2-stroke Spark Plug Installation

Hi Dennis

For sure do NOT use Antiseize on the plugs.  the metallic content of the material can cause issue if it gets on the electrode.  On the 4 strokes the Wacher, which is a silicone heat transfer paste, is required to have the heat drawn away correctly from the plug ot the head.  If you want to use something I would personally recommend it for the same reason on the 2 strokes.  The process is exactly the same as with the 4 stroke in the video.  

Cheers

Thanks for the reply.  I was hoping for a ‘book’ answer.  The 503 parts manual shows where to apply Loctite, lubricants, etc, but no mention of anything on the spark plug threads, on the caps yes, but not the plug threads.  Nothing in Maintenance, Operator’s, or Installation Manuals either.

Crazy thing, I owned a 503 many years ago and do not recall what I used to do, but never had any trouble.  Now I also own a 912, and I use silicone as called out in the manuals.  On the Cessna I had owned, I used Champion Antiseize, and was shown by an A&P how to apply it so none gets into the combustion chamber, as you say, it could short out the electrode.

Guess we are on our own with 2-stroke engines, or perhaps the 912 video in the 2-stroke library of Rotax-Owner implies the new practice is to use silicone on the older 2-stroke engines even though nothing is said in the manuals that we all should be following.

Thanks,

Dennis

Dennis you are right, there is nothing in any of the manuals for the 2 stroke.  We never used anything for decades and it was only after they started to produce 4 strokes that any thought was given to putting something on the threads.  For the most part the required and repetitive spark plug changes was sufficient so we never saw any seized plug threads.  The 4 strokes have to go 100 to 200 hours, 400 on the newer style, before plug change.  That was the main reason that spark plugs have to have something to prevent sticking in the head when you try to remove them after perhaps years of being installed.  

Cheers

It most certainly is in the manual.

Book answer. 582 Line Maintenance chapter 12 page 7, found on this website.

Spark plug mod. 99: Step Procedure 1 Apply a small amount of heat-conducting compound to spark plug threads. 2 Tighten the spark plugs to 27 Nm (20 ft. lb), only on cold engine.

Spark plug mod. 17: Step Procedure 1 Apply a small amount of heat-conducting compound to spark plug threads. 2 Tighten the spark plugs to 16 Nm (142 in. lb), only on cold engine.

It is merely to provide for proper heat conduction, not for corrosion or seizing.

I don’t think there is a line maintenance manual for the 503, but logic would follow that this applies to all the 2-strokes since it is in the 582 line maintenance manual – I see it in your reference.  My main concern was that it might change the heat range of the plug by changing the thermal transfer properties.

What really gets me is that people harp on following the manuals.  Good advice.  Well, that is, except when they advise don’t follow the manual.

My poor memory tells me that I had been using thermal paste for the 503 I owned many years ago, and I will be sure to use it now.  I think the FAA ELSA maintenance course by Rainbow Aviation taught us this as well.   I need to locate my notes.

Many thanks,

Dennis