Iridium plug for stihl trimmer?

[billt460]

For most of us, there are no pump based aviation-grade, zero ethanol, 100 octane unleaded fuels available. Are you near one of the CA airports that is supposed to have GAMU G100UL available by summer 2024?

Yes, GAMI and Swift have products they have developed, and I can't wait to try them.

Why is that? Is lead all that necessary today for modern, piston engine aircraft? If it's the shelf life, that I can somewhat understand. Because a lot of aircraft sit in hangars, and / or are tied down, far more than they are flown.

But one can argue so are boats and motorcycles in temperate Winter climates. And they run fine on unleaded, especially if treated with a good, quality stabilizer like Sta-Bil or Pri-G.

Back in Chicago I had a Toro mower with a Briggs & Stratton engine that sat for over 5 years with a tankful of unleaded 87 treated with Sta-Bil.... And when we moved to Arizona, I pulled it out of the basement, and it started on the second pull.

All of my motorcycles ran much better on unleaded Premium, than they did on leaded. Including my 1978 Kawasaki KZ-1000. Which the dealer told me to ONLY use a leaded Premium. Which I did until it was no longer available.

When I switched it over to unleaded Premium, the plugs lasted far longer. And it wouldn't load up in stop and go city driving. Then misfire until I ran it at a high enough RPM on the highway, long enough to, "clear it out".

I would think most light aircraft piston engines would respond much the same.

 

[97prizm]

For most of us, there are no pump based aviation-grade, zero ethanol, 100 octane unleaded fuels available. Are you near one of the CA airports that is supposed to have GAMU G100UL available by summer 2024?

Yes, GAMI and Swift have products they have developed, and I can't wait to try them.

No I'm in Colorado. My local airport started getting 100 octane mogas unleaded apparently a little while back. It's only available during business hours though. Not sure where they get it. Suncor in commerce city refines alot of DIA's jet fuel and jet fuel in general.

 

[97prizm]

Why is that? Is lead all that necessary today for modern, piston engine aircraft? If it's the shelf life, that I can somewhat understand. Because a lot of aircraft sit in hangars, and / or are tied down, far more than they are flown.

But one can argue so are boats and motorcycles in temperate Winter climates. And they run fine on unleaded, especially if treated with a good, quality stabilizer like Sta-Bil or Pri-G.

Back in Chicago I had a Toro mower with a Briggs & Stratton engine that sat for over 5 years with a tankful of unleaded 87 treated with Sta-Bil.... And when we moved to Arizona, I pulled it out of the basement, and it started on the second pull.

All of my motorcycles ran much better on unleaded Premium, than they did on leaded. Including my 1978 Kawasaki KZ-1000. Which the dealer told me to ONLY use a leaded Premium. Which I did until it was no longer available.

When I switched it over to unleaded Premium, the plugs lasted far longer. And it wouldn't load up in stop and go city driving. Then misfire until I ran it at a high enough RPM on the highway, long enough to, "clear it out".

I would think most light aircraft piston engines would respond much the same.

Tetraethyl lead bumps octane and acts as a lubricant for the valves etc. I think washing state had a program at a few GA airports that pushed unleaded but they ended up with a number of pilots that had engine damage. A new continental or Lycoming can run 30 grand. Not something that you would want to experiment with. However if I had been running Lycoming or Continental I think I would have looked at developing an engine that didn't need lead a decade ago or so.

 

[billt460]

Tetraethyl lead bumps octane and acts as a lubricant for the valves etc. I think washing state had a program at a few GA airports that pushed unleaded but they ended up with a number of pilots that had engine damage. A new continental or Lycoming can run 30 grand. Not something that you would want to experiment with. However if I had been running Lycoming or Continental I think I would have looked at developing an engine that didn't need lead a decade ago or so.

More like a half century ago. I'm not so sure I buy into that whole argument that, "an engine "needs" lead". Here is why. Go back in the 50's and 60's, and even into the early 70's, when all cars ran on heavily leaded fuel, it was very common to have "valve jobs" done in as little as 60,000 miles.

Back then if you got over 100,000 miles on your engine without pulling the heads, it was something you bragged about at the local bar.... Today, with ALL cars running on unleaded, it's not uncommon to have vehicles go well over 200,000 miles without any internal work being done.

Many go 300,000 or more with proper maintenance. Now you don't even have to replace spark plugs until 100,000 miles. With leaded fuel you would be lucky to get 10,000 out of them before they were all fouled out with combustion deposits. All automakers have designed engines that can not only run on unleaded fuel...... They thrive on it.

Why can't Lycoming and Continental do the same? As I said, they've had the last half century or more to do it. I would think it would be far easier and cheaper, than trying to put Diesel engines in new planes that run on Jet-A.

 

[350Rocket]

I saw that Autolite offers an iridium plug for the Stihl FS-38 which I've had for five years. It's been the best trimmer I've ever owned. Does anyone have any experience using an iridium plug on 2-stroke ope? I use high octane gas and or avgas.

I'm curious too because my fs40 has the original plug never removed...I think about 6-7 years now. Never failed to start ever.
Make sure to grease the head bearing assembly...I didn't realize it was greatsable and mine is sloppy now.

 

[tmorris1]

I'd run the Iridium plug. Does Autolite have a sticker you can put on the engine covers?


I just got a Stihl FS70R trimmer a few weeks ago and I can't wait to get enough hours on it so I can pull maintenance.

I've only used it once. For now, I'm running pre-mixed Tru-Fuel; other than ethanol-free and convenience, I see no advantage to paying +$30/gallon for fuel for something that is run once a week. The +92 octane is rather laughable; maybe that's the only way E0 is available? Perhaps the advantage is cooler combustion?

This thing starts on the first pull, even when stone cold. Hopefully, it stays that way.

Reason for premium fuel is mostly the E0 aspect. Very important when you are only running it once a week and not using up a lot of fuel.
I am surprised you haven't had black helicopters descend on you for running a 2-stroke in CA? I thought you couldn't even buy one there?

 

[97prizm]

I'm curious too because my fs40 has the original plug never removed...I think about 6-7 years now. Never failed to start ever.
Make sure to grease the head bearing assembly...I didn't realize it was greatsable and mine is sloppy now.

My fs38 is a curved shaft trimmer. I bougjt Stihl grease but apparently the curved shaft trimmers have to have the engine unbolted to lube the flexible shaft. I know alot of people on here will call shenanigans but i ran my trimmer with the oe plug three times in a row measuring out the gas. I put an E3 Plug in and I was able to eeek out 20 or so minutes longer per tank. My mower was the same.

 

[The_Eric]

More like a half century ago. I'm not so sure I buy into that whole argument that, "an engine "needs" lead". Here is why. Go back in the 50's and 60's, and even into the early 70's, when all cars ran on heavily leaded fuel, it was very common to have "valve jobs" done in as little as 60,000 miles.

Back then if you got over 100,000 miles on your engine without pulling the heads, it was something you bragged about at the local bar.... Today, with ALL cars running on unleaded, it's not uncommon to have vehicles go well over 200,000 miles without any internal work being done.

Many go 300,000 or more with proper maintenance. Now you don't even have to replace spark plugs until 100,000 miles. With leaded fuel you would be lucky to get 10,000 out of them before they were all fouled out with combustion deposits. All automakers have designed engines that can not only run on unleaded fuel...... They thrive on it.

Why can't Lycoming and Continental do the same? As I said, they've had the last half century or more to do it. I would think it would be far easier and cheaper, than trying to put Diesel engines in new planes that run on Jet-A.

I asked a similar question a year or two ago and the response that I got was (if I remember correctly) that it has to do with the design of the engine - a large bore, low speed, high load design that needs a higher resistance to detonation and lead fills that void as there is something chemically that it possesses that other octane adding agents don't.

One of the reasons to keep it is that there are so many of the "older" designed engines in service that will continue to be in service.

 

[paulo57509]

Reason for premium fuel is mostly the E0 aspect. Very important when you are only running it once a week and not using up a lot of fuel.
I am surprised you haven't had black helicopters descend on you for running a 2-stroke in CA? I thought you couldn't even buy one there?

It's odd. Go to the Stihl website and none of the ICE trimmers are available in CA. Yet the local ACE Hardware had four different models, more than a few each. Maybe they're "pre-ban" NOS or they fall below a certain durability and/or displacement rule. The local HD had a wall full of Echo SRM-225's.

 

[350Rocket]

My fs38 is a curved shaft trimmer. I bougjt Stihl grease but apparently the curved shaft trimmers have to have the engine unbolted to lube the flexible shaft. I know alot of people on here will call shenanigans but i ran my trimmer with the oe plug three times in a row measuring out the gas. I put an E3 Plug in and I was able to eeek out 20 or so minutes longer per tank. My mower was the same.

I will probably try that plug when I replace it. It's felt slightly more rough running than it used to but still starts easily.
I found a replacement bearing housing for the end for $21 on Amazon. It looks correct but the original is holding together for now. You have to remove the plastic guard and a little bolt to access and pump grease in and I wasn't aware. The fs38/40 are pretty similar.

 

[97prizm]

It's odd. Go to the Stihl website and none of the ICE trimmers are available in CA. Yet the local ACE Hardware had four different models, more than a few each. Maybe they're "pre-ban" NOS or they fall below a certain durability and/or displacement rule. The local HD had a wall full of Echo SRM-225's.

I think their ban is Jan 01, 2025 if I remember correctly. They had to BACKPEDAL alot after 20 thousand lawn care companies said " what about us" oh yeah "free" vouchers on the taxpayers dollars won't cut it. Colorado tried to pull this but backed off. Stihl offers catalytic converters on their chain saws to reduce pollution. They claim no performance penalty.

 

[97prizm]

I asked a similar question a year or two ago and the response that I got was (if I remember correctly) that it has to do with the design of the engine - a large bore, low speed, high load design that needs a higher resistance to detonation and lead fills that void as there is something chemically that it possesses that other octane adding agents don't.

One of the reasons to keep it is that there are so many of the "older" designed engines in service that will continue to be in service.

Alot of it has to due with FAA certification as well. This is why the homebuilt market has boomed.
Hetes a synopsis of why leaded fuel iscstill used. Remember GA aircraft are air cooled like a vw bug. VW hit a wall and built a prototype bug that was water cooled to pass emissions but they eventually scrapped the idea.
"
Dependability

The most common leaded fuel found in aviation is 100LL. The lead added to the fuel helps it achieve a higher octane level. High-octane fuel is preferred for general aviation because it is more stable and prevents detonation in the aircraft’s cylinders. Over time, detonation can take a toll on aircraft engines and cause undue wear and tear. This could adversely affect the safety of the occupants if a mechanical incident were to occur.



Difficulty in permitting other fuel use

Most general aviation aircraft need a supplemental type certificate (STC) to operate on unleaded fuel. A STC is a certificate granted by the Federal Aviation Administration (FAA) for any modifications to an aircraft. Since most general aviation aircraft were not permitted to use fuel besides 100LL at the time of manufacturing, the STC is required to legally operate an aircraft on unleaded fuel. These certificates can be pricey. A STC for unleaded fuel can cost $500-1,000. In addition, there are very few fuels approved for use with the STCs and they are hard to come by.
Widely available

100LL can be found at most airports across the country. Most airports do not carry unleaded aviation fuel. The select few airports that do have unleaded fuel, the supply is low compared to the large storage and supply of 100LL.

 

[97prizm]

I will probably try that plug when I replace it. It's felt slightly more rough running than it used to but still starts easily.
I found a replacement bearing housing for the end for $21 on Amazon. It looks correct but the original is holding together for now. You have to remove the plastic guard and a little bolt to access and pump grease in and I wasn't aware. The fs38/40 are pretty similar.

Is there a diagram somewhere? The geared trimmers have a port where the Stihl grease tube threads in. I was told the curved shaft models couldn't be lubed.

 

[Rygrego]

I'd like to hear how the Av Gas works in a 2 stroke.

Av gas works fine in a two stroke. I ran av gas and AeroShell mixed in my two stroke helicopter for years.

 

[SHOZ]

I bought a Denso twin tip iridium for my mower and it's limited to about .030' as the narrow gap, any narrower and it changes to an offset not straight down.

 

[350Rocket]

Is there a diagram somewhere? The geared trimmers have a port where the Stihl grease tube threads in. I was told the curved shaft models couldn't be lubed.

This video explains it. I stumbled across one of these videos and that's when I realized I messed up.

 

[Cujet]

Why is that? Is lead all that necessary today for modern, piston engine aircraft? If it's the shelf life, that I can somewhat understand. Because a lot of aircraft sit in hangars, and / or are tied down, far more than they are flown.

But one can argue so are boats and motorcycles in temperate Winter climates. And they run fine on unleaded, especially if treated with a good, quality stabilizer like Sta-Bil or Pri-G.

Back in Chicago I had a Toro mower with a Briggs & Stratton engine that sat for over 5 years with a tankful of unleaded 87 treated with Sta-Bil.... And when we moved to Arizona, I pulled it out of the basement, and it started on the second pull.

All of my motorcycles ran much better on unleaded Premium, than they did on leaded. Including my 1978 Kawasaki KZ-1000. Which the dealer told me to ONLY use a leaded Premium. Which I did until it was no longer available.

When I switched it over to unleaded Premium, the plugs lasted far longer. And it wouldn't load up in stop and go city driving. Then misfire until I ran it at a high enough RPM on the highway, long enough to, "clear it out".

I would think most light aircraft piston engines would respond much the same.

Well made aircraft engines run wonderfully on Ethanol Free Unleaded. We use VP C9, (96 octane R+M/2 ) in the turbocharged Rotax 914. There could not be a more perfect fuel for the application.

While some of the older dinosaurs, er, ah, Lycoming engines, do CURRENTLY tend to have exhaust valve issues with unleaded. There are many opinions as to why, but one thing has become clear, it is NOT due to the lack of hardened valve seats. As the flight schools and many other users, that have had the failures did have the updated components.

One hypothesis is that the 94 octane unleaded Avgas is causing the issue due to inadequate real-world octane, despite the engine requirement being 80 octane (fuel spec is 80/87 lean/rich)

Remember that NASCAR went through the same thing. Eventually finding a combination of ultra-exotic exhaust valve components that worked well.

Citing Valve Damage, UND Drops Unleaded Fuel And Returns To 100LL

"After an extensive trial, the University of North Dakota’s flight school has dropped Swift UL94 fuel and resumed use of 100LL. The school said ongoing maintenance monitoring of aircraft using UL94—almost exclusively Lycoming-powered Piper Archers and Seminoles—resulted in measurable exhaust...

www.pilotsofamerica.com

 

[Cujet]

I'd like to get back on topic though. Two stroke engines tend to do quite well with fine wire electrode spark plugs. The reason is not just for "anti fouling" as that problem seems to be in the past. The reason is that 2 stroke engines have poor fuel/air (and exhaust dilution) mixtures under some operational conditions and the fine wire plugs allow better flow around the electrode. In the end, the number of misfires is slightly reduced with the correct application of fine wire plugs.

Both electrodes are typically reduced in size, and the gap is generally larger. I always use the fine wire plugs in my high performance two strokes.

 

[repairman54]

2x, the fine wire plugs are less likely to foul on cold starts. That's my experience with cold starts in snowmobiles. Plus they heat up faster and burn off those deposits. Last carb snowmobile I had, a 700cc twin, plugs were in it for 7000 miles when I sold it. NGK's

 

[Astro_Guy]

I saw that Autolite offers an iridium plug for the Stihl FS-38 which I've had for five years. It's been the best trimmer I've ever owned. Does anyone have any experience using an iridium plug on 2-stroke ope? I use high octane gas and or avgas.

How did you determine this? I couldn't find a recommendation on the Autolite website. I have two pieces of Stihl equipment that are candidates for an Iridium upgrade if one exists.

Is it this:

https://www.autolitesparkplugs.com/autolite-xst2974-xtreme-start-spark-plug

?