618 Rotax mag drop

[BrendAn]

When I do a mag check on my 618

One drops 200 rpm but the other one drops about 800 rpm. 

Still seems to run fine at the lower rpm.

Has anyone else had this happen,

Wondering if it's just something to do with the tacho reading being wrong on that circuit.

Other than that the engine runs great. 139 hours.

[facthunter]

Could be a timing variation. Might be worth checking the settings  Something  fitting over each HT wire with the engine running. Keep away from the PROP. Put marks on the prop hub with a marker pen. Nev

[BrendAn]

4 minutes ago, facthunter said:

Could be a timing variation. Might be worth checking the settings  Something  fitting over each HT wire with the engine running. Keep away from the PROP. Put marks on the prop hub with a marker pen. Nev

Can you adjust the timing on them. Never thought of that.

[facthunter]

With dual Plugs the timing can sometimes be staggered. Check Factory figures.. IF much difference the REV drop will vary .  Nev

[BrendAn]

I looked it up. Trigger gaps are adjustable to change timing.

I am going to see if it will climb on either mag. If it does I will leave it alone. If it doesn't will have to look into it.  Trigger gaps should be 20 thou.

[Thruster88]

On my 582 the Rotax needle type tacho shows a drop of 50 rpm one side and 300 the other. There is almost no audible drop on either side, they sound the same. 800 rpm drop would be very dramatic in sound and vibration. Suspect your tacho is telling fibs.

[BrendAn]

35 minutes ago, Thruster88 said:

On my 582 the Rotax needle type tacho shows a drop of 50 rpm one side and 300 the other. There is almost no audible drop on either side, they sound the same. 800 rpm drop would be very dramatic in sound and vibration. Suspect your tacho is telling fibs.

That's my thought too. 

Because it doesn't really run rough.

At 1600 rpm tach reading it should be trying to jump off the airframe but it's not.

[facthunter]

Too large a stagger makes no sense. When on the retarded position it will lose too much power and runs hotter. The faster the Gas burns the better. (Flame travel). Firing them at the same timing achieves this.  IF a plug is not firing that cylinder runs a bit more retarded. 2 strokes can whisker plugs and that can be a transient and correct itself. Nev

[facthunter]

 618's have had crankshaft Issues (Break at the drive end). Don't climb out over trees or over houses. Nev

[BrendAn]

54 minutes ago, facthunter said:

 618's have had crankshaft Issues (Break at the drive end). Don't climb out over trees or over houses. Nev

618 s have the strongest crank of all the 2 smoke Rotax . That's why they weigh more than a 582. The same crank in a 670 runs up to 135 hp.

[BrendAn]

2 hours ago, facthunter said:

 618's have had crankshaft Issues (Break at the drive end). Don't climb out over trees or over houses. Nev

That's the  great thing about where I fly. I always have a farm under me if I have an engine failure.  Although I would try to land on a road if suitable.

[facthunter]

The failures are on record.. Nev

[BrendAn]

1 minute ago, facthunter said:

The failures are on record.. Nev

Where do I find the records. I found a bit about crank bearing failures.

[facthunter]

Look harder (IF you really want to find out). I DON"T have any axe to grind. I was flying 2 strokes then and it was common Knowledge. The 582 quickly became the PREFERRED ENGINE in the 65 Hp range.  I'm careful with all things and have never had a 2 stroke fail. There can always be a first time but the More careful I am, the More Lucky I seem to be. Nev

Edited July 28 by facthunter

[BrendAn]

14 minutes ago, facthunter said:

Look harder (IF you really want to find out). I DON"T have any axe to grind. I was flying 2 strokes then and it was common Knowledge. The 582 quickly became the PREFERRED ENGINE in the 65 Hp range.  I'm careful with all things and have never had a 2 stroke fail. There can always be a first time but the More careful I am, the More Lucky I seem to be. Nev

I don't really care . I just assumed you knew where the record could be found. If you google Rotax rick, the guru of Rotax, he reckons the 618 is the best of the 2 strokes if looked after correctly. He recommends running 40 to 1 . None of his rebuilds have failed and he thinks 40 to 1 is the main reason. I have oil injection but I need to add a bit of oil to the fuel too I suppose.

I was terrified my Jabiru engine would explode but it ran like a Swiss watch.  Read to many internet posts about how bad they were. 

[T510]

There will always be people who make claims with out the evidence to back them up.

 

The people who have the failures tell anyone who will listen, the people with no issues rarely tell anyone.

Majority of the failures are typically linked to poor maintenance.

 

I always ran 2-5% Motul 2 stroke oil as premix in my oil injected 2 strokes, give you a little bit of safety margin if the oil injection system fails

[facthunter]

A bit of extra oil in the fuel is always a good idea with Pumps. Once the Engines are hot the Oil separates from the Fuel better and despite all the talk of fuel/oil ratios  recent  extensive dyno tests have found about 40: 1 is best power output with correct mixture adjusted in all cases.  2  stroke lubing has always been considered MARGINAL needing anti friction bearings everywhere. Normal OILS Lower the Octane by a large amount. Don't use and also TCW3 is for Outboards ONLY. Plug heat range is a bit more critical that other engines too. 2 strokes can detonate. Use high enough octane and don't use stale fuel if mixed. Ring groove Carboning is a cause of ring breakage and sudden failure. You can check that by removing the exhaust pipe. and pushing the rings slightly but the best is to take the Cylinders off  and check.  Pull the prop over and check how the compression feels. . Inverted motors sometimes get stuff on the Plugs  Remove and scrape the Insulator with a Sharpened hairpin.  Chisel point. Nev

[BrendAn]

I am running amsoil interceptor because it is considered the best oil for Rotax. 

And Iridium plugs cross referenced from the stock plugs..

[facthunter]

Bit of a waste of money in my opinion. Insulator foullng is the Main problem, not Point wear and you have Dual ignition. Nev

[BrendAn]

7 minutes ago, facthunter said:

Bit of a waste of money in my opinion. Insulator foullng is the Main problem, not Point wear and you have Dual ignition. Nev

engines run nicer with iridium plugs and there is less load on the ignition itself. not to mention the extra life over stock plugs.

 

[BrendAn]

this is getting annoying. i started this thread about my mag drop and end up defending myself as usual. 

 

nev you say you have no axe to grind yet you do nothing but criticise rotax engines. 

if i listened to you i would not get in an aircraft powered by rotax, just too dangerous.

[facthunter]

That's complete rubbish. You have a lot to learn and the wrong attitude to learning. Hell I've put a lot of effort into Listing  things that Might be some assistance. ALL engines have Faults and idiosyncracies.   What I've said about two strokes applies to all two strokes likely to be in an aeroplane  I've spent a lifetime working on the B'' things and never once mentioned Rotax when flying one. Nev

[BrendAn]

25 minutes ago, facthunter said:

That's complete rubbish. You have a lot to learn and the wrong attitude to learning. Hell I've put a lot of effort into Listing  things that Might be some assistance. ALL engines have Faults and idiosyncracies.   What I've said about two strokes applies to all two strokes likely to be in an aeroplane  I've spent a lifetime working on the B'' things and never once mentioned Rotax when flying one. Nev

so you are saying you have never had a negative thing to say about rotax engines.

[facthunter]

 I  will say what I have learned about any Motor and none of them are perfect, especially Piston engines. A motor that can't be faulted is yet to be built. They are built by Humans. Reciprocating engines have rapid Load reversals. torsional vibrations and can fly apart with great force. Better you know about it and deal./ live with it  or perhaps be FAT, DUMB and Happy with blissful Ignorance I can understand that but don't whinge IF/When you come unstuck. So far it's worked for ME. Haven't injured any person OR Damaged a Plane. I've had a LOT of failures but I didn't CAUSE any of them. Nev

[BrendAn]

10 minutes ago, facthunter said:

 I  will say what I have learned about any Motor and none of them are perfect, especially Piston engines. A motor that can't be faulted is yet to be built. They are built by Humans. Reciprocating engines have rapid Load reversals. torsional vibrations and can fly apart with great force. Better you know about it and deal./ live with it  or perhaps be FAT, DUMB and Happy with blissful Ignorance I can understand that but don't whinge IF/When you come unstuck. So far it's worked for ME. Haven't injured any person OR Damaged a Plane. I've had a LOT of failures but I didn't CAUSE any of them. Nev

i agree with this post .  i look after engines and rarely have a problem. and the day i stop learning is not here yet .