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Silicone for Spark Plug Threads

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mbee1(at)mac.com
Guest

Posted: Sat May 31, 2008 5:20 am Post subject: Silicone for Spark Plug Threads

Rotax service information states that  'the application of a silicone heat conduction compound is necessary as itimproves heat transfer between spark plug and cylinder head.'  I was wondering what type of silicone do others use and where do you buy it. Also would Champion Spark Plug lube give the same heat transfer.

Cheers, Mike.

do not archive

Gilles.Thesee(at)ac-greno
Guest

Posted: Sat May 31, 2008 5:35 am Post subject: Silicone for Spark Plug Threads

michael baker a écrit :

 	  Quote: 	
		   Rotax service information states that  'the application of a silicone 

 heat conduction compound is necessary as it

 improves heat transfer between spark plug and cylinder head.'  I was 

 wondering what type of silicone do others use and where do you buy it. 

 Also would Champion Spark Plug lube give the same heat transfer.


	


Michael,



Good question indeed.

Rotax advises the use of a heat transfer compound such as is used for 

electronic components. The idea is rather odd, since the threads 

transfer only about 20% of the heat to the cylinder head.

So even with a 50% improvement due to compound, heat transfer will 

increase only 10 %...Not much.

Nevertheless, such compound can be purchased from any electronic dealer.



The French Rotax dealer sells copper based spark plug lube in lieu of 

heat transfer compound.

It sure helps preventing seizure, but does little toward improving heat 

transfer...But he says everyone is happy with it, so the actual compound 

does not matter much, after all.

The Rotax don't really need any antiseize compound, since the heads are 

way cooler than the Lyco/Conti heads. Never experienced any problem with 

plugs on a Rotax.



Some info on Rotax plugs here

http://contrails.free.fr/engine_tighten.php

Only in French for the moment, sorry.



In my opinion, proper cooling is much much more important for engine 

life than any compound we could use on the plug threads.

FWIW,



Best regards,

-- 

Gilles

http://contrails.free.fr

ricklach

Joined: 20 Jun 2006
Posts: 127
Location: Kernville, Calif.

Posted: Sat May 31, 2008 6:42 am Post subject: Re: Silicone for Spark Plug Threads

Try Radio Shack, thats where I got mine.



Rick

rparigor(at)suffolk.lib.n
Guest

Posted: Sat May 31, 2008 8:45 am Post subject: Silicone for Spark Plug Threads

Hi Michael



"I was wondering what type of silicone do others use and where do you buy

it."



I talked with the guy who did research for Rotax on silicone thermal

conductive compound to use on spark plugs. He said hands down winner was

what Rotax sells. I forget the name of Mfg. but he said stuff you purchase

from Radio Shack or most Electronic supply houses does not fare well. He

was on mission to find alternative to what Rotax offers and in smaller

quantities. Could not find an acceptable substitute. I was read many names

he tested from a quite impressive list. I did read a while back someone in

Europe was able to procure form Mfg. direct, think in Germany.



I agree with Gilles that proper cooling is paramount, followed very close

by not running too lean when you are making some BTUs. Spark plug cooling

is a pretty important issue as well. Let the tip of the plug get too hot

and it can act like a glow plug and cause detonation. Worst case is

preignition that will trash a motor making BTUs in short order. Run too

cold and carbon can build up and fouling/misfiring is very likely.



The spark plug Mfg. for 914 plugs recommends not using anything on threads

at all. That said Rotax recommends their reccomended silicone thermal

conductive compound be used. I for one am willing to follow the Rotax

suggestion on my engine. The research guy for Rotax said only use what

Rotax sells. If by chance I did any testing and found anything I thought

was at least as good, please send him a sample he wants to know about it.



I for one am willing to listen very close to what the manufacturer and

researcher has to say and follow their instructions with my 914. 



Yes Rotax paste is expensive, one idea is go in with 3 others and each

will have a lifetime supply.



When the chips are low 50 feet above the end of the runway and all my

coolant decides to depart, or just running hot due to a high density

altitude and more alcohol than the pump says, I am happy to know that the

tip of my plugs are a bit cooler than using nothing or the wrong product.



Ron Parigoris



BTW if you dig in Rotax documentation, on 914 they want you to do a test

to make sure that the leanest cylinder is running rich enough at full

power. Their procedure is to measure carbon monoxide. I know of no one

including Authorized Rotax Repair facilities who do this. Anyone out there

have a machine (like what Eastwood sells) and plumbing to test?

larry(at)macsmachine.com
Guest

Posted: Sat May 31, 2008 11:00 am Post subject: Silicone for Spark Plug Threads

Hi Guys,



I’ve a Subaru, but plug issues are common to us. I use “no seize” which 

is an anti-lock paste. It’s got very good thermal conductive properties 

and you need not worry about galling threads at some point during 

removal and reinstall. They need light and sensitive fingers for the 

initial turn-in and then torque to spec. Not sure of whether it

has a silicone base or not.



Good luck,



Larry McFarland 601HDS at www.macsmachine.com



rparigor(at)suffolk.lib.ny.us wrote:

 	  Quote: 	
		   



 Hi Michael



 "I was wondering what type of silicone do others use and where do you buy

 it."

 Ron Parigoris

ami(at)MCFADYEAN.FREESERV
Guest

Posted: Sat May 31, 2008 11:38 am Post subject: Silicone for Spark Plug Threads

Not having the benifit of access to the research/testing done on the 

alternatives, why would copperslip be inferior? Copper is a far better 

conductor than the glass (?) used in normal silcone heat sink compounds. 

Except that the carrier grease probably boils off and its use is frowned 

upon in automotive cirlces (because excessive use can contaminate catalytic 

converters).

Or has Rotax found the copper to be incompatable with the Nikasil cylinder 

linings?



Duncan McF.

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Sat May 31, 2008 3:25 pm Post subject: Re: Silicone for Spark Plug Threads

Hi Guys,



Buy your plug paste at Lockwood. They sell a small squeeze tube for about $1.38 that will last 2-3 plug changes. The paste is for the 4 strokes. Don't over apply and don't get it on the plug tip. The plug paste will also help to prevent galling. Do not use anti-seize as it is very different. The transfer heat paste will help keep the plugs operating at their proper heat range.

Number one cause for Rotax engine failures whether it be a 4 or 2 stroke engine (especially 2 stroke) is owner/operator changing specs for what Rotax spent hundreds or even millions of dollars for over the years in research and development. They have  hundreds of thousands of hours if not millions of hours on engines to prove their theories. The owner operator usually has less than a hundred hours and is willing to spend $100 to change a Rotax design.

The Rotax 2 stroke is a very dependable engine so long as you leave it stock and load the engine with the prop correctly.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

Catz631(at)aol.com
Guest

Posted: Sun Jun 01, 2008 5:23 am Post subject: Silicone for Spark Plug Threads

Roger is right. I bought a small packet of it when I went thru Rotax school  at Lockwood. I asked the same question in class about using champion anti  seize (or any other compound) on the plugs and was informed not to use it.  The Rotax silicone stuff is dirt cheap from Lockwood and lasts a long  time.

                                                         Dick Maddux

                                                         Fox4-1200

                                                        912  UL                                                



Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food.

  [quote][b]

Thom Riddle

Joined: 10 Jan 2006
Posts: 1597
Location: Buffalo, NY, USA (9G0)

Posted: Mon Jun 02, 2008 3:20 am Post subject: Silicone for Spark Plug Threads

WHY does Lockwood say not to use Champion or equivalent anti-seize

compound on spark plug threads in Rotax 9 series engines? Without

knowing why, I think I'll continue to use what I've been using

successfully on spark plug threads for over 30 years including many

hundreds of hours on 912 engines.

_________________
Thom Riddle
Buffalo, NY (9G0)

Don't worry about old age... it doesn't last very long.
- Anonymous

Roger Lee

Joined: 10 Jan 2006
Posts: 1464
Location: Tucson, Az.

Posted: Mon Jun 02, 2008 5:37 am Post subject: Re: Silicone for Spark Plug Threads

Hi Thom,



Because anti-seize is a different compound. It was designed just so surfaces would not bond and make items hard to remove. It wasn't designed to be a heat conductor. Just like the plug paste primary roll is not to be an anti-seize compound. Are you using the anti-seize to help prevent galling or for heat transfer? How do you know you are using it successfully? How can you qualify or measure that?  Car engines are not the same as a Rotax and have different heating and cooling properties in different areas. They may have different metallurgy and heat distribution at the plug and head contact points in these engine, too.

The plug paste is dirt cheap. A small squeeze tube that will last 2-3 changes cost about $1.38 and a big tube that will last a life time for you and your friends is about $13.

I'm not always on the book side of the Rotax manual, but this one is too easy to comply with and it's not expensive. I have and still am coming full circle here myself and coming to terms that I have not always done the right thing for the right reasons. I have realized the amount of money, total hours and science that Rotax has invested over twenty years of the 912's existence. It may seem to work on the surface, but our changes to the engine are sometimes misguided. I will be the first person in this line of misguidance, but I am walking a new path now.

You go to enough schools and see enough engine issues caused by the user and the new path was easier to see.

_________________
Roger Lee
Tucson, Az.
Rotax Instructor & Rotax IRC
Light Sport Repairman
Home 520-574-1080 TRY HOME FIRST
Cell 520-349-7056

rparigor(at)suffolk.lib.n
Guest

Posted: Mon Jun 02, 2008 3:38 pm Post subject: Silicone for Spark Plug Threads

Hi Duncan

 

 	  Quote: 	
		   Not having the benifit of access to the research/testing done on the 

 alternatives, why would copperslip be inferior? Copper is a far better 

 conductor than the glass (?) used in normal silcone heat sink compounds. 

 Except that the carrier grease probably boils off and its use is frowned 

 upon in automotive cirlces (because excessive use can contaminate catalytic 

 converters).

 Or has Rotax found the copper to be incompatable with the Nikasil cylinder 

 linings?


	


According to Rotax one problem is many of the compounds that were tested

would disappear real fast. The stuff that Rotax sells supposedly if you

got a dab on the tip, it would be there after 100 hours.



I know some anti sieze compounds have glass in them, probably not a good

idea to run through your motor. 



Ron Parigoris

imap8ntr(at)cox.net
Guest

Posted: Mon Jun 02, 2008 4:34 pm Post subject: Silicone for Spark Plug Threads

I know on the Jabiru engine (just FYI) recommends NOT to use copper 

antiseize I think because it can actually merge with the alloys in the 

engine block.  They recommend to use NICKEL antiseize which I have without a 

problem.  Of course the alloys in the Rotax engine may not be the same as 

the Jabiru.



Ivan

---

Catz631(at)aol.com
Guest

Posted: Tue Jun 03, 2008 4:50 am Post subject: Silicone for Spark Plug Threads

Thom,

    Roger is right on the money ! The instructor Dean at Lockwood  said pretty much the identical thing . I too have been using Champion anti  seize for over 35 years on all my Cont/Lycs but this is a heat transfer paste  not an anti seize (although it is that too) Rotax specifies its use on the 900  series and it is cheap .Us "old farts" can still learn to change our ideas from  time to time.

                                                             Dick Maddux

                                                             Rotax 912 UL



Get trade secrets for amazing burgers. Watch "Cooking with Tyler Florence" on AOL Food.

  [quote][b]

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