installed a smaller needle jet in the VM Mikuni carb. Idle improved, (it is the smoothest idlingg Rotax 503 I have heard) cruise sounded better and fuel burn dropped to about 2.5 gallons per hour.

 I dropped the main jet a couple sizes and things got better on top.

In monument Valley I may have dropped the main jet and played with an air screw. Greg's plane seemed on par with mine. 

Well back in Phoenix I heard Greg's plane and it sounded off. He said it would not rev.

Greg found oil on his prop, it was from a leaking head gasket, which  was from not one but 2 broken cylinder studs. After fixing that the problem remained

Here is what I have found so far.

 With a CHT of 200 I apply full throttle and the motor revs to 6000 (static) after the motor hits about 225 it starts to slow. 

By the time I near 300 it won't rev past about 5,200. 

If I kill ignition 1 it rev to 4,800. 

If I kill only ignition 2, it revs to 4,300. 

If I change the main jet either way it losses power. 

At idle Ignition 1 killed results in 2,000 rpm while killing only ignition 2 results in about 2,100 rpm idle. 

The plugs look fine, the resistance values of the caps look good. 

The motor runs smooth. The full throttle EGT looks low 900 but leaner main jet reduces rpm and richer makes it run rough. 

Main jet changes are seen on the EGT. 

Ring end gap looks to be about .015 inch. 

Carbon buildup looks to be in remission. 

The motor is running 50:1 on the oil, I run 32:1 with the same oil and have about 90 hours on my plugs. 

I get the highest EGT when I open the throttle to get about 4,200 rpm and can get a little over 1,000 EGT with CHT below 300.

 There is no evidence of detonation on the piston or the plugs, the burn back is not real distinct but seems quite safe.

I will test the secondary required voltage and see if I get anywhere with that.

I am not looking for your basic doctorate dissertation assembled by someone that has never tuned a 2 cycle engine. 

prefer to keep it practical and applicable. 

No Time Area Per Unit of Displacement, Brake Mean Effective Pressure, or squish velocity theory needed here.

Mechanically the motor feels normal.

More or less fuel makes things worse.

Makes me lean toward electrical.

Has anyone seen this kind of thing before?

It is not plugs as changing the plug wires around on the plugs made no difference in how it ran under any condition. 

Any ideas would be appreciated. 	




Here's what you want to see on the 503:



WOT rpm on climbout: 6300 to 6500.

Cruise rpm: 5200-5500. above 5500 I wouldn't recommend for extended periods of time and 6000+ continuous is too much indicating underpropping or simply running too hard.



CHT: 300F nominal. Engine should sit between 290 and 310F indicated at cruise. Shouldn't exceed 320-30 except in long full power climbs of more than a minute or two, then you don't want to see more than 350F (new engine will run about 330F cruise for about the first 10 hours, then it'll settle down to about 300).



EGT: 1000-1050F at wide open of 6300 to 6400rpm. 900 is too low, 1100F is still kind of ok, but approaching the edge. Cruise EGT's should sit around 1050 to 1100F. 1150F is still ok, but also getting near the edge meaning either slightly too lean or underpropped (or both), below 1050F usually means too rich or overpropped or both.



Oil: 50:1 _ONLY_. Do NOT run higher concentrations of oil like 32:1. This will put you down in a field after a while. The coking of the motor will stop the prop if the too-lean mixture doesn't beat it to it.



After all that, I'd check the following mechanical things:



- did the repair on the head gaskets take? If they've been loose for a while, the gasket or even the head can become deformed such that you may not get a good seal even with proper torquing of the nuts.



- check for leaky crank seals at both ends. A thick kind of goo is more or less normal after about the first 50 to 60 hours, tho not real good, and a thin fluid means a teardown/reseal is needed.



- check for scuffing on the piston skirt through both the exhaust and intake ports. A minor siezure can cause all kinds of wierd running problems like hesitation, etc.



- as others have suggested, try fitting a known-good Bing to the engine to rule out a carburettor problem.



It's a pretty simple motor so troubleshooting isn't that hard... Let us know how it goes...



LS

_________________
LS
Titan II SS

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Wed Jun 17, 2009 9:50 am Post subject: Re: Rotax 503 running problem

Thanks for the input guys. some thoughts:

I had it running quite well on the Mikuni perhaps 6 hours.

I will find out if it is point or CDI, I assumed with dual ignition and coils like my DCDI motor it was CDI

I have 100 hour on my plane with 32:1 oil and have less carbon in the motor than Greg's plane at 50:1 The Spark plugs also look better than his and have 90 hours on them.

Leaking head gasket has been repaired.

While more oil leans the mixture it is negligible and tunable. the difference in fuel is less than 1 %  in this case well under half a jet size, and the oil is almost double.

I will do a leakdown test but the motor does not seem to me to be acting that way.

Will check piston condition but I don't think that is it, but I don't know what the problem is yet.

It is not fuel starvation, I went up 50% on the main and it ran rich, rough, and low RPM.

The plugged exhaust systems I have dealt with never let the motor rev, this motor revs and holds it for a short time then drops. Once the motor cools the process repeats.

I don't think I will see the motor for about 2 weeks, I will share with you guys what was wrong weather you folks find the problem or I do.

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Wed Jun 17, 2009 11:17 am Post subject: Re: Rotax 503 running problem

 	  dalewhelan wrote: 	
		  Thanks for the input guys. some thoughts:

I had it running quite well on the Mikuni perhaps 6 hours.

I will find out if it is point or CDI, I assumed with dual ignition and coils like my DCDI motor it was CDI

I have 100 hour on my plane with 32:1 oil and have less carbon in the motor than Greg's plane at 50:1 The Spark plugs also look better than his and have 90 hours on them.

Leaking head gasket has been repaired.

While more oil leans the mixture it is negligible and tunable. the difference in fuel is less than 1 %  in this case well under half a jet size, and the oil is almost double.

I will do a leakdown test but the motor does not seem to me to be acting that way.

Will check piston condition but I don't think that is it, but I don't know what the problem is yet.

It is not fuel starvation, I went up 50% on the main and it ran rich, rough, and low RPM.

The plugged exhaust systems I have dealt with never let the motor rev, this motor revs and holds it for a short time then drops. Once the motor cools the process repeats.

I don't think I will see the motor for about 2 weeks, I will share with you guys what was wrong weather you folks find the problem or I do. 	




The only time I've seen a heavier mixture than 50:1 utilized was in the 582 in a helicopter application - 40:1 was recommended due to the continuous high power operation, but the engine exhibited a higher than normal failure rate anyway.



At 32:1, I'd increase the teardown/cleanup schedule for sure. There's no good reason that I can think of to run that much oil, well, under any circumstances....



LS

_________________
LS
Titan II SS

jbhart(at)onlyinternet.ne
Guest

Posted: Wed Jun 17, 2009 12:10 pm Post subject: Rotax 503 running problem

At 10:50 AM 6/17/09 -0700, you wrote:

 	  Quote: 	
		  



Dale,
	




One last thought.  If carbon builds up under the rings, it will cause the 

problem you describe.  I had this problem with a 447.  What happens is the 

rings heat up and try to expand but the slot depth is not available for them 

to contract back into.  As result the ring then presses more against the 

cylinder wall and increases ring to cylinder wall friction.  If you checked 

the ring in the cylinder clearance did you clean out the slots?



Jack B. Hart FF004

Winchester, IN

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Wed Jun 17, 2009 7:03 pm Post subject: Re: Rotax 503 running problem

Lucien wrote



At 32:1, I'd increase the teardown/cleanup schedule for sure. There's no good reason that I can think of to run that much oil, well, under any circumstances....



LS[/quote]

With 90 hours on the plugs and a combustion chamber that is clean, my motor disagrees with you, as do I.

I am not sure if you realize it but while some of what you wrote holds truth, the way it sounds reminds me of a wannabe cowboy in a hole in the wall bar in some city trying to pick a fight with someone who is just there to have a good time. Perhaps I am just taking it wrong, but I have read similar sounding responses to other forum members. Either way, perhaps I can set you straight.

If I misinterpreted your tone I do apologize.

So a little about me.

Please understand, I have lots to learn, but I have made a living for the past 28 years fixing many forms of internal combustion motors. 

I have spent 15 years teaching the repair of Motorcycles.

I am a Honda registered technician.

I have taught Suzuki dealership personnel for American Suzuki.

I have repaired Leaf blowers, chain saws, lawn mowers, go carts, cars, boats, jetskis, motorcycles, generators, snowmobiles, all terrain vehicles, and airplanes.

I have also spent 25 years in motorsports competition, some of that at the professional level. 

I have done all of my own machine preparation with the exception of cylinder porting, re-plating, and combustion chamber reshaping.

Although I read much, I am not sharing with you what I have read, I am sharing what I have found over years of testing and competition.



After Having conducted considerable dyno testing I can tell you exactly why I would in some conditions run more than 50:1.

Reason 1 More Horsepower.

Reason 2 Improved engine longevity

Over simplification could go like this: no oil = no lubrication, Some oil= some lubrication, More oil = more lubrication. 

Of course there are practical limitations. 

I gained over 3% on a 76 HP 250 cc racing engine by changing from 32:1 to 20:1. My pipes and plugs are drier than those who run less oil and don't know how to tune a 2 stroke. 

That same 250cc racing motor develops 86 HP today.

The only place it develops carbon is the first 6 inches of the head pipe and a very thin amount on the piston crown, the head wipes lean.

My friend did a long term test on a motocross 250 2 stroke and saw a 30% increase in motor life by increasing the amount of oil he ran.

I can tell you why I would run little oil.

Less burned oil in the air or water in the case of boats.



The ring land idea sound worth looking into, the plane is a recent purchase and was running so rich it would short plugs in under 10 hours. Every thing you can see with the heads removed looks good to me but I did not look through any ports or remove cylinders.



I guess it won't be a quick field fix, I may have to get serious.

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

Last edited by dalewhelan on Wed Jun 17, 2009 11:24 pm; edited 1 time in total

WhiskeyVictor36(at)aol.co
Guest

Posted: Wed Jun 17, 2009 7:43 pm Post subject: Rotax 503 running problem

In a message dated 6/17/2009 1:51:33 P.M. Eastern Daylight Time,  dalewhelan(at)earthlink.net writes:

  	  Quote: 	
		     <this motor revs and holds it for a short time then drops. Once    the motor cools the process repeats.>

    Dale,

    

   FWIW

    

   The above comment describes a seizure in process.     Engine heats up, piston(s) expand and get tight in cylinder bore, so RPM's    drop.  The engine cools, piston(s) shrink and get loose, then RPM's    increase.

    

   <Two cylinder stud bolts were broken.>

    

   What caused them to be broken?  I just saw a video on 503    rebuild and they cautioned that when tightening the head bolts (nuts), make    sure to tighten each equally.  That is, if one is tightened too much    (even finger tight) before the others, it can tip the head over to one    side.  Then when the others are tightened, it can cause the bolts to    break, or stretch to break later.  Might even cause damage to the head    gasket and/or surface.

    

   Bill    Varnes

Original Kolb FireStar

Audubon NJ

Do Not  Archive

	


 <?redir=http:%2F%2Fad.doubleclick.net%2Fclk%3B215692145%3B38015538%3Bh>Dell Days of Deals! June 15-24 - A New Deal Everyday!

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Wed Jun 17, 2009 10:58 pm Post subject: Re: Rotax 503 running problem

Whiskeyriver 

Thanks for the reply



The above comment describes a seizure in process. Engine heats up, piston(s) expand and get tight in cylinder bore, so RPM's drop. The engine cools, piston(s) shrink and get loose, then RPM's increase.



I thought that, richened the mixture and it acted the same.

I also doubled the oil, acted the same.

 I removed the rear head and looked at the bore with piston at BDC, No score marks 

Should have a look at the front.

I rotated the motor after shut down, felt fine.



As for the broken studs,

One had rust at the break indicating it had been broken for some time. 

Greg does not keep a log or have an hour meter in the plane, I suspect he has flow it less than 20 hours since he got it.

I have not yet convinced him to fix it before it breaks so he operates on the fix it when it breaks principle to some extent. He had not touched the motor except for spark plugs and installing EGT CHT

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 18, 2009 2:46 am Post subject: Re: Rotax 503 running problem

 	  dalewhelan wrote: 	
		  

With 90 hours on the plugs and a combustion chamber that is clean, my motor disagrees with you, as do I. 	




You do know the 503 is a Dykes ring design right? And that its primary use is on _airplanes_ not bikes? How many 503's have you run to TBO at 32:1? How many past TBO at 32:1? It'd be good to review your experience on this, could be very helpful to the rest of us who've been hanging underneath this motor for years and years and been doing it wrong all this time.



You said you have a lot to learn - well, yeah, I'd say that you do. And I hope you learn it without having to put down in a field when the fan stops turning, or advise someone else into doing the same. I'll have one more go here and hope it takes. After that, it's your motor and your plane.



If you really have the mechanical experience you say you do, you know the value of field experience with an engine - with the 503 we got lots of it, decades in fact, and it all points to _50:1 only_, no other ratio when running premix. More oil, especially at the level of 32:1, is taking chances you don't need to take, much like the suggestion of running 6500 rpm all the time. 



But it's your plane and motor. Let's all be careful out there including where we get our advice.



Good luck,



LS

_________________
LS
Titan II SS

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Thu Jun 18, 2009 8:44 am Post subject: Re: Rotax 503 running problem

[quote="lucien"] 	  dalewhelan wrote: 	
		  

With 90 hours on the plugs and a combustion chamber that is clean, my motor disagrees with you, as do I. 	




You do know the 503 is a Dykes ring design right? 

Of course I do

And that its primary use is on _airplanes_ not bikes?

Actually the primary use is low RPM boat motors and some motorcycles. Specifically used because of the better sealing at low RPM because of the higher cylinder contact surface area. While they have Less tendency to flutter at high RPM than a conventional or Keystone ring They are not generally used in High RPM motors due to the increased friction their surface area provides against the cylinder.



 How many 503's have you run to TBO at 32:1? 

None yet I got mine at TBO and have flown it 100 hours.

How many past TBO at 32:1? 

I am 100 past TBOon my first 503 How many times have you had to tune a motor and have it compared against the best tuners in America?

It'd be good to review your experience on this, could be very helpful to the rest of us who've been hanging underneath this motor for years and years and been doing it wrong all this time.

Sarcasm, something I have been told I am very good at, I have trouble not using it myself. My grandma used to cut the ends off the roast before she cooked it, so did my mom, mom did it because her mom did. Grandma did it to make it fit in the pan. Not saying you are stupid or wrong, just saying there may be something you do not know about.



You said you have a lot to learn 

Thinking you  know it all means the end of progress and to me the opportunity to get taught the hard way that you don't know it all. - well, yeah, I'd say that you do. And I hope you learn it without having to put down in a field when the fan stops turning, 

Funny, it seems that my background may be discomforting to you, The advice I get is don't touch it you'll break it. Don't lean it you'll die. These same people land and there plane won't restart hot using and electric starter. Mine starts with one tug of the recoil started. In the morning I pull it 3 times and watch them try to light off before the battery dies. They too have been hanging under a 503 for many years. I found my flight instructors plane to be opening the throttle only part way from the front, and I told him how to fix his charging system. or advise someone else into doing the same. I'll have one more go here and hope it takes. After that, it's your motor and your plane.



If you really have the mechanical experience you say you do, 

That statement sounds like you are calling me a liar, hope you did not mean it that way.

you know the value of field experience with an engine 

There is much truth to what you say sadly I have seen many Harley mechanics that think this way, my motor is so much different than any other motor that operates on the suck squeeze bang blow method No one else but me can make the thing run at all, ever notice how bad some of those sound? The fact is many people working on motors are not mechanics and all they can really do is try to copy what they think a mechanic does.

- with the 503 we got lots of it, decades in fact, and it all points to _50:1 only_, no other ratio when running premix. 

What ratios have you tried and what were your results? How did it do at 40:1 and what specific problems did you have? What were the specific result of 60:1

More oil, especially at the level of 32:1, is taking chances you don't need to take, 

How so, what chances am I taking? The oil coking you mentioned in an earlier post does not make sense to me, I have been told( By a technical service manager at American Suzuki and a former Spectro employee) that oil coking was a result of high oil temps, they had a problem with it when people left air cooled ATVs idling for long period of time. The temperature the hit were nowhere close to what a 503 sees. 

much like the suggestion of running 6500 rpm all the time.

I read that post and you may have been in a hurry when you quoted it, you left out how long he said to run it for, the time was 5 minutes, not all the time. When you asked how long he had at 6,500 I thought about my limited time flying and how I would answer that. My answer is about 300 takeoffs X 1 minute and maybe about 100 of those at X about 4 minutes so about 700 minutes. I also thought who would log max power time? 



But it's your plane and motor. 

This sounds like racing to me, I pay for all the choices I make no matter whose advice I take, that is exactly why I experiment and test and learn and practice.

Let's all be careful out there including where we get our advice.

Many people think racer have a death wish, news flash many racers think that of pilots. Both disciplines are very safety conscious, those who are not die, some of those who are die too. Believe it or not I am safety conscious. While a friend of mine calls me Mr Safety I am always trying to improve my safety. even though my ballast does not like it, I always fly solo after working on my plane, 2 reasons, one is an FAR, the other is experience. When we were in Monument Valley my ballast wanted a ride, the density altitude was higher than I had taken off with her before so I had to evaluate the planes performance first. I lean my motor out and people accuse me of trying to go faster (because of my racing background I guess?), the reality is I don't want to run out of gas on a cross country, lower fuel burn gives me a little insurance, too rich fouls plugs, and I want to climb even if I am in sink.



As a side note, when I said I was going to Missouri to get my plane in July and fly it back people told me it was a bad idea, nobody told me why. I now know why. Another pilot/instructor/FBO voiced concerns until he talked and flew with me. He still had concerns but was more comfortable.



Good luck,



Thanks for the reply and I hope I am not boring, or offending anyone.

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 18, 2009 8:57 am Post subject: Re: Rotax 503 running problem

[quote="dalewhelan"] 	  lucien wrote: 	
		  



 How many 503's have you run to TBO at 32:1? 

None yet I got mine at TBO and have flown it 100 hours.

	




That's what I figured. Let us know what your results are when you _do_ get a little more experience with this motor.



Till then, folks, Caveat Emptor.



LS

_________________
LS
Titan II SS

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Thu Jun 18, 2009 9:40 am Post subject: Re: Rotax 503 running problem

I have read many posts, many helpful. It is sad to think that some one with your experience and background habitually expresses himself in a critical, dismissive, and belittling manner.

When you do this fewer people want to hear from you.

I have noticed a couple of people on this site. John is one, I even met him briefly at Monument Valley this year. He came over and said hi, he talked with Greg about his nose gear Firestar, He took local kids for rides, he tries to help us newbies on this forum. He seems like a kind and respectable man. I read posts where it looked like you twisted what he said and ridiculed him. I expected you to do the same with me and you seem to have fulfilled that promise. I like it when people try to help others, I am disappointed when I see criticism offered when help is asked for. It is a shame that with your greater life experience and greater flying experience that I longer wish to hear what you have to say. You probably have a lot to offer and could be a great mentor, I think you prefer not to do that. Please don't offer me your type of help any longer.

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

pj.ladd(at)btinternet.com
Guest

Posted: Thu Jun 18, 2009 10:24 am Post subject: Rotax 503 running problem

503 we got lots of it, decades in fact, and it all points to _50:1 only_, no 

other ratio when running premix. >>



Why do some pilots always disagree with the manufacturer? You would have 

though that it was a safe assumption that the makers have data at their 

fingertips which is not generally available to the average pilot. They have 

the correlated results of every engine they have ever made. Even the most 

enthusiastic pilot has only his own experience or maybe `say so` gleaned 

from a local `expert`.



 	  Quote: 	
		  From some of the posts it seems that there are pilots constantly changing 

jets, renewing carb. needles, leaning the settings etc. Why not just leave 
	


well alone.

Running an engine with lower oil in the mix strikes me as being foolish. 

What is the object? Saving money?



Some people are just of a nature that they love pulling engines apart and 

experimenting. Fair enough, its a lot of fun if you are that way inclined 

but I don`t think that individual experience outweighs the accumulated info. 

which a manufacturer has.



Cheers



Pat

lucien

Joined: 03 Jun 2007
Posts: 721
Location: santa fe, NM

Posted: Thu Jun 18, 2009 12:45 pm Post subject: Re: Rotax 503 running problem

 	  pj.ladd(at)btinternet.com wrote: 	
		  

well alone.

Running an engine with lower oil in the mix strikes me as being foolish. 

What is the object? Saving money?



Some people are just of a nature that they love pulling engines apart and 

experimenting. Fair enough, its a lot of fun if you are that way inclined 

but I don`t think that individual experience outweighs the accumulated info. 

which a manufacturer has.



Cheers



Pat 	




It's worth noting that the 50:1 requirement is originally Rotax's requirement and it still is. 

There are some mistakes here and there in the 2-stroke manuals (such as the infamous max CHT limit) but the rest is reliable for sure, including the premix oil ratio.



I like to let the other guys do the experimenting as I generally can't afford the mishaps, dealing with FSDO and FAA, etc., that come from going it on your own and ignoring correct advice. So I just tow the line on what we know to be the most reliable running configuration, rpms, installation, etc. and fly instead....



LS

_________________
LS
Titan II SS

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Thu Jun 18, 2009 6:08 pm Post subject: Re: Rotax 503 running problem

Not that this was the intent of this thread but, Is there anyone on this board other than myself that has tried running more than the recommended  amount of oil and willing to share with me what they found.

Just for fun, even though I have no inclination to do so, is there anyone on this board that has run less oil than 50:1, ( I once saw a company claim you could run their oil at 150:1) If so would you share your results with me?

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

captainron1(at)cox.net
Guest

Posted: Thu Jun 18, 2009 8:43 pm Post subject: Rotax 503 running problem

To oil ratio I think giving it a bit more oil will improve its reliability. There is of course a point where the oil is detrimental. For example the octane level may (?) start dropping and rapidly ( I need more data on that though, as the oil may have somewhat of a retardant effect on burning efficiency thus preventing detonation), burning efficiency starts falling and so on. But with some experimentation I suppose I can find that point just before the decreased ratio is becoming detrimental. At 35 / 1 the Cyuna seems happy so far. I may try later to 30 to 1 and see if its good. I guess I could try 15-1 on the ground only and see what happens just for the curiosity of it, but oil is more expensive than 91 octane so I guess you can wonder if there is any point to it, to make more smoke and less power. Once you reach the point where the motor gets all the lube it needs then we ain't doing it anymore good tossing more oil into it. 

We just need to be careful.



Ron (at) KFHU



==========================

---- dalewhelan <dalewhelan(at)earthlink.net> wrote: 



=============




Not that this was the intent of this thread but, Is there anyone on this board other than myself that has tried running more than the recommended  amount of oil and willing to share with me what they found.

Just for fun, even though I have no inclination to do so, is there anyone on this board that has run less oil than 50:1, ( I once saw a company claim you could run their oil at 150:1) If so would you share your results with me?



--------

Dale Whelan

503 powered Firestar II





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 49046#249046



--

kugelair.com

dalewhelan

Joined: 11 Nov 2008
Posts: 105
Location: USA ARIZONA fountain hills

Posted: Thu Jun 18, 2009 11:45 pm Post subject: Re: Rotax 503 running problem

I will share what I have found, if you want more contact me off list to reduce drama, I can call you if you like.

[quote="captainron1(at)cox.net"]To oil ratio I think giving it a bit more oil will improve its reliability. There is of course a point where the oil is detrimental. 

More oil can cause problems if the motor is run at too low an RPM, like on final, or prolonged idling. If the motor is jetted rich it will cause more problem so I have had to have the jetting right on all circuits.

For example the octane level may (?) start dropping and rapidly ( I need more data on that though, as the oil may have somewhat of a retardant effect on burning efficiency thus preventing detonation), burning efficiency starts falling and so on. 

There is a way to look at the plugs to see how close to detonation a motor is, you can't easily read it if you are a few sizes rich. The common variables are Mixture, load, relative air density, and rpm. Others include octane, ignition timing, and  compression ratio.

But with some experimentation I suppose I can find that point just before the decreased ratio is becoming detrimental. 

I have found with fuel testing  on a dyno that the motor makes the most power just before it detonates, changing the fuel octane resulted in no power difference once timing was corrected for the fuel and jetting was correct. When you add oxygenated fuel, well cool things happen to the power. If I publicly told you what octane I use, the lynch mob would come looking for me, funny thing, looking at my instructor plane, it seems to need more octane than mine.

At 35 / 1 the Cyuna seems happy so far. I may try later to 30 to 1 and see if its good. I guess I could try 15-1 on the ground only and see what happens just for the curiosity of it, but oil is more expensive than 91 octane so I guess you can wonder if there is any point to it, to make more smoke and less power.

Gordon Jennings was my inspiration for oil ratio testing, I stopped at 20:1 on my race bike, pipes are dry but it smokes in the pits. He was testing for McCullough I think. He said that the motor kept making more power as he added oil and corrected the tuning until he got to something like 12 or 14:1. At that point power increase was negligible and plug fouling was common.

 Once you reach the point where the motor gets all the lube it needs then we ain't doing it anymore good tossing more oil into it. 

We just need to be careful.

Some people have been kind enough to share some things with me off list, they make some good points. They even gave me reasons for why it could be bad and what to watch for.



Ron (at) KFHU



I will strive to create less drama

Dale Whelan



==========================

--------

Dale Whelan

503 powered Firestar II





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 49046#249046



--

kugelair.com[/quote]

_________________
Dale Whelan
503 powered Firestar II, Luscombe 8A
Projection, A simple and interesting Psychological concept

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