Today's Message Index:
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1. 06:20 AM - Silicone for Spark Plug Threads (michael baker)
2. 06:35 AM - Re: Silicone for Spark Plug Threads (Gilles Thesee)
3. 07:45 AM - Re: Silicone for Spark Plug Threads (ricklach)
4. 09:45 AM - Re: Silicone for Spark Plug Threads ()
5. 12:00 PM - Re: Silicone for Spark Plug Threads (LarryMcFarland)
6. 12:38 PM - Re: Silicone for Spark Plug Threads (Duncan & Ami McFadyean)
7. 04:28 PM - Re: Silicone for Spark Plug Threads (Roger Lee)
Message 1
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| Subject: | Silicone for Spark Plug Threads |
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.
Cheers, Mike.
do not archive
Message 2
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| Subject: | Re: Silicone for Spark Plug Threads |
michael baker a crit :
> 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
Message 3
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| Subject: | Re: Silicone for Spark Plug Threads |
Try Radio Shack, thats where I got mine.
Rick
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=185613#185613
Message 4
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| Subject: | Re: 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?
Message 5
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| Subject: | Re: Silicone for Spark Plug Threads |
Hi Guys,
Ive a Subaru, but plug issues are common to us. I use no seize which
is an anti-lock paste. Its 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@suffolk.lib.ny.us wrote:
>
> Hi Michael
>
> "I was wondering what type of silicone do others use and where do you buy
> it."
>
>
> Ron Parigoris
>
>
Message 6
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| Subject: | Re: 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.
Message 7
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| 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.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=185666#185666
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