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Rotax 2 stroke

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Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Sun Jul 05, 2009 4:12 am Post subject: Rotax 2 stroke

I own a Kitfox with a 912 but some friends of mine bought a Challenger 2 with a Rotax 530 (52 hp I believe) and are flying around in it with little knowledge of the engine. I am in the same boat as I have concentrated on my 912 and know nothing about two strokes (except I liked the one on my 1962 Saab 96 I used to have)

  I went flying in the Challenger the other day and really enjoyed the flight and the smoothness of the engine. It was the only time I have been in front of a two stroke. I know they have a dubious reputation if not treated correctly and was wondering if some of you guys can give me some short tips as to the proper care and feeding of the engine which I could pass on. As an example, when the pilot I was flying with pulled the power back on descent, the EGT red warning light came on warning of exceeding the red line (or close) The pilot blew that off as a fault, but I am not so sure.

  They plan on going to school on the two stroke (Lockwood,Mississippi Light Aircraft,etc.) but in the mean time, is there anything to watch out for. The engine has about 325 hrs on it .It was torn down and checked prior to purchase and was reported very clean. It runs and starts great! The outside temp this time of year is running close to 100 degrees (it sucks !!!!) You have to put a block of ice on the engines to cool them down for start!

  I have a CPS catalog which has super info on the two strokes and will give that to them but I thought perhaps some tips from guys with real real experience would be useful until they get to school.

                                Thanks !!

                                                        Dick Maddux

                                                        Kitfox 4

                                                        Rotax 912 UL

                                                        Milton,Fl  

 Make your summer sizzle with fast and easy recipes for the grill.

  [quote][b]

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lucien

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

Posted: Sun Jul 05, 2009 4:53 am Post subject: Re: Rotax 2 stroke

 	  Dick Maddux wrote: 	
		  I own a Kitfox with a 912 but some friends of mine bought a Challenger 2 with a Rotax 530 (52 hp I believe) and are flying around in it with little knowledge of the engine. I am in the same boat as I have concentrated on my 912 and know nothing about two strokes (except I liked the one on my 1962 Saab 96 I used to have)

  I went flying in the Challenger the other day and really enjoyed the flight and the smoothness of the engine. It was the only time I have been in front of a two stroke. I know they have a dubious reputation if not treated correctly and was wondering if some of you guys can give me some short tips as to the proper care and feeding of the engine which I could pass on. As an example, when the pilot I was flying with pulled the power back on descent, the EGT red warning light came on warning of exceeding the red line (or close) The pilot blew that off as a fault, but I am not so sure.

  They plan on going to school on the two stroke (Lockwood,Mississippi Light Aircraft,etc.) but in the mean time, is there anything to watch out for. The engine has about 325 hrs on it .It was torn down and checked prior to purchase and was reported very clean. It runs and starts great! The outside temp this time of year is running close to 100 degrees (it sucks !!!!) You have to put a block of ice on the engines to cool them down for start!

  I have a CPS catalog which has super info on the two strokes and will give that to them but I thought perhaps some tips from guys with real real experience would be useful until they get to school.

            ï¿½           ï¿½       Thanks !!

            ï¿½           ï¿½            ï¿½           ï¿½      Dick Maddux

            ï¿½           ï¿½            ï¿½           ï¿½      Kitfox 4

            ï¿½           ï¿½            ï¿½           ï¿½      Rotax 912 UL

            ï¿½           ï¿½            ï¿½           ï¿½      Milton,Fl  

 Make your summer sizzle with fast and easy recipes for the grill.

	




Well, you already discovered one of the main operational differences between a 2 and a 4 stroke on that flight 



Namely, a high rpm/closed throttle situation like you commonly have in a descent. This is no problem on a 4-stroke of course and in fact is even kind of good for it, but it's very hard on a 2-stroke. The difficulty being that there's a lack of fuel/oil mixture going through the spinning engine to lubricate it when the throttle is closed and the engine is being windmilled by the prop.



Tips to avoid this situation:

- when descending pull all the way back to idle and descend at lower speeds, i.e. with a max-effort slip or circling, etc. Anything to avoid windmilling the engine with the throttle at reduced or closed settings.



- if you have a C box, fit the rk400 clutch. This offers a complete cure as it disengages the engine from the gearbox completely at idle. Just pull the engine back to idle and you can dive at Vne if you want with no problems.

Not an option on the challenger tho.



Some other operator errors I see with the 2-stroke:



- shock heating, in the form of going immediately to wide open on a cold engine either from not doing an adequate warmup or after a long descent that cools the engine down. A 4-stroke is a fair bit more forgiving of this even tho it's not great practice there either, but the 2-strokes (especially the water cooled like the 582) are not. You can get away with this for a while on the air-cooled, but eventually this will put you down somewhere. On throttle-up, you need to be smooth and gradual if the engine is cool. A good warmup on the ground before takeoff is essential.



- running them too hard. You can't run a 2-stroke like we can run our 912's and other 4-strokes. Those we can basically run as hard as we want for as long as we want long as we don't overspeed them, they'll just laugh at you. You can't do this with a 2-stroke - even the 503 will eventually give up the ghost if run at too high of a throttle setting or too high of an rpm on a continuous basis.



- tweaking and tuning the jetting for the ragged edge of power output. Don't do this - follow the rotax jetting chart to the letter as field experience has shown this to be correct. You need to run rich on the top end, for example, to keep things cool and well lubricated at full power settings.



- underpropping or underpowering. Underpropping leads to an overly lean condition which is a disaster waiting to happen. Underpowering forces you to run too hard (i.e. if you need more than 5800 all the time just to stay in the air, you need a bigger motor or a better prop.



That's most things I can think of off the top of my head. Generally good training is the best medicine on this and it's not too big of a burden on having a good time with a 2-stroke. They'll last a long time and give good service long as you follow the basic guidelines....



LS

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_________________
LS
Titan II SS

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Mon Jul 06, 2009 3:56 am Post subject: Rotax 2 stroke

LS,

  Thank you so much for your tips !!!! I will print this page and pass it to the guys today. They are having so much fun with the plane and I don't want them to ruin their day by having to plant the aircraft in a field with an engine failure ! I remember my old two stroke SAAB had a "free wheeling" devicethat disengaged the engine when you coasted with your foot off the pedal. Now I remember what it was for.

                                                 Dick Maddux

                                                 Milton,Fl

 Looking for love this summer? Find it now on AOL Personals.

  [quote][b]

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lucien

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

Posted: Mon Jul 06, 2009 5:34 am Post subject: Re: Rotax 2 stroke

 	  Dick Maddux wrote: 	
		  LS,

  Thank you so much for your tips !!!! I will print this page and pass it to the guys today. They are having so much fun with the plane and I don't want them to ruin their day by having to plant the aircraft in a field with an engine failure ! I remember my old two stroke SAAB had a "free wheeling" devicethat disengaged the engine when you coasted with your foot off the pedal. Now I remember what it was for.

	




Yep - the rotax 2-strokes aren't among those that just quit or sieze for no reason, so you can expect lots of hours and hours with just fuel/oil and flying with them and very little if any trouble.



A couple other things:

- The CHT figures for the air-cooled motors in the 2-stroke manuals are wrong, off by almost 100F hot. The correct operating range is more like 280-330F and I'd call 350F the max. The 503 when broken-in runs around 300F normally, the 447 around 330 or so. The 447 will hit 350F in a climb easy but the 503 takes effort to get that hot. 



- the most common installation error is too long of a pulse line, the line running from the pulse output on the motor to the pneumatic pump. No longer than a foot and preferably 10" or less is what you want. If this line is too long, no matter what it's made of, the pump won't be driven enough to pump with full effectiveness. You can get totally mysterious fuel starvation events when this line is too long. Often times it is thought that simply using a stiff-walled type of tubing allows a longer length, but the issue is the compliance of the air column in the tubing. Even if the walls are solid steel, if it's too long the pulses will still get absorbed by the air column itself. 



- do NOT use the black automotive line for the pulse line, this is very dangerous. The pleats can separate inside and lead to absorption of the pulses. Don't ask me how I know this. Only use a good tygothane (solid-walled) pulse line here. I'd also recommend tygothane for the entire fuel system.



- the only weakness on the 2-strokes is the crank seals. They start to leak after about 50 to 60 hours, so this requires regular inspection. When you start getting the black fluid collecting under the fan housing, it's time to start planning a teardown/reseal....



LS

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_________________
LS
Titan II SS

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Tue Jul 07, 2009 5:54 pm Post subject: Rotax 2 stroke

I’ve been away for a few days so I expect by now you have many replies...  My advice is twofold.    

   

First get EGT gauges for both cylinders and check by reading the plugs what the correct temperature for your engine is.  

   

Second is to avoid like the plague extended periods of no load running.  Like long descents.  If you have a long decent pull the throttle right back to idle ( where it is naturally richer) and apply a few seconds of climb every thirty seconds or so to prevent the engine from cooling too much.  

   

Noel  

       

From: owner-rotaxengines-list-server(at)matronics.com [mailto:owner-rotaxengines-list-server(at)matronics.com] On Behalf Of Catz631(at)aol.com

 Sent: 05 July 2009 09:30

 To: rotaxengines-list(at)matronics.com

 Subject: Rotax 2 stroke  

  

  

     

I own a Kitfox with a 912 but some friends of mine bought a Challenger 2 with a Rotax 530 (52 hp I believe) and are flying around in it with little knowledge of the engine. I am in the same boat as I have concentrated on my 912 and know nothing about two strokes (except I liked the one on my 1962 Saab 96 I used to have)  

    

 I went flying in the Challenger the other day and really enjoyed the flight and the smoothness of the engine. It was the only time I have been in front of a two stroke. I know they have a dubious reputation if not treated correctly and was wondering if some of you guys can give me some short tips as to the proper care and feeding of the engine which I could pass on. As an example, when the pilot I was flying with pulled the power back on descent, the EGT red warning light came on warning of exceeding the red line (or close) The pilot blew that off as a fault, but I am not so sure.  

    

 They plan on going to school on the two stroke (Lockwood,Mississippi Light Aircraft,etc.) but in the mean time, is there anything to watch out for. The engine has about 325 hrs on it .It was torn down and checked prior to purchase and was reported very clean. It runs and starts great! The outside temp this time of year is running close to 100 degrees (it sucks !!!!) You have to put a block of ice on the engines to cool them down for start!  

    

 I have a CPS catalog which has super info on the two strokes and will give that to them but I thought perhaps some tips from guys with real real experience would be useful until they get to school.  

    

                               Thanks !!  

    

                                                       Dick Maddux  

    

                                                       Kitfox 4  

    

                                                       Rotax 912 UL  

    

                                                       Milton,Fl    

    

       

  

Make your summer sizzle with fast and easy recipes for the grill.  

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

wtmills

Joined: 05 Feb 2007
Posts: 32

Posted: Tue Jul 07, 2009 9:21 pm Post subject: Rotax 2 stroke

Guys -



See the url in the letter pasted below for. I don't operate a two-stroke but have spoken with bh who flew his Kitfox/582 across the Cascades often and without worry. I considered him a two-stroke guru as did others on that list.

 

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

From a "Letter" to EAA Experimenter from Richard Pike, comes the URL for an

interesting article on 2-stroke tuning.  It covers EGT/CHT vs Prop load, and

also color displays of what the spark plugs should look like. 

 

It is "must" reading for all of us 2-strokers. Go to: 

http://www.bcchapel.org/pages/0003/pg11.htm

bh

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



 Bill

On Tue, Jul 7, 2009 at 6:53 PM, Noel <noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)> wrote:

[quote]               

I’ve been away for a few days so I expect by now you have many replies...  My advice is twofold.      

First get EGT gauges for both cylinders and check by reading the plugs what the correct temperature for your engine is.    

 Second is to avoid like the plague extended periods of no load running.  Like long descents.  If you have a long decent pull the throttle right back to idle ( where it is naturally richer) and apply a few seconds of climb every thirty seconds or so to prevent the engine from cooling too much.    

Noel

[b]

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Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Wed Jul 08, 2009 3:24 am Post subject: Rotax 2 stroke

Thanks for the info Noel and Bill. I have copied every piece of info and given it to the guys involved and they are extremly appreciative for the tips!

                                                    Dick Maddux

                                                    Milton,Fl

 Looking for love this summer? Find it now on AOL Personals.

  [quote][b]

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